FRCA anatomy

Question 1

Where in the skull is the foramen magnum found? (1 mark)

Answer 1

Posterior cranial fossa; basilar part of the occipital bone

Question 2

Name four structures that pass through the foramen magnum (4 marks)

Answer 2

1. Osteo-ligamentous structures:
   • Tip of odontoid process
   • Ligaments (apical ligament, superior band of cruciate ligament, tectorial membrane)
2. Neurovascular structures:
   • Lower end of medulla (with meninges)
   • Cerebellar tonsils (variant)
   • Spinal roots of CN 11 (either side, within subarachnoid space) • Vertebral arteries
   • Anterior and posterior spinal arteries (within subarachnoid space) (Anterior/posterior atlanto-occipital membranes attach to the margin of foramen magnum)

*The osteo-ligamentous structures lie anterior to the alar ligaments, and the neurovascular structures lie posteriorly

Question 3

Name three types of brain herniation (3 marks)

Answer 3

1. Subfalcine (cingulate),A
2. uncal (transtentorial) D and
3. tonsillar (cerebellar) E

(Others: transcalvarial, central transtentorial, upward transtentorial)
○ CN 3 palsy: dilated pupil (initially, loss of parasympathetic supply to pupil), ‘down and out’ (loss of supply to superior/medial inferior rectus and inferior oblique)
° CN 6 palsy: failure of lateral gaze/convergent squint (loss of supply to lateral rectus)

Question 4

Why may ocular features be a false-localising sign in brain injury causing cerebellar herniation? (2 marks)

Answer 4

○ CN 3: may be compressed on margin of tentorium cerebelli by concurrent herniation of uncus
○ CN 6: has a long intracranial course, compressed by oedema in many intracranial locations

Question 5

Describe the pathophysiological changes of tonsillar (cerebellar) herniation (aka coning) (5 marks)

Answer 5

Raised intracerebral pressure (ICP) results in raised mean arterial pressure (MAP) to maintain cerebral perfusion pressure
(CPP)
(CPP = MAP- ICP)

Eventually, raised ICP causes downward displacement of cerebellar tonsils
• As they pass into the foramen magnum, the lower brainstem (medulla and pons) is compressed, with resulting dysfunction of the cardiac and respiratory centres
○ Initial pontine ischaemia results in a hyperadrenergic state (to maintain brainstem perfusion)
• Cushing’s reflex (may only be present in one-third) suggests coning is imminent and describes:
* Hypertension (to maintain brainstem perfusion)
* Bradycardia (reflex baroreceptor activation due to hypertension +/midbrain activation of the parasympathetic nervous system)
* Abnormal respiration (dysfunction of respiratory centre)

After herniation/neuronal death, the loss of spinal cord sympathetic discharge results in vasodilation, bradycardia and impaired contractility (with resultant cardiovascular instability)

Other dysfunction ensues:
• Pituitary ischaemia may result in diabetes insipidus (DI)
• Hypothalamic dysfunction may lead to loss of thermoregulation (compounded by vasodilation, reduced basal metabolic rate and hypothyroidism)

• Coagulopathy (catecholamine effects on platelets, hypothermia and release of plasminogen activator due to neuronal death)

Question 6

What hormone supplementation may be required in such patients if they are considered for brainstem death organ donation? (5 marks)

Answer 6

○ Vasopressin (to maintain cardiovascular stability and for DI, noradrenaline is generally avoided)

○ Methylprednisolone (to reduce neurogenic pulmonary oedema)

○ Thyroid hormone (to maintain cardiac function)

○ Desmopressin (if DI persists despite the use of vasopressin)

○ Insulin (to combat hyperglycaemia resulting from catecholamine release, IV dextrose used to replace water in DI and steroids)

Question 7

What awake surgical procedures are permitted by the use of an axillary block?
(2 marks)

Answer 7

Procedures below the elbow: forearm, wrist and hand

Question 8

Name the nerves targeted when performing this block and where they are found (4 marks)

Answer 8

1. Musculocutaneous nerve (fascial plane between short head of biceps and coracobrachialis) 2. Median nerve (superolateral to the axillary artery, 9–12 o’clock position)
2. Ulnar nerve (inferomedial to axillary artery, beneath axillary vein, 2–3o’clock position)
3. Radial nerve (deep to axillary artery, 4–6o’clock position)

Question 9

Name the nerves targeted when performing this block and where they are found (4 marks) Axillary nerve block

Answer 9

○ Musculocutaneous nerve (fascial plane between short head of biceps and coracobrachialis)

○ Median nerve (superolateral to the axillary artery, 9–12 o’clock position)
○ Ulnar nerve (inferomedial to axillary artery, beneath axillary vein, 2–3o’clock position)

○ Radial nerve (deep to axillary artery, 4–6o’clock position)

Question 10

Regarding the musculocutaneous nerve
How can a block of this nerve be supplemented? (3 marks)

Answer 10

By blocking the nerve at the level of the lateral epicondyle, between the lateral border of biceps and brachioradialis, where it can be seen on ultrasound adjacent to the cephalic vein

Question 11

Regarding the musculocutaneous nerve
What does it supply?

Answer 11

○ Motor supply: biceps, brachialis and coracobrachialis

○ Sensory supply: lateral forearm (via its continuation as the lateral cutaneous nerve of forearm)

Question 12

Regarding the musculocutaneous nerve
Why may it be missed during an axillary brachial plexus block?

Answer 12

Because it leaves the brachial plexus in the proximal axilla (therefore lies in a separate fascial plane at this level in 70% of the population, thus it should be blocked separately)

Question 13

What pattern of missed segment(s) is demonstrated in an inadequate axillary block? What areas are most likely to be spared in patients and why? What can be done to remedy this? (5 marks)

Answer 13

Because the block is performed at the level of the terminal branches of the brachial plexus, missed segments demonstrate a nerve territory distribution (rather than dermatomal)
°Medial side of forearm and (especially) arm, because:
○ Intercostobrachial nerve (lateral cutaneous branch of T2) supplies skin over the medial proximal arm and is not blocked
○ Medial cutaneous nerves of arm and forearm are branches of the medial cord of the brachial plexus in the axilla (before the ulnar nerve is given off) and therefore may be missed if not blocked separately

○ A subcutaneous injection of local anaesthetic in the medial proximal arm (or guided by ultrasound to target the medial cutaneous nerves of arm/forearm) can be performed

• Brachial plexus block provides superior tourniquet coverage compared to distal nerve blocks (muscle ischaemia is the main problem)– this is an important consideration for upper limb surgery, in addition to covering the surgical site

Question 14

Describe a technique for performing an ultrasound-guided axillary brachial plexus block (6 marks)

Answer 14

Stop before you block: confirm side and site SLIMRAG*:
• Sterile procedure (wash hands, sterile gloves, sterile dressing pack)
• Light source/ultrasound IV access
• Monitoring (AAGBI minimum standard)
• Resuscitation drugs/equipment available
• Assistant (who is happy to assist with regional or general anaesthetic)
• General anaesthetic (ensure equipment/drugs available to convert if required)

1. Position the patient supine, upper limb abducted and externally rotated, elbow flexed at 90°
2. Clean the field with 0.5% chlorhexidine and allow to dry
3. High-frequency linear array transducer applied transversely across the axilla at the junction of biceps brachii and pectoralis major (with sterile cover and gel on probe)
4. Local anaesthetic to skin, then in-plane technique, blunt 22 G 50–80 mm block needle from lateral side of upper limb (can also be done out of plane)
5. Block the four nerves using sonoanatomy landmarks of axillary artery and vein
6. After negative aspiration slowly inject 25–30 ml of local anaesthetic, targeting each nerve
7. Can augment by block of intercostobrachial +/medial cutaneous nerves of arm/ forearm

Question 15

Describe the structure of the respiratory tree (10 marks)

Answer 15

The trachea bifurcates at the carina (plane of the sternal angle, T4–T4/5) into primary bronchi (left and right)
○ Right primary (or main) bronchus: Shorter, wider and more vertical
Azygos vein arches forwards over the bronchus
Divides into three secondary (lobar) bronchi:
• superior, middle and inferior N.B.
• Superior lobar bronchus (eparterial bronchus) is given off before the hilum of the lung
○ Left primary (or main) bronchus: Longer, narrower and more horizontal
•Passes beneath the arch of the aorta
• Passes immediately in front of (and indents) the oesophagus and descending thoracic aorta
• Divides into two secondary (lobar) bronchi: superior and inferior
○ The secondary bronchi divide into tertiary (segmental) bronchi

•These each supply a bronchopulmonary segment
: Right:
● Upper lobe: apical, anterior, posterior
● Middle lobe: medial, lateral :
● Lower lobe: apical, medial/lateral/anterior/posterior basal
○ Left:
● Upper lobe: apical, anterior, posterior, lingular (superior and inferior)
● Lower lobe: apical, medial*/lateral/anterior**/posterior basal

On average, the right side has 10 segments, left has 8–10

○ Tertiary (segmental) bronchi divide into many smaller bronchioles

Ultimately terminal bronchioles arise (1 mm diameter, no cartilage in wall)
• These give rise to respiratory bronchioles (lose respiratory epithelium)
• From these, alveolar ducts arise, and from these, alveolar sacs (which are clusters of alveoli)
• In total there are 23 divisions of the bronchial tree

• The first 17 form part of the conducting zone (finish at terminal bronchioles)
•Generations 18–23 form part of the respiratory zone (start at respiratory bronchioles)

• and ** often conjoined, hence the variable (often fewer) number of bronchopulmonary segments quoted for the left lung

Question 16

Which segment(s) of which lung is most likely to be affected by aspiration of gastric contents (3 marks)

Answer 16

More likely on right (as right main bronchus is shorter, wider and more vertical) Depends on position:
• Supine: apical segment of right lower lobe
• Standing/sitting: posterior basal segment of right lower lobe
• Lying on right: right middle lobe or posterior segment of right upper lobe

Question 17

Describe the pathophysiology of aspiration pneumonitis (3 marks)

Answer 17

Large particles cause acute airway obstruction +/lobar collapse and atelectasis Initial changes due to acute inflammatory response resulting from chemical irritation (aspiration pneumonitis due to haemorrhagic tracheobronchitis and pulmonary oedema)

The most likely complication is acute respiratory distress syndrome (ARDS) (infection may or may not result)

Question 18

) How do you manage aspiration in a patient with a supraglottic airway device? (4 marks

Answer 18

1. Call for help and ask surgeon to stop (only restart if patient stable +/emergency surgery)
2. FiO2 to 1
3. Move patient to left lateral position (if possible, head down) Suction oropharynx, down lumen (if a second-generation supraglottic airway device (SAD) is being used, suction down the gastric port +/pass a narrow bore NG tube to aspirate/decompress the stomach)
4. If major airway contamination/desaturation: consider intubation, positive pressure ventilation, bronchoalveolar lavage, bronchodilators, ITU post-op
5. If minimal: ensure SAD correctly placed, airway is clear and patient is adequately anaesthetised, then CXR in recovery (only antibiotics if subsequently develops infection)

Question 19

Describe the boundaries of the epidural space (4 marks)

Answer 19

○ Extends from the foramen magnum superiorly to the sacral hiatus (sacrococcygeal membrane) inferiorly
○ Anteriorly: the vertebral bodies and intervertebral discs, covered by the posterior longitudinal ligament

○ Laterally: the pedicles and the intervertebral foramina

○ Posteriorly: the laminae of the vertebral arches, the capsules of facet joints and ligamenta flava

Question 20

List the contents of the epidural space (6 marks)

Answer 20

○ Dural sheath/sac and contents (arachnoid mater, subarachnoid space and CSF, pia mater, spinal cord/spinal nerve roots and spinal arteries/veins)
○ Spinal nerve roots (within a sleeve of dura/arachnoid)
○ Filum terminale (beyond the termination of the dural sac at S2)
○ Vessels: (Anterior and posterior) radicular arteries
○ Internal vertebral venous plexus of Batson
○ Lymphatics
○ Loose areolar tissue* (fat content varies in direct proportion to the rest of the body)
○ Connective tissue**
*Apparently this is not uniform in distribution and exists in bands at the levels of intervertebral foramina
**A median fold of dura has been reported and would explain the occasional unilateral effect of epidural analgesia)

Question 21

What structures does the Tuohy needle pass through when performing a midline epidural? (5 marks)

Answer 21

○ Skin
○ Subcutaneous tissue/superficial fascia ○ Supraspinous ligament
○ Interspinous ligament
○ Ligamentum flavum (ligamenta flava lie either side of the midline, between laminae of two adjacent vertebrae, but may be fused in the midline)

Question 22

What are the benefits of epidural analgesia after laparotomy for malignant disease? (5 marks)

Answer 22

○ Short term:
•Lower pain scores
•Reduce opioid consumption (and associated side effects: respiratory depression, nausea/vomiting, immunosuppression)
•Reduced stress response, sympathetic activation and immunosuppression
•Lower transfusion requirements •Reduced incidence of respiratory failure and postoperative pneumonia
•Reduced incidence of DVT/PE

Long term:
•Reduced metastatic spread

Question 23

Describe the boundaries and contents of the femoral triangle (6 marks)

Answer 23

○ Superior: inguinal ligament
○ Lateral: medial border of sartorius
○ Medial: medial border of adductor longus
○ Roof:fascia lata (and cribriform fascia at saphenous opening), skin/subcutaneoustissue

○ Floor: iliacus, psoas major, pectineus, adductor longus

○ Contents: Femoral nerve
• Femoral sheath, containing: :
○ Femoral artery (and branches) :
○ Femoral vein (and tributaries, including long saphenous vein) :
○ Femoral canal (containing lymphatics/deep inguinal lymph nodes, including node of Cloquet)

Question 24

What is a fascia iliaca block? (2 marks)

Answer 24

It is a compartment block where local anaesthetic is deposited into the plane between the deep fascia overlying the iliacus muscle, where several branches of the lumbar plexus are found (femoral nerve courses through a pocket of the fascia iliaca)
○ Therefore, a large volume of local anaesthetic is required (e.g. 30 ml)

N.B. Obturator nerve (L2–4, supplying hip, medial/adductor compartment of thigh and skin of medial thigh/knee)– block is described in fascia iliaca technique, but rarely occurs as the nerve emerges on the medial side of psoas major

Question 25

Describe the borders of the fascia iliaca compartment and nerves affected by the block (6 marks)

Answer 25

• Anterior: fascia iliaca • Posterior: anterior surface of iliacus and psoas major/their conjoint tendon • Medial: linea terminalis/pelvic brim ○ Lateral: inner lip of iliac crest Nerves: • Femoral nerve (L2–4): supplies hip, anterior/extensor compartment of this, skin of anterior thigh/medial leg and medial foot to first MTPJ • Lateral cutaneous nerve of thigh (L2–3): supplies skin of anterolateral thigh

Question 26

Describe how you would perform a fascia iliac block (6 marks)

Answer 26

Consent Stop before you block: confirm side and site SLIMRAG: • Sterile procedure (wash hands, sterile gloves, sterile dressing pack) • Light source/ultrasound IV access • Monitoring (AAGBI minimum standard) • Resuscitation drugs/equipment available • Assistant (who is happy to assist with regional or general anaesthetic) • General anaesthetic (ensure equipment/drugs available to convert if required)

Question 27

Describe the origin, course and termination of the internal jugular vein (IJV). Make specific reference to its relationship with the carotid artery (5 marks)

Answer 27

Emerges through the posterior compartment of the jugular foramen as a continuation of the sigmoid sinus (Origin sometimes described as the point where it combines with the inferior petrosal sinus) Lies posterior to the internal carotid artery at the base of the skull (on the transverse process of the atlas) As it passes inferiorly in the neck, it comes to lie on the lateral side of the internal carotid artery In the lower neck, the IJV typically lies anterior/anterolateral to the common carotid artery Terminates behind the medial end of the clavicle, joining with the subclavian vein to form the brachiocephalic vein

Question 28

Describe features that distinguish the jugular venous pulse (JVP) from the carotid pulse (5 marks)

Answer 28

○ JVP is impalpable ○ JVP has a complex waveform ○ JVP fills from the top (if IJV occluded) ○ JVP demonstrates the hepatojugular reflux (JVP will transiently rise with hepatic pressure) ○ JVP moves with respiration (normally decreasing on inspiration and rising in expiration)

Question 29

List five indications for cannulating the IJV (5 marks)

Answer 29

○ Monitoring CVP/RV function/intravascular volume status ○ Administration of drugs that cannot be given peripherally (vasoactive drugs/inotropes, vaso-irritant drugs, e.g. potassium/amiodarone, total parenteral nutrition (TPN), some cytotoxic drugs) ○ Blood sampling due to poor vascular access ○ Insertion of pulmonary artery catheter (or its introducer sheath for large-bore IV access +/rapid fluid administration) ○ Haemodialysis/haemofiltration ○ Transvenous cardiac pacing ○ Aspiration of air embolus from right-hand side of the heart Jugular venous bulb saturation measurement

Question 30

List five complications of cannulating the IJV (5 marks)

Answer 30

Due to needle: • Carotid artery puncture (+/bleeding, dissection, embolus) • Pneumothorax (or haemothorax) • Thoracic duct injury (+/chylothorax) • Nerve injury (e.g. CN 10, recurrent laryngeal, phrenic) Due to line: • Arrhythmia • Air embolism • Thrombosis/embolism (+/vessel stenosis) •Infection • Cardiac tamponade/haemopericardium 52 • Anaphylaxis has been reported from chlorohexidine-impregnated catheters

Question 31

Name the tissue layers traversed during insertion of an intercostal (chest) drain (5 marks)

Answer 31

○ Skin ○ Superficial fascia ○ External intercostal muscle ○ Internal intercostal muscle ○ Inner most intercostal muscle ○ Endothoracic fascia ○ Parietal pleura

Question 32

Name and describe the muscles of the intercostal space (6 marks)

Answer 32

○ External intercostal: •Outermost layer, fibres pass downwards and forwards from sharp inferior border of rib • Extends from tubercle of rib (posteriorly) to costochondral junction (anteriorly) • From the costochondral junction to the margin of the sternum, the muscle layer is replaced by the anterior intercostal membrane ○ Internal intercostal: • Middle layer, fibres pass downwards and backwards from the costal groove • Extends from the margin of the sternum (anteriorly) to the angle of the rib (posteriorly) • From the angle of the rib to the tubercle, the muscle is replaced by the posterior intercostal membrane ○ Innermost layer: • Discontinuous; separated into three parts: 1. Sternocostalis (aka transversus thoracis, anteriorly) 2. Innermost intercostals (laterally: the major part of the inner layer) 3. Subcostalis (posteriorly) Muscle fibres from the anterior (1) and posterior (3) part of this layer cross more than one intercostal space

Question 33

With the aid of a diagram, describe the structure of a spinal nerve from the T2–6 level after it has emerged from the vertebral column. State where it lies in 2the intercostal space (6 marks)

Answer 33

○ 31 pairs of spinal nerves, emerge from the intervertebral foramen (anterior and posterior rami of S1–4 emerge through anterior and posterior sacral foramina respectively) ○ The thoracic intercostal nerves (T2–6) divide into anterior and posterior divisions (rami) ○ The posterior ramus supplies only the muscles of the back (including erector spinae) and overlying skin to a hand’s breadth either side of the midline ○ The anterior ramus passes forwards between the middle and innermost intercostal layers ○ At the angle of the rib, a collateral branch is given off, which runs forwards in the lower part of the space and provides supply to the intercostal muscles, parietal pleura, periosteum and the periphery of the diaphragm (T7–11 only, not T2–6) ○ The main trunk of the nerve continues in the intercostal space and is mostly sensory to skin, giving a lateral cutaneous branch at the midaxillary line and ending as an anterior cutaneous branch at the edge of the sternum

Question 34

Name three procedures in anaesthesia, other than intercostal drain insertion, which make use of the intercostal space (3 marks)

Answer 34

○ Cannula decompression of tension pneumothorax ○ Regional anaesthesia (intercostal nerve and interpleural block) ○ Ultrasound (echocardiography and lung ultrasound in intensive care) **(Non-anaesthesia: pleural aspiration (draining fluid/air, sampling fluid), thoracotomy, lung biopsy)

Question 35

Which nerve root contributes to the lumbar plexus, in what muscle is it formed and where is the muscle found? (4 marks)

Answer 35

○ From the anterior rami of L1–4 (sometimes with a contribution from T12) ○ It is formed within the substance of psoas major muscle (posterior third) • Psoas major lies between the 12th rib and iliac crest on the posterior abdominal wall, anterior to the lumbar transverse processes, and lateral to the lumbar vertebral bodies/intervertebral discs and foramina

Question 36

Name the branches of the lumbar plexus and their respective root

Answer 36

○ Iliohypogastric nerve (L1 +/T12) ○ Ilioinguinal* (L1) ○ Genitofemoral (L1–2) ○ Lateral cutaneous nerve of the thigh (L2–3) ○ Obturator nerve** (L2–4) ○ Femoral nerve (L2–4)

Question 37

Name indications and contraindications for a lumbar plexus block (5 marks)

Answer 37

○ Indications: • Analgesia of the ipsilateral lower limb (hip, femur, knee) ○ Absolute contraindications: • Patient refusal • Local anaesthetic allergy • Local sepsis/infection (puncture site or within psoas compartment) • Coagulopathy ○ Relative contraindications: • Systemic sepsis (particularly for catheter placement) • Fixed cardiac output (due to the risk of epidural/subarachnoid spread)

Question 38

What complications of regional anaesthesia are pertinent to lumbar plexus blockade? (5 marks)

Answer 38

From needle: • Direct trauma to nerves of the lumbar plexus/intraneural injection • Dural puncture • Trauma to retroperitoneal structures/abdominal viscera (e.g. kidney, ureteric injury) • Retroperitoneal haematoma • Psoas abscess From incorrect placement of local anaesthetic: • Epidural/intrathecal spread of local anaesthetic From local anaesthetic: • Hypotension • Intravascular injection/local anaesthetic systemic toxicity (psoas compartment is highly vascular and muscle tissue demonstrates rapid drug absorption)

Question 39

Describe the neurovascular supply of the oesophagus (9 marks)

Answer 39

Nerve supply: • Motor: CN 10*, recurrent laryngeal branches for upper third and vagal plexi for rest • Sensory: pain fibres run with both parasympathetic (CN 10) and sympathetic fibres** (T2–6, from the middle and lower cervical ganglia) • Secretomotor: CN 10 Arterial supply: • Cervical portion: oesophageal branches of inferior thyroid artery (arise from the thyrocervical trunk– third branch of the first part of the subclavian artery***) • Thoracic portion: oesophageal branches of thoracic aorta • Abdominal portion: oesophageal branches of left gastric artery (from the celiac trunk) Venous drainage via oesophageal veins to: • Cervical portion: inferior thyroid vein (draining to brachiocephalic vein; systemic) • Thoracic portion: azygos vein (draining to SVC; systemic) • Abdominal portion: oesophageal tributaries of left gastric vein (draining to portal vein) *Vagal fibres from the nucleus ambiguus supply upper third striated muscle of the oesophagus, fibres from dorsal motor nucleus for lower visceral muscle **This explains the referred pain of oesophagitis– retrosternal dermatomes T2–6 ***In 25%, arises directly from the third part of the subclavian artery

Question 40

List the relations of the thoracic oesophagus (4 marks)

Answer 40

○ Anterior: trachea, left main bronchus, pericardium/left atrium, (left) recurrent laryngeal nerve, anterior vagal trunk ○ Posterior: vertebral bodies, thoracic duct (crossing to the left at T5), descending thoracic aorta, connections to (accessory)/hemiazygos vein, posterior vagal trunk ○ Right: pleura, azygos vein**** ○ Left: pleura, arch of aorta****, thoracic duct (above T5) ****The blue arch is right, the red arch is left

Question 41

What anaesthetic monitoring devices are placed in the oesophagus and what do they measure? (3 marks)

Answer 41

○ Oesophageal Doppler (cardiac output) ○ Transoesophageal echocardiography probe (cardiac structure and function, fluid filling) ○ Oesophageal temperature probe (core temperature) ○ Oesophageal contractility (depth of anaesthesia)

Question 42

Whatfeatures,ofthe distaloesophagus and surrounding structures, form the ‘physiological sphincter’ of the lower oesophagus to reduce reflux of gastric contents? (4 marks)

Answer 42

○ Tonic contraction of circular smooth muscle in the lower oesophagus ○ Fibres of the right crus of the diaphragm surround the lower oesophagus ○ Longitudinal folds of oesophageal mucosa occluding the central lumen ○ The oesophagus enters the stomach at an acute angle ○ The terminal 2–3 cm of the oesophagus are below the diaphragm (raised intraabdominal pressure compresses the oesophagus causing a flap-valve effect) N.B. Gravity is also a contributing factor when upright– hence why patients may experience gastro-oesophageal reflux disease predominantly when lying down

Question 43

Describe the anatomy of the pituitary gland and its relations (8 marks)

Answer 43

○ An endocrine gland at the base of the brain, composed of a (larger) anterior lobe an (smaller) posterior lobe, separated by a pars intermedia ○ Located in the pituitary fossa (or sella turcica – the ‘Turkish saddle’), a depression in the sphenoid bone and the central portion of the middle cranial fossa ○ The roof of the sella turcica is formed by a fold dura (the diaphragma sellae); a small perforation allows the pituitary stalk to pass through in continuity with the hypothalamus (above) and posterior pituitary (below) Relations: ○ Lateral: cavernous sinus, containing the internal carotid artery and CN 6 (with CN 3, CN 4, CN 5.1 and 5.2 lying in the lateral wall of the cavernous sinus) Superior: optic chiasma (anteriorly), hypothalamus and, above that, the third ventricle ○ Anterior/inferior: sphenoidal air sinus Posterior: midbrain and pons

Question 44

What is the hypothalamo-hypophyseal portal venous system? (2 marks)

Answer 44

○ Microcirculation connecting the hypothalamus with the pituitary to expedite transport and exchange of hormones between the hypothalamus and anterior pituitary ○ Blood from the superior hypophyseal (pituitary) arteries supplies the hypothalamus where they form a primary capillary plexus receiving the hypothalamic hormones ○ Blood then drains (by hypophyseal portal veins) to a secondary plexus in the anterior pituitary, where the hypothalamic hormones affect their target cells (in the anteriorpituitary) ○ These capillaries are highly permeable to facilitate the exchange of these hormones

Question 45

What feature a of acromegaly are relevant to the conduct of general anaesthesia?(5marks)

Answer 45

Airway: ° Up to 70% have obstructive sleep apnoea (OSA) due to generalised hypertrophy/ oedema of upper airway mucosa ° This, combined with development of macrognathia and macroglossia can make bag-mask ventilation and intubation more difficult ○ Respiratory: ° Proximal muscle weakness and potential OSA increase risk of postoperative respiratory failure ○ Cardiac: ° Hypertension and left ventricular hypertrophy (LVH) lead to increased risk of cardiac ischaemia and failure ○ Endocrine: ° Multiple endocrine abnormalities can occur, in particular diabetes mellitus, hyper-/hypothyroidism and adrenal insufficiency ○ Other: ° Venous cannulation may be difficult due to excess soft tissue

Question 46

What is the transsphenoidal approach to the pituitary gland? Name the main advantages and complications (5 marks)

Answer 46

Transsphenoidal approach: ○ Elevate the mucosa from the posterior nasal septum (requires fracture/removal of the anterior bony septum, the posterior part is removed but preserved for closure) ○ Through this opening enter the sphenoidal air sinus and, from here, enter the pituitary fossa Complications: °Haemorrhage °Cranial nerve injury (in particular visual deficit) °Persistent CSF leak °Hormonal (panhypopituitarism or transient DI) °Ischaemic stroke (due to vasospasm)

Question 47

What are the indications for a popliteal fossa block? (3 marks)

Answer 47

Surgical procedures below the knee: Foot/ankle surgery (corrective, debridement/amputation, Achilles tendon repair) Interventional radiology to revascularise lower limb below the knee Other: sural nerve biopsy, short saphenous vein (SSV) stripping (Rescue) analgesia for leg/ankle/foot pain (e.g. trauma or postoperative)

Question 48

Describe the anatomy of the popliteal fossa (5 marks)

Answer 48

Boundaries: °Superomedial: the ‘semi’ muscles (semimembranosus and semitendinosus) °Superolateral: medial border of biceps femoris °Inferomedial: gastrocnemius (medial head) °Inferolateral: gastrocnemius (lateral head) °Roof: fascia lata °Floor (proximal to distal): popliteal surface of femur, capsule of knee joint, popliteus Contents (superficial to deep): °Short saphenous vein (pierces roof of popliteal fossa and drains into popliteal vein) °Tibial and common peroneal nerves* °Popliteal vein °Popliteal artery °Popliteal lymph nodes and fat pack the rest of the fossa *The terminal branches of the sciatic nerve – the bifurcation is typically at the apex of the popliteal fossa, but it can occur as far4 proximally as the gluteal region

Question 49

Describe the cutaneous innervation of the sciatic nerve below the knee (6 marks)

Answer 49

Tibial (L4–S3): °Lower half of lateral calf and lateral border of foot, including little toe (sural nerve) °Plantar surface of foot (medial and lateral plantar nerves) °Heel (medial calcaneal branches) Common peroneal/fibular (L4–S2): °Upper half of lateral calf (lateral cutaneous nerve of calf ) °Lower anterolateral calf and dorsum of foot (superficial peroneal nerve) °First web space (deep peroneal nerve) (N.B. Also contributes to the sural nerve via a communicating branch)

Question 50

Describe the cutaneous innervation of the sciatic nerve below the knee (6 marks)

Answer 50

Tibial (L4–S3): • Lower half of lateral calf and lateral border of foot, including little toe (sural nerve) • Plantar surface of foot (medial and lateral plantar nerves) • Heel (medial calcaneal branches) Common peroneal/fibular (L4–S2): • Upper half of lateral calf (lateral cutaneous nerve of calf ) • Lower anterolateral calf and dorsum of foot (superficial peroneal nerve) • First web space (deep peroneal nerve) (N.B. Also contributes to the sural nerve via a communicating branch)

Question 51

Describe a technique for performing a popliteal fossa block (6 marks)

Answer 51

Consent Stop before you block: confirm side and site** SLIMRAG: °Sterile procedure (wash hands, sterile gloves, sterile dressing pack) °Light source/ultrasound °IV access °Monitoring (AAGBI minimum standard) °Resuscitation drugs/equipment available °Assistant (who is happy to assist with regional or general anaesthetic) °General anaesthetic: ensure equipment/drugs available to convert if required °Position: supine (flex knee to 30°) or lateral (block limb uppermost), occasionally prone ● Locate skin crease at popliteal fossa and clean skin of distal lateral thigh with 0.5% chlorhexidine (allow to dry) ● High-frequency linear array ultrasound probe with sterile cover and gel to identify sciatic nerve bifurcation (typically 5–10 cm proximal to the popliteal skin crease) ● In-plane technique, 80–100 mm short bevel regional block needle ● Apply local anaesthetic to skin then insert from lateral side (anterior to tendon of biceps femoris) ● After negative aspiration, slowly inject 15–20 ml of local anaesthetic, aiming for perineurial deposition of local anaesthetic around the division of the sciatic nerve, confirming negative aspiration after every 5-ml injection **Particularly important as the patient is often turned either lateral or prone to perform theblock, increasing risk of wrong site block Block tips... A peripheral nerve stimulator may be used to guide nerve localisation; however, the sciatic nerve contains sensory nerve fibres at this level – this may lead to false negative results if relying on eliciting a motor response The popliteal vein is easily compressed by pressure from the ultrasound transducer, andcare must be taken to ensure that the vein has not been cannulated – this is achieved byvisualising the needle tip, negative aspiration, 5-ml aliquots of local anaesthetic, visualisation of local anaesthetic spread and monitoring the patient for signs of local anaesthetic toxicity

Question 52

Briefly describe the anatomy of the trachea (6 marks)

Answer 52

° Begins as a continuation of the larynx below the cricoid cartilage (C6 level) > 10–12 cm in length (half cervical, half thoracic), 2.5 cm diameter °Terminates at the plane of the sternal angle (T4/5 IV disc) at mid-inspiration (but varies with phase of respiration – more inferior in inspiration and superior in expiration) °Structure maintained by 15–20 C-shaped rings of hyaline cartilage, joined by fibro-elastic tissue ° Posteriorly, trachealis (smooth muscle) joins the ends of the cartilages ° Lined by pseudostratified, columnar epithelium (containing goblet cells) ° Blood supply/venous drainage: inferior thyroid artery and bronchial arteries, drains to inferior thyroid veins °Nerve supply: recurrent branches of vagus nerve supply mucosa (including pain fibres), upper ganglia of sympathetic trunks supply smooth muscle and blood vessels (vasomotor)

Question 53

List relations of the trachea in the neck (C6) and thorax (T4) (8 marks)

Answer 53

Neck: °Anteriorly: anterior jugular veins, sternohyoid, sternothyroid, isthmus of thyroid gland (overlying second–fourth tracheal cartilages), inferior thyroid veins, thyroid ima artery °Laterally: lobes of the thyroid gland, carotid sheath (common carotid artery, internal jugular vein, vagus nerve) Posteriorly: oesophagus, recurrent laryngeal nerves (in tracheo-oesophageal grove) Thorax: °Anteriorly: left brachycephalic vein, brachiocephalic trunk, left common carotid artery, arch of aorta, thymus °Left: arch of aorta (‘red arch’), left common carotid artery, left subclavian artery, left recurrent laryngeal nerve, pleura °Right: azygos vein (‘blue arch’), right CN 10, pleura °Posteriorly: oesophagus, left recurrent laryngeal nerve

Question 54

List immediate/early and late complications of a tracheostomy placed between the second and third tracheal rings (6 marks)

Answer 54

Immediate/early: - From instrumentation: bleeding, tracheal cartilage fracture, posterior tracheal wall/ oesophageal injury, pneumothorax, laryngeal nerve damage - From loss of airway: hypoxia, false passage, surgical emphysema Late: - From instrumentation: bleeding, infection - From loss of airway: hypoxia, displacement, blockage - From scarring: tracheal stenosis, tracheo-oesophageal fistula, trachea granuloma, vocal changes, persistent stoma, dysphagia, disfiguring scar, tracheomalacia

Question 55

Name the nerves labelled A–E. Describe their area of cutaneous innervation (10 marks)

Answer 55

A) Tibial* °Lies posterior to the medial malleolus, typically posterior to the posterior tibial artery** °Gives medial calcaneal branches, which pierce flexor retinaculum to supply the skin of the heel (including weight-bearing surface) °Divides into the medial and lateral plantar nerves in the foot (under flexor retinaculum), which provide cutaneous innervation to the sole of the foot (medial 3½ toes and lateral 1½ toes respectively)*** Also supplies skin over distal phalanges B) Saphenous °Largest sensory branch of the femoral nerve °Below the knee it travels with the great/long saphenous vein °Sensation to medial calf and medial aspect of the ankle/foot (as far as first MTPJ –‘bunion area’) C) Sural °Formed by the union of branches of the tibial and common peroneal nerves °Below the knee it travels with the small/short saphenous vein •Passes posterior to the lateral malleolus (cf. saphenous nerve and GSV lie anterior to the medial malleolus) ° Innervation to the lateral aspect of the calf, ankle and foot (including little toe) D) Deep peroneal/fibular °Common peroneal divides into superficial and deep branches within peroneus longus °Deep nerve provides sensory supply to 1st web space E) Superficial peroneal/fibular Pierces deep fascia in the distal third (between middle and distal thirds) of the leg (emerges between extensor digitorum longus and peroneus brevis) °Sensation to lower half of anterolateral leg and ankle, dorsum of the foot via medial and lateral branches *There is no posterior tibial nerve! (This terminology has been replaced, it is now simply the tibial nerve, but is still seen in clinical texts) **Mnemonic for the structures behind the medial malleolus (from anterior to posterior): ‘Tom, Dick And Very Naughty Harry’ Tibialis posterior, FDL, posterior tibial Artery and Vein, tibial Nerve, FHL ***Aide-memoire for distribution of plantar nerves: medial plantar (like median nerve on palm of the hand), lateral plantar (like ulnar nerve)

Question 56

b) Identify structures F–I (4 marks

Answer 56

F) Achilles tendon G) Dorsalis pedis artery H) (Inferior) extensor retinaculum I) Small/short saphenous vein

Question 57

Which of these nerves lie superficial to deep fascia at the level blocked? (3 marks)

Answer 57

○ Saphenous ○ Superficial peroneal/ ○ fibular ○ Sural

Question 58

(Ankle block) From time of injection to onset of block, which of these nerves classically takes the longest and why? Why is it the only nerve for which a nerve stimulator would be useful? (3 marks)

Answer 58

○ Tibial takes the longest as it is the largest nerve ○ It is the only nerve in this block with a motor component (saphenous, deep peroneal/fibular, superficial peroneal/fibular and sural are sensory branches at this level)

Question 59

From the image, name structures 1–5 and the nerves that pass through them (10 marks)

Answer 59

1) Cribriform plate of ethmoid bone (CN 1) 2) Optic canal (CN 2) 3) Foramen rotundum (CN 5.2/maxillary division) 4) Foramen ovale (CN 5.3/mandibular division, lesser petrosal nerve from CN 9) 5) Internal auditory/acoustic meatus (CN 7 including nervus intermedius, CN 8)

Question 60

Name the landmarks labelled A–C and the venous sinus associated with them (3 marks)

Answer 60

A) Groove for transverse sinus (transverse venous sinus) B) Groove for sigmoid sinus (sigmoid venous sinus) C) Internal occipital protuberance (confluence of sinuses)

Question 61

Ontheimage, demonstrate the boundaries of the anterior, middle and posterior cranial fossae. Describe the principal part and function of the brain associated with each (3 marks)

Answer 61

○ Anterior cranial fossa (frontal lobe): emotion/personality/behaviour, primary motorcortex ○ Middle cranial fossa (temporal lobe): auditory processing, memory and language ○ Posterior cranial fossa (cerebellum): coordinates and regulates voluntary movement (integrates sensory input from spinal cord to motor control for coordination and precision)

Question 62

What is the name of the region indicated by D? What clinical condition is associated with trauma in this territory and why? What are the clinical features? (4 marks)

Answer 62

○ Pterion – a region on the lateral side of the skull where the plate of bone is thin (see surface marking on illustration) ○ Trauma here is associated with extradural haematoma because the anterior division of the middle meningeal artery lies on the deep surface, which can be damaged if the overlying bone is fractured Clinical features: • Initial lucid interval after trauma • Subsequent rising ICP with headache, vomiting, confusion, deteriorating consciousness and seizures CN 3 palsy (ipsilateral dilated pupil in ‘down and out’ position)* • Contralateral homonymous hemianopia • Contralateral hemiparesis/brisk reflexes and subsequent features of brain herniation *CN 3 palsy begins with a dilated (‘blown’) pupil and then adopts the ‘down and out’ position – the parasympathetic nerve fibres travel on the outside of the nerve and so are affected first by compression on the tentorium cerebelli, before the motor fibres are then compromised

Question 63

Identify structures A–E in these cadaveric images (5 marks)

Answer 63

A) Axillary artery B) Radial artery C) Brachial artery D) Deep palmar arch E) Superficial palmar arc

Question 64

Name the artery running with the following nerve (3 marks): Radial nerve (in the proximal arm) Median nerve (in the cubital fossa) Ulnar nerve (at the wrist)

Answer 64

Radial nerve in the proximal arm: profunda brachii artery Median nerve in the cubital fossa: brachial artery Ulnar nerve at the wrist: ulnar artery

Question 65

Describe collateral arterial supply of hand (8 marks)

Answer 65

○ Supplied from radial and ulnar arteries (arise from the brachial artery at the level of the neck of the radius, in the cubital fossa) ○ They enter the hand to form two arterial arches: superficial (principally from the ulnar) and deep (principally from the radial) Radial artery: ○ Palpable at the wrist, then continues through the anatomical snuff box as the ‘deep branch’ to form the deep palmar arch (which is completed by the deep branch of the ulnar artery) ○ Gives a superficial branch 2 cm proximal to the wrist crease (passes over the flexor retinaculum, through the thenar muscles and contributes to the superficial arch) Ulnar artery: ○ Palpable at the wrist, then continues over the flexor retinaculum (in canal of Guyon) to form the superficial palmar arch (completed by the superficial branch of the radial artery) ○ Gives a deep branch (through the hypothenar muscles), which contributes to the deep arch Palmar arches: ○ Superficial: supplies medial 3½ digits via palmar digital arteries (cf. opposite to the ulnar nerve distribution, which provides sensory supply to the medial 1½ digits) ○ Deep: supplies the lateral 1½ digits via princeps policis and radialis indicis arteries (cf. median nerve provides sensory supply to the lateral 3½ digits) ○ The two arches are also linked by metacarpal arteries

Question 66

What is Allen’s test? (4 marks)

Answer 66

Used before attempting cannulation of the radial artery Test to assess adequate ulnar collateral supply to the hand Compress radial and ulnar arteries at the wrist Elevate hand and make a fist for 30 seconds When opening the hand and the hand is pale (due to limited arterial supply) Release the ulnar artery: colour should return to the hand within 10 seconds Poor ulnar arterial supply is indicated if this is prolonged (The accuracy of this test is questioned)

Question 67

Name structures A–E on this image of the brachial plexus (5 marks)

Answer 67

A) C6 nerve root B) Superior trunk C) Lateral cord D) Lateral pectoral nerve E) Medial cutaneous nerve of the arm

Question 68

Name the nerve roots that contribute to the nerves labelled F–I (4 marks)

Answer 68

F) Ulnar nerve: C8–T1 (sometimes C7) G) Radial nerve: C5–T1 H) Median nerve: C5–T1 I) Axillary nerve: C5–6

Question 69

What motor response is demonstrated on stimulation of the lateral, posterior and medial cords of the brachial plexus? (3 marks)

Answer 69

Posterior cord: wrist/finger extension Medial cord: thumb adduction, wrist flexion Lateral cord: elbow flexion, forearm supination

Question 70

Name the part(s) of the brachial plexus targeted by the following blocks (4 marks): interscalene supraclavicular infraclavicular axillary

Answer 70

Interscalene: roots Supraclavicular: distal trunks/proximal divisions Infraclavicular: cords Axillary: branches (peripheral nerves)

Question 71

What are the benefits of ultrasound-guided (over anatomical landmark or nerve stimulator) brachial plexus blocks? (4 marks)

Answer 71

Allows continuous visualisation of needle tip/placement and local anaesthetic spread Quicker procedure Faster onset Longer duration Higher success rate Reduced local anaesthetic volume used Avoidance of discomfort of nerve stimulation (especially if supplying an injury/ fractured limb) Allows for anatomical variation and differing needle approach Reduced incidence of intravascular injection Reduced incidence of pneumothorax (No difference in incidence of nerve injury demonstrated in current evidence)

Question 72

On the image, name structures A–E (5 marks)

Answer 72

A) Vertebral artery B) Basilar artery C) Posterior communicating artery D) Anterior cerebral artery E) Internal carotid artery

Question 73

What is the origin of A and E? (2 marks)

Answer 73

A) Subclavian artery (first branch of the first part) E) Common carotid artery (level with the superior border of thyroid cartilage – at C4)* *Note that the common carotid artery arises from the brachiocephalic trunk on the right, and directly from the arch of the aorta on the left

Question 74

Where are the common locations of intracranial vascular aneurysms and with what frequencies do they occur? (6 marks)

Answer 74

Anterior communicating (40%) Posterior communicating (30%) Middle cerebral artery (20%)

Question 75

What is the significance of the circle of Willis? (1 mark)

Answer 75

Provides collateral circulation for the brain, compensating for reduced flow through individual segments of the arterial circle and thus maintaining blood supply to the brain

Question 76

Describe the speech deficit that occurs from occlusion of the: i) dominant hemisphere middle cerebral artery anterior branch ii) dominant hemisphere middle cerebral artery posterior branch iii) dominant hemisphere middle cerebral artery (3 marks)

Answer 76

i) expressive dysphasia (anterior speech area of Broca) ii) receptive dysphasia (posterior speech area of Wernicke) iii) global aphasia

Question 77

Which artery has been affected in a patient suffering from an occlusive stroke presenting with: i) 6 motor/sensory deficit of the contralateral lower limb ii) contralateral homonymous hemianopia with macular sparing iii) motor/sensory deficit of the contralateral upper limb and face (3 marks)

Answer 77

i) ACA ii) PCA** iii) MCA

Question 78

Name the nerve labelled A on the image (1 mark)

Answer 78

CN 10 (vagus nerve)

Question 79

From which nuclei does it arise? Structure A (4 marks)

Answer 79

○ Dorsal nucleus of vagus (parasympathetic: heart, lungs, gut) ○ Nucleus ambiguus (motor: skeletal muscle of palate, larynx, pharynx) ○ Nucleus of tractus solitarius (special sense: taste from epiglottis, cardiorespiratory andvomiting reflexes) ○ Sensory nuclei of trigeminal (general sense: larynx/pharynx, dura of posterior cranial fossa, ear*) *CN 10 supply to ear: lower half of outer surface of tympanic membrane, external auditory meatus and small area behind auricle

Question 80

What is the name of this foramen (B) in the base of the skull? (1 mark)

Answer 80

Jugular foramen

Question 81

Which structures pass through it? Foramen b (4 marks)

Answer 81

Anterior compartment: Inferior petrosal sinus CN 9 Middle compartment: CN 10 and 11 Posterior compartment: Sigmoid sinus (becoming continuous with IJV)

Question 82

What is structure C (a branch of A)? To which vascular structure is it most closely related on the left and on the right? (4 marks)

Answer 82

Left recurrent laryngeal nerve Left: arch of aorta Right: subclavian artery

Question 83

What stimuli can increase the outflow of the nerve labelled A, and what effects are seen during anaesthesia? (6 marks)

Answer 83

Effects: ○ Bradycardia, asystole in severe circumstances ○ Laryngospasm (Brewer–Luckhardt reflex: laryngospasm provoked by distant stimuli) ○ Bronchospasm Stimuli: ○ Dura (e.g. subarachnoid haemorrhage) ○ Zygoma (e.g. surgery, trauma) ○ Extraocular muscles, particularly medial rectus (e.g. eye surgery) ○ Carotid sinus (e.g. carotid sinus massage) ○ Pharynx and glottis (e.g. intubation of child when hooking epiglottis) ○ Bronchial tree ○ Heart ○ Mesentery and peritoneum (e.g. insufflation during laparoscopy) ○ Bladder and urethra ○ Testis, uterus and cervix (e.g. exteriorising uterus, gynaecological surgery, PV bleed) ○ Rectum and anus (e.g. anal stretch)

Question 84

Name structures A–D on these images of the heart (4 marks)

Answer 84

A) Left coronary artery B) Anterior interventricular/left anterior descending artery C) Right (acute) marginal artery D) Posterior interventricular/descending artery

Question 85

Name structures E–H (4 marks)From where do the main coronary arteries arise? (2 marks)

Answer 85

E) Coronary sinus F) Great cardiac vein G) Middle cardiac vein H) Small cardiac vein

Question 86

What proportion of the cardiac output is supplied to the myocardium

Answer 86

5% or 250 ml/minute (can increase fivefold during exercise)

Question 87

What is meant by coronary arterial dominance? (1 mark)

Answer 87

This is defined by the vessel that gives rise to the posterior interventricular artery (usually RCA), as this in turn gives rise to the AV nodal artery

Question 88

Which artery supplies the AV node and where does it arise from? (2 marks)

Answer 88

> AV nodal artery > In >80% it is from the RCA, in 10% it is a continuation of the circumflex branch of the LCA <10% have a ‘balanced’ circulation where the AV node is supplied by both the RCA and circumflex (LCA): branches of both sides run in or near the posterior interventricular groove

Question 89

Which artery supplies the SA node and where does it arise from? (2 marks

Answer 89

SA nodal artery In 60% it arises from the RCA, in 40% from the circumflex artery (LCA)

Question 90

What are the ECG features of right coronary artery occlusion? (2 marks)

Answer 90

> Inferior MI: features in leads II, III and aVF - ST segmental elevation (subsequent development of Q waves) (Reciprocal ST depression in aVL +/ V1) - Other features: heart block, right bundle branch block

Question 91

Describe the difference between a type I and type II acute myocardial infarction? (2 marks)

Answer 91

A type I MI describes focal myocardial ischaemia/necrosis resulting from a lesion in specific coronary artery (most commonly rupture of an atheromatous plaque) A type II MI describes myocardial ischaemia/necrosis from an oxygen supply/demand mismatch (e.g. secondary to fast atrial fibrillation/severe tachycardia and hypotension), a coronary abnormality may not be present

Question 92

) On the diagram OSCE8, name structures A, B and C. State at what vertebral level they pass through the diaphragm, and name a structure they travel with at this level (9 marks)

Answer 92

A) Inferior vena cava •Vena caval opening: T8 •Transmits: IVC, right phrenic nerve B) Oesophagus •Oesophageal opening: T10 •Transmits: oesophagus, vagal trunks (anterior and posterior), left gastric vessels, lymphatics from lower third of oesophagus C) Aorta (junction of descending thoracic aorta/abdominal aorta) •Aortic hiatus: T12 •Transmits: aorta, azygos vein (on right of aorta) and thoracic duct (between them) Easy to remember! Vena cava – 8 letters Oesophagus – 10 letters Aortic hiatus – 12 letters

Question 93

b) What is structure D, and what is it derived from? (1 mark)

Answer 93

D) Central tendon* (derived from the septum transversum)

Question 94

At which point does the left phrenic nerve pierce the diaphragm? (1 mark)

Answer 94

Apex beat of the heart (5th ICS on the left, in the midclavicular line)

Question 95

Describe the nerve supply of the diaphragm (3 marks)

Answer 95

Motor supply: phrenic nerves only (C3/4/5**) Sensory supply: • Central part: phrenic nerve (C3/4/5) • Peripheral part: lower six intercostal/thoracoabdominal nerves (T7–12)

Question 96

What is the normal level of the diaphragm in the midclavicular line? (2 marks)

Answer 96

Left hemidiaphragm: 5th intercostal space Right hemidiaphragm: 5th rib

Question 97

What are the potential causes of a raised unilateral or bilateral hemidiaphragm? (4 marks)

Answer 97

Unilateral: ° Phrenic nerve palsy ° Lobar/lung collapse Bilateral: °Poor inspiratory effort ° Restrictive lung disease ° Gastrointestinal obstruction/ileus ° Ascites ° Pregnancy ° Obesity ° Other (e.g. intra-abdominal mass)

Question 98

Name structures A–E on the image OSCE9 (5 marks)

Answer 98

A) Superior sagittal sinus B) Inferior sagittal sinus C) Straight sinus D) Left transverse sinus E) Right sigmoid sinus

Question 99

What drains to and from structure F? (5 marks)

Answer 99

Structure F: cavernous sinus Receives: ° ophthalmic veins (superior and inferior), ° cerebral veins (superficial middle cerebral +/ inferior cerebral), ° sphenoparietal sinus ○ Drains to: petrosal sinuses (superior and inferior) N.B. The intercavernous sinuses (anterior and posterior) communicate between the two cavernous sinuses, and emissary veins connect the cavernous sinus and pterygoid venous plexus below

Question 100

What structures lie within structure F? (5 marks)

Answer 100

Within the sinus: • Internal carotid artery (carrying postganglionic sympathetic fibres of the internal carotid plexus, including those for dilator pupillae and levator palpebrae superioris) • CN 6 (Venous blood) In the lateral wall: • CN 3 • CN 4 • CN 5.1 and 5.2

Question 101

d) What are the clinical features of thrombosis of structure F? (5 marks)

Answer 101

Features of raised ICP: Symptoms: headache, nausea/vomiting, falling level of consciousness, seizures Signs: papilloedema, dropping GCS, CN 3/6 palsy Features related to the cavernous sinus anatomy: CN 3–6 palsies Impaired venous drainage of the eye (proptosis, chemosis and injected eye)

Question 102

Name structures A–F on this image (6 marks)

Answer 102

A) Spermatic cord B) Superficial inguinal ring C) Deep inguinal ring D) Pubic tubercle E) Anterior superior iliac spine F) Inferior epigastric artery

Question 103

On the diagram, identify the areas supplied by the nerves numbered 1–5 (5 marks)

Answer 103

1) Lateral cutaneous branch of intercostal nerve T10 2) Iliohypogastric nerve (T12 and L1) 3) Ilioinguinal nerve (L1) 4) Genitofemoral nerve (femoral branch; L1–2) 5) Lateral cutaneous nerve of thigh (L2–3)

Question 104

What methods of anaesthesia may be employed for inguinal hernia repair? (3 marks

Answer 104

General anaesthesia Spinal anaesthesia (or epidural) Local anaesthesia: Local infiltration Iliohypogastric/ilioinguinal nerve block TAP block Caudal block

Question 105

Describe how you would manage a patient who was having inguinal hernia repair under local anaesthesia infiltration and was beginning to experience discomfort (6 marks)

Answer 105

> Ask the surgeon to stop > Speak to the patient: - Offer reassurance - Confirm the nature of the discomfort (some sort of sensation is expected) - If pain, determine the level of discomfort (mild/moderate/severe) Mild pain: - Further local anaesthesia infiltration - Intravenous opiate analgesia (e.g. fentanyl) - Nitrous oxide or intravenous remifentanil/propofol sedation/analgesia Severe pain: - Confirm with the surgeon the extent of surgery undertaken/still to perform - With a significant proportion of the operation still to perform, consider alternative/additional technique: TAP/nerve block (if the maximal dose of local anaesthetic permits) or spinal/GA (depending on patient suitability and concern over sterility/repositioning) Postoperatively: - Debrief patient and offer apology as appropriate

Question 106

Name structures A–D on the diagram OSCE11 (4 marks)

Answer 106

A) Epiglottis (elastic cartilage) B) Thyroid cartilage (hyaline cartilage) C) Cricoid cartilage (hyaline cartilage) D) Arytenoid cartilages (hyaline cartilage)

Question 107

Names structures E–I (5 marks

Answer 107

E) Thyrohyoid membrane F) Cricothyroid membrane G) Aryepiglottic fold H) Vestibular fold (false cords) I) Cricovocal membrane (upper edges form the true vocal cords)

Question 108

c) Describe the innervation of the larynx (3 marks)

Answer 108

Superior laryngeal nerve: Internal branch (sensation above vocal cords: from dorsum of epiglottis to cords) External branch* (motor supply to cricothyroid) Recurrent laryngeal nerve: Sensation below the vocal cords Motor supply to all intrinsic muscles of the larynx except cricothyroid *Occasionally also supplies the cricopharyngeus part of the interior constrictor of the pharynx

Question 109

d) How might injury to the vagus nerve or its branches affect the larynx? (4 marks)

Answer 109

Superior laryngeal nerve**: reduced vocal cord tension, hoarse voice Recurrent laryngeal nerve: Complete lesion: ipsilateral vocal cord adopts a position midway between abduction/adduction Partial lesion***: ipsilateral vocal cord adopts a midline/adducted position (because adductors are stronger than abductors) **Reduced sensation in the upper larynx also poses an aspiration risk ***Bilateral partial lesions lead to complete airway obstruction as both cords adopt the midline position (Semon’s law)

Question 110

How can you anaesthetise the larynx for an awake fibre-optic intubation? (4 marks)

Answer 110

○ Nebulised lignocaine ○ Topical local anaesthetic using a mucosal atomiser device (nasal mucosa, naso-/oro-/ laryngopharynx) ○ ‘Spray as you go’ (laryngopharynx, larynx, trachea) ○ Translaryngeal approach**** (cricothyroid puncture) is sometimes used ○ Nerve blocks: anterior glossopharyngeal, superior thyroid (rarely used) ○ Cocaine-soaked pledgets (again, rarely used) ○ Coadministration of sedation can reduce local anaesthetic requirement (e.g. TCI propofol or remifentanil) ****Introduces local anaesthetic to the lower airway by inserting a needle through the cricothyroid membrane and injecting – asking the patient to take a deep breath takes the local anaesthetic into the lower airway and often precipitates coughing, which further disperses the anaesthetic around the upper airway

Question 111

Name structures A–E on the image OSCE12 (5 marks)

Answer 111

A) Left lobe of the liver B) Gall bladder C) Groove for inferior vena cava D) Ligamentum teres (or round ligament of liver; obliterated (left) umbilical vein that lies in the free edge of the falciform ligament) E) Fissure for ligamentum venosum

Question 112

Describe the microscopic architecture of the liver (6 marks)

Answer 112

Numerous ways to describe this, based around the portal triad, a hepatic lobule or acinus ○ Portal triads run throughout the liver, which consist of: ° Arteriole (branch of hepatic artery proper) ° Venule (branch of the hepatic portal vein) ° Bile ductule (tributary of the biliary tree bile duct) (And other structures, e.g. lymphatic vessels) Around these lie hepatic lobules: Columnar structure • In cross-section is hexagonal in shape and around 1 mm in diameter • Consists of hepatocytes layered around a central venule (which drains to hepatic vein and then the inferior vena cava) • The edges abut other lobules, the corners converge on a portal triad • The portal triad supplies blood from the gastrointestinal tract, for the processing of absorbed enteric content • Functionally, three zones of metabolic activity are described, centring on the portal triad: ° Zone 1: cells closest to the perimeter of the triad, most metabolically active (greatest availability of oxygen supply from the arterial blood) ° Zone 2: intermediate zone ° Zone 3: least metabolically active, lowest oxygen supply (therefore vulnerable to ischaemia) °Metabolic activity of zones are adapted to their oxygen supply (e.g. β-oxidation of fatty acids in zone 1, glycolysis in zone 3) Zone 3 is most susceptible to ischaemic liver injury

Question 113

Name four sites of portosystemic anastomosis (4 marks)

Answer 113

1) Lower oesophagus (connecting left gastric vein, draining lower third of oesophagus, with the azygos vein, draining middle third) 2) Retroperitoneal veins (drain retroperitoneal surfaces of organs to the body wall veins) 3) Bare area of the liver (drains retroperitoneal surface liver to body wall veins) 4) Periumbilical veins (the ligamentum teres (umbilical vein) can recanalise in portal hypertension, connecting the portal vein with the superior/inferior epigastric veins and anterior abdominal wall veins) 5) Upper anal canal (connects the superior rectal vein (which becomes the inferior mesenteric vein, draining the mid- and hindgut) with the middle and inferior rectal veins (which drain to the inferior pudendal vein and then to the internal iliac vein)) 6) Ductus venosus (can recanalise in portal hypertension, connecting left branch of the portal vein with the inferior vena cava)

Question 114

Name the two vessels connected by a transjugular intrahepatic portosystemic shunt (TIPSS) procedure. How does this help to treat patients with liver cirrhosis? (5 marks)

Answer 114

○ Portal vein and hepatic vein ° In liver cirrhosis, the hepatic scarring causes constriction of the portal venous system, increasing resistance to flow ° Portal hypertension then develops causing the creation of a collateral circulation (portosystemic anastomoses – see above), which is prone to bleeding ○ A TIPSS bypasses the liver, so portal blood drains directly to the systemic veins (reducing pressure in the portal system and therefore the risk/extent of bleeding)

Question 115

Name structures 1–10 on this image of the lateral wall of the nasal cavity (10 marks)

Answer 115

1) Middle turbinate/concha (of ethmoid bone) 2) Opening of frontal sinus 3) Opening of maxillary sinus 4) Opening of nasolacrimal duct 5) Hard palate 6) Soft palate 7) Eustachian tube 8) Sphenoidal air sinus 9) Frontal air sinus 10) Tongue

Question 116

Name the parent nerve from which the nerves labelled in the diagram arise (5 marks)

Answer 116

1. Anterior ethmoidal nerve (nasal branches): continuation of nasociliary branch of ophthalmic division CN 5.1 2. Anterior superior alveolar nerve (nasal branches): maxillary division CN 5.2 3. Nasopalatine nerve: maxillary division CN 5.2 4. Greater and lesser palatine nerves: maxillary division CN 5.2 5. Olfactory nerves: CN 1

Question 117

List the structures/cavities passed through, before reaching the trachea, with the fibre-optic scope when performing a nasal intubation (5 marks)

Answer 117

Anterior nares (nostrils) Nasal cavity Posterior nares (choana) Nasopharynx Oropharynx Laryngopharynx Larynx

Question 118

Name structures A–E on this diagram of the paravertebral space (5 marks)

Answer 118

A) Dorsal ramus of spinal nerve B) Posterior intercostal membrane (from internal intercostal muscle) C) External intercostal muscle D) Parietal pleura E) Transverse process of vertebra

Question 119

Name the contents of the paravertebral space (5 marks

Answer 119

Spinal nerve (ventral/dorsal rami) Intercostal artery Intercostal vein Rami communicantes of sympathetic chain with spinal nerves (white/grey) Paravertebral sympathetic chain Lymphatics Fat

Question 120

Name four complications of paravertebral block (4 marks)

Answer 120

° Nerve injury ° Bilateral block (spread to the contralateral side via the epidural space) ° Epidural spread ° Intrathecal injection ° Hypotension ° Horner’s syndrome ° Pneumothorax/lung injury (in thoracic region) ° Damage to abdominal retroperitoneal viscera, e.g. liver, kidney (in lumbar region) ° Vascular puncture: intravascular injection and local anaesthetic systemic toxicity, bleeding

Question 121

Describe a technique for performing a paravertebral block (6 marks)

Answer 121

○ Consent ○ Stop before you block: confirm side and site SLIMRAG: • Sterile procedure (wash hands, sterile gloves, sterile dressing pack) • Light source/ultrasound • IV access • Monitoring (AAGBI minimum standard) • Resuscitation drugs/equipment available • Assistant (who is happy to assist with regional or general anaesthetic) • General anaesthetic (ensure equipment/drugs available to convert if required) • Position: either lying on side or sitting • Clean the skin with 0.5% chlorhexidine (allow to dry) • High-frequency linear/curvilinear array ultrasound probe with sterile cover and gel: - Identify the vertebral spinous process - Move laterally to the transverse process and costotransverse joint - Then angle obliquely to identify the superior costotransverse ligament (hyperechoic) - In-plane technique, 18 G Touhy needle - Insert needle to make contact with the transverse process, then walk off it caudally (or cranially) to a level 10 mm deeper (may notice a slight loss of resistance) - After negative aspiration, slowly inject up to 20 ml of local anaesthetic (less if a multi- level approach is used)

Question 122

Name the nerves that provide cutaneous innervation of the areas A–E in the diagram. Which one does not originate from the brachial plexus*? (6 marks

Answer 122

A) Lateral cutaneous nerve of the forearm (continuation of the musculocutaneous nerve) B) *Intercostobrachial nerve (the lateral cutaneous branch of T2 – not part of the brachial plexus) C) Median nerve D) Medial cutaneous nerve of the forearm E) Axillary nerve

Question 123

Name two cutaneous branches of the radial nerve in the upper limb (2 marks)

Answer 123

Posterior cutaneous nerve of the arm Inferior/lower lateral cutaneous nerve of the arm Posterior cutaneous nerve of the forearm Superficial branch of the radial nerve (terminal continuation of the radial nerve)

Question 124

c) Name three nerves with cutaneous innervation that may be blocked in the forearm? (3 marks)

Answer 124

○ Median nerve (easiest to block in midforearm, lying between flexor digitorum superficialis and flexor digitorum profundus) ○ Radial nerve (superficial branch; most easily blocked just as it enters the forearm at the lateral aspect of the elbow/cubital fossa, lying between brachioradialis and brachial muscles) ○ Lateral cutaneous nerve of the forearm (continuation of the musculocutaneous nerve at the lateral border of the biceps tendon, runs with the cephalic vein) ○ Ulnar nerve (runs under flexor carpi ulnaris and approaches ulnar artery) ○ Medial cutaneous nerve of the forearm (less easy/reliable to identify, runs with the basilic vein)

Question 125

Name the muscle that overlies each of the following nerves in the midforearm (3 marks)

Answer 125

○ Median nerve: flexor digitorum superficialis ○ Ulnar nerve: flexor carpi ulnaris (Superficial branch of ) ○ radial nerve: brachioradialis

Question 126

Name the muscle in OSCE16, and describe its origin and insertion (3 marks)

Answer 126

○ Rectus abdominis muscle • Origin: pubic crest (lateral head) and pubic symphysis (medial head) • Insertion: anterior surface of 5th, 6th and 7th costal cartilages

Question 127

At what level are the tendinous intersections (which give this muscle its classical appearance), and to which layer of the rectus sheath are they adherent? (2 marks)

Answer 127

Upper: at the level of the xiphoid process Middle: midway between xiphoid process and umbilicus Lower: at the level of the umbilicus Adherent to anterior layer of sheath (visible through skin of lean individuals – ‘6 pack’)

Question 128

Describe the layers and contents of the rectus sheath (6 marks)

Answer 128

Layers (in relation to rectus abdominis): ○ Above costal margin: • Anterior: aponeurosis of external oblique only • Posterior: ribs/costal cartilages only (no sheath) ○ Costal margin to arcuate line: • Anterior: aponeuroses of internal oblique (anterior lamella) and external oblique • Posterior: aponeuroses of internal oblique (posterior lamella) and transversus abdominis ○ Below arcuate line (around halfway between umbilicus and pubic symphysis): • Anterior: aponeuroses of all three muscles • Posterior: transversalis fascia (no sheath) Contents: Rectus abdominis muscle (and pyramidalis muscle when present – around 80%) Superior and inferior (deep) epigastric arteries, with their accompanying veins T7–11 thoracoabdominal and T12 (subcostal) nerves, with their accompanying vessels (motor to rectus abdominis; sensory to parietal peritoneum, muscle and overlying skin)

Question 129

Describe the regions of the following dermatomes (3 marks) • T10 • L1 • T7

Answer 129

T10: umbilicus L1: inguinal ligament T7: xiphoid process Block tips... If inserting a rectus sheath catheter, an 18 G Tuohy needle provides excellent ultrasound visibility and allows passage of an appropriately sized catheter

Question 130

Describe how you would perform a rectus sheath block (6 marks)

Answer 130

Consent Stop before you block: confirm side and site (usually bilateral) SLIMRAG: Sterile procedure (wash hands, sterile gloves, sterile dressing pack) Light source/ultrasound IV access Monitoring (AAGBI minimum standard) Resuscitation drugs/equipment available Assistant (who is happy to assist with regional or general anaesthetic) General anaesthetic: ensure equipment/drugs available to convert if required Position the patient supine, exposed from costal margin to inguinal ligament Clean the field with 0.5% chlorhexidine (allow to dry) High-frequency linear array ultrasound probe with sterile cover and gel Place the probe in the midline (midway between the xiphisternum and umbilicus), aligned transversely, then scan laterally: Off the midline is the oval appearance of the rectus abdominis muscle Two echogenic layers on posterior surface: posterior rectus sheath and peritoneum (with intervening transversalis fascia appearing dark) In-plane technique, 80-mm short-bevel regional block needle: inserted from lateral to medial, aiming for the needle tip to reach the potential space between the muscle and posterior wall of the rectus sheath After negative aspiration, slowly inject 20–30 ml local anaesthetic on either side (depending on dose calculation), confirming negative aspiration after every 5-ml injection

Question 131

What is meant by the term true, false and floating ribs? (6 marks)

Answer 131

Relates to the anterior attachment of the rib/costal cartilage: True ribs (1–7): Attach/articulate directly with the sternum/manubrium False ribs (8–10): Articulate with the rib/costal cartilage immediately above (i.e. indirectly with the sternum)Floating ribs (11–12): No anterior attachment (anterior end lies free in the body wall musculature)

Question 132

Identify the bone shown in OSCE17, and describe two ways of determining which side of the body it is from (3 marks)

Answer 132

> First rib How to ‘side’ the bone: > Scalene tubercle present on the superior surface of the shaft (for attachment of scalenus anterior) > In the correct orientation, the rib should lie stable on a flat surface with each end touching the table, and the tubercle will be the most superior structure (and lies posteriorly)

Question 133

Describe five features of the first rib that are different from/not seen on a typical rib (5 marks)

Answer 133

○ Singular articular surface on the head of the rib as atypical ribs (1, 11 and 12) articulate posteriorly with a single vertebra from its own level (i.e. rib 1 and T1) – typical ribs have two facets ○ Angle and tubercle of first rib are combined (typical ribs have separate angle and tubercle) ○ Flattened from top to bottom creating superior/inferior surfaces and medial/lateral borders (typical ribs are flattened from side to side, forming inner and outer surfaces with a smooth upper and sharp lower border) ○ Scalene tubercle present on the superior surface (not present on other ribs) ○ Grooves for the subclavian vein and artery/lower trunk of the brachial plexus (anterior and posterior to the scalene tubercle respectively) ○ Costal groove absent from under surface (present on typical ribs) ○ The anterior end forms a primary cartilaginous joint with the manubrium (this type of joint is called a synchondrosis (i.e. two bones with intervening hyaline cartilage),which only allows limited movement, thus providing a brace for the ribs below to ‘pull up’ against via the intercostal muscles*) *Typical ribs articulate anteriorly with the sternum/rib above through synovial joints to allow movement during respiration

Question 134

Describe the movements that bring about spontaneous (‘negative pressure’) ventila- tion (6 marks)

Answer 134

There are three ‘diameters’ to the thorax: anteroposterior, transverse and vertical ○ During inspiration these diameters increase, and lung volume expands (the lungs being held to the inside of the thoracic cage by the negative pressure in the pleural potential space) ○ This expansion is accompanied by a drop in pressure within the airspaces of the lungs, so air enters (the reverse holds true for expiration) These changes are thus: °Anteroposterior diameter: increased by the ‘pump handle’ movement, which raises the anterior end of the ribs (upper six ribs/most marked in ribs 2–6, axis ofmovement along neck of rib) °Transverse diameter: increased by the ‘bucket handle’ movement, which raises the middle part of the ribs (lower six ribs/most marked in ribs 7–10, axis of movement ribs between the anterior/posterior ends of each rib) °Vertical diameter: descent of the diaphragm as it contracts

Question 135

How many vertebrae are there in the cervical, thoracic and lumbar regions of the spine? (3 marks)

Answer 135

Cervical: 7 Thoracic: 12 Lumbar: 5

Question 136

From which regions of the spine do A, B and C originate? (3 marks)

Answer 136

A) Thoracic B) Lumbar C) Cervical

Question 137

What types of joint exist between vertebrae? (2 marks)

Answer 137

Secondary cartilaginous joint (between vertebral bodies – intervertebral discs) Synovial joint (between vertebral arches – the facet/zygapophyseal joint)

Question 138

Do the vertebrae articulate with any other structures? (2 marks)

Answer 138

Yes: Ribs (costo-vertebral and costo-transverse joints; plane synovial joint) Skull/occiput (atlanto-occipital joint; condyloid synovial joint) Pelvis (sacroiliac joint; atypical synovial joint)

Question 139

Name structures 1–4 (4 marks)

Answer 139

1) Interspinous ligament 2) Ligamentum flavum 3) Supraspinous ligament 4) Posterior longitudinal ligament

Question 140

Which areas of the spinal column are most commonly fractured and why? (3 marks)

Answer 140

○ Cervical (particularly C7; C5/6 commonest level of spinal cord damage) ○ Lumbar (T12, L1/2) ○ Both are regions where areas of mobile spine (cervical and lumbar) adjoin an immobilearea (thoracic)

Question 141

What techniques could you employ to intubate a patient with an unstable cervical spine fracture? (3 marks)

Answer 141

Awake fibre-optic intubation Awake videolaryngoscopy Asleep fibre-optic intubation (+/ LMA/ILMA) Asleep laryngoscopy with cervical spine immobilisation Awake tracheostomy

Question 142

a) How can anaesthesia for carotid end arterectomy be provided?

Answer 142

Local anaesthetic infiltration Cervical epidural Cervical plexus block: Deep Deep and superficial Superficial and local anaesthetic infiltration General anaesthetic

Question 143

b) What nerve roots contribute to the cervical plexus, and where does this plexus lie?

Answer 143

Formed by branches of anterior rami of C1–4 (after they have received grey rami communicantes from the superior cervical ganglion) Lies on scalenus medius (deep to prevertebral fascia)

Question 144

c) Name the cutaneous branches of the cervical plexus (aka superficial cervical plexus) and describe their sensory distribution

Answer 144

○ Nerves emerge at the posterior border of sternocleidomastoid and pierce deep investing fascia of the neck midway between mastoid process and sternal notch( just below CN11) ○ Lesser occipital nerve (C2): Runs obliquely up along the posterior border of sternocleidomastoid Supplies scalp behind the auricle ○ Great auricular nerve (C2/3)*: Runs straight up over the belly of sternocleidomastoid Supplies skin over the cranial surface of the auricle, the external auditory meatus and lateral surface of auricle below this, also supplies angle of mandible and parotid gland/fascia ○ Transverse cervical nerve (C2/3): Travels anteriorly and divides into superior and inferior branches Supplies skin from chin/margin of mandible to sternal angle ○ Supraclavicular nerve (C3/4): Runs a short course before dividing into three main groups of branches : °Medial group: supplies skin from the midline to the anterior shoulder, as far inferiorly as the sternal angle/second rib : °Intermediate group: supplies skin over the proximal half way of deltoid muscle : ○Lateral group: supplies skin across the acromion posteriorly down to the spine of the scapula

Question 145

d) Compare and contrast general and regional techniques of anaesthesia for carotid endarterectomy

Answer 145

General: ○Advantages: : °Patient may prefer GA : °Secure airway, control ventilation : R °Reduced cerebral metabolic rate of oxygen consumption : °Removes time constraints of blocks and minimises issues with patient compliance in prolonged cases : °Noneed for intraoperative local anaesthesia supplementation Disadvantages: : °Cardiovascular instability of GA : ° Removes option of gold standard cerebral blood flow monitoring (patient interaction) : °Higher rate of shunt use : °GA may influence neurological/cognitive status/ability to assess postoperatively Regional: Advantages: : Maintains cardiovascular stability (both intra- and postoperatively) : Preservation of cerebral autoregulation : Allows continuous monitoring of cerebral blood flow/neurological function : Lower rate of shunt use : Allows earlier assessment of postoperative neurological function Disadvantages: : Conversion to GA intraoperatively may be more difficult than preoperatively : Requires patient compliance :Surgical team may not be happy with awake patient : Higher BP intraoperatively : Patient preference/claustrophobia with drapes : Patient movement : coughing, shivering if cold, restlessness/need to micturate : Potential complications from regional anaesthesia technique

Question 146

a) On the ultrasound image SOE1b, identify the muscles of the anterolateral abdominal wall (excluding rectus abdominis) and describe the orientation of their fibres

Answer 146

External oblique muscle (EO; fibres pass downwards and forwards, ‘hands in pockets’ orientation) ○ Internal oblique muscle (IO; fibres pass upwards and forwards, perpendicular to EO) ○ Transversus abdominis muscle (TA; fibres pass transversely forwards to meet in the midline)

Question 147

b) Describe their origin and insertion of abdominal muscle s

Answer 147

External oblique: ○ Origin: lower eight ribs Insertion: linea alba (via rectus sheath), pubic tubercle and anterior half of iliac crest (lower margin of EO aponeurosis between pubic tubercle and ASIS forms the inguinal ligament) ○ Internal oblique: °Origin: thoracolumbar fascia (TFL), anterior two-thirds of iliac crest and lateral two-thirds of inguinal ligament ° Insertion: costal margin, linea alba (via rectus sheath), pubic crest (pectineal line via the conjoint tendon) ○ Transversus abdominis (TA): °Origin: costal margin, TFL, anterior two-thirds of iliac crest and lateral one-third of inguinal ligament Insertion:lineaalba(viarectussheath),pubic crest (pectineal line via the conjoint tendon)

Question 148

c) In which plane does the main neurovascular bundle lie? What nerves are found here? TAP

Answer 148

Plane: deep to IO and superficial to TA (i.e. between the middle and inner layers of the anterolateral abdominal wall) Nerves: Thoracoabdominal nerves: T7–11 Subcostal nerve: T12 Iliohypogastric nerve and its collateral branch (ilioinguinal nerve): L1

Question 149

d) For which types of surgery may a transversus abdominis plane (TAP) block be beneficial?

Answer 149

○ Lower abdominal surgery (around umbilicus (T9/10) and below; open inguinal/ umbilical hernia repair, open appendicectomy, lower midline laparotomy) ○ Gynaecological/obstetric surgery (abdominal hysterectomy, caesarian section) ○ Urology (e.g. prostatectomy, nephrectomy, renal transplant)

Question 150

a) On the right-hand image of SOE1c, label the dermatomes of the upper limb

Answer 150

(C4– acromioclavicular joint/shoulder tip) C5– lateral arm C6– lateral forearm, thumb and index finger C7– middle finger C8– ring/little finger and medial forearm T1– medial arm (T2– axilla)

Question 151

b) What peripheral nerves supply the shoulder joint and skin of the shoulder region? Describe the region they supply

Answer 151

○ (Lateral) supraclavicular nerve (C3/4): skin over shoulder as far as clavicle (anteriorly), acromion (laterally) and spine of scapula (posteriorly) ○ Suprascapular nerve (C5/6): acromioclavicular joint/capsule and shoulder joint ○ Axillary nerve (C5/6): shoulder joint and ‘regimental badge’ area ○ Musculocutaneous nerve (C5/6/7): shoulder joint (and lateral forearm) ○ Lateral pectoral nerve (C5/6/7): variable innervation around anterior shoulder joint soft tissue

Question 152

c) What regional anaesthesia technique may be performed to block these nerves (roots), and which areas of the upper limb may not be blocked with this technique?

Answer 152

○ Interscalene brachial plexus block* is the most common technique (blocks proximal nerve roots of brachial plexus and distal cervical plexus– supraclavicular nerves) •Areas missed: ° Posterior shoulder (supraclavicular nerve: this area often must be augmented by local anaesthetic infiltration at the posterior port site for awake arthroscopic shoulder surgery) ° Ring/little finger, medial forearm/arm and axilla (C8–T2: inferior roots of brachial plexus are not as well visualised in the interscalene grove and therefore may be missed, often blockade here is not required) *A shoulder block has also been described: Separate axillary and suprascapular nerve blocks Avoids phrenic nerve block and therefore may be useful in patient with significant respiratory limitation

Question 153

d) Name structures A–F on the ultrasound image in SOE1c of the interscalene groove

Answer 153

A) Nerve roots (C5–7) B) Scalenus anterior muscle C) Vertebral artery D) Sternocleidomastoid muscle E) Scalenus medius muscle F) Phrenic nerve

Question 154

e) List the possible neurological complications of an interscalene block

Answer 154

○ Cervical cord injury (by needle trauma/injection) ○ Epidural/subarachnoid injection of local anaesthesia ○ Phrenic nerve blockade (approaching 100% in high-volume block, symptomatic in around 30%) ○ Cervical sympathetic chain block (Horner’s syndrome) ○ Vagal nerve block/injury or recurrent laryngeal nerve block/injury Injury to nerve roots of brachial plexus ○ There is some concern that, using an in-plane technique, the dorsal scapular nerve and long thoracic nerves can be damaged by direct needle trauma as they lie on scalenus medius ○ Vascular trauma (vertebral artery): bleeding and intravascular injection/toxicity/seizure

Question 155

a) Describe the blood supply to the spinal cord

Answer 155

Single anterior spinal artery: ○Formed from the union of a branch of each vertebral artery at the foramen magnum ○Descends whole length of spinal cord in anterior median fissure ○ Gives series of circumferential and central branches ○Supplies anterior two-thirds of spinal cord: all of cord anterior to posterior grey columns Two posterior spinal arteries: ○From posterior inferior cerebellar artery (75%) or vertebral artery (25%) at foramen magnum ○Usually double on each side; trunks run through and behind posterior nerve rootlets for whole length of the cord Radicular arteries: ○ Important contribution as the longitudinal arteries (above) are variable in size ○ Anastomosing with and reinforce anterior and posterior spinal arteries ○ Arise from vertebral, posterior intercostal, lumbar and lateral sacral arteries ○ Enter through intervertebral foramina as spinal arteries ○ Penetrate meninges and run along nerve roots ○ Variable in number; not present at all levels ○ Largest: arteria radicularis magna (artery of Adamkiewicz), usually from lower intercostal or upper lumbar artery (T8–L3), on the left in 80% (in 15% arises at T5) Spinal veins: ○ One anterior spinal vein, one posterior spinal vein (on posterior median sulcus) and two posterolateral spinal veins (lateral to posterior spinal arteries) ○ Drain via internal vertebral venous plexus to external vertebral venous plexus, and then to vertebral, azygos, lumbar and lateral sacral veins

Question 156

b) Where are the ‘watershed areas’ in relation to blood supply of the spinal cord?

Answer 156

Found at junctions of cervical, thoracic and lumbar regions of cord, where the blood supply is tenuous and the cord is vulnerable to ischaemia (particularly at T4/5)

Question 157

c) On the illustration SOE1d, label the main ascending and descending tracts in the spinalspinal cord, and describe the signals they transmit

Answer 157

Ascending: Anterior (direct) and lateral (crossed) spinothalamic tracts (pain,temperature, touch) Dorsal column-medial lemniscal: fasciculus cuneatus (C1–T6) and gracilis (T7 and below) (vibration, proprioception, touch) Anterior and posterior spinocerebellar (unconscious proprioception: muscle length/ tension) Descending: Anterior (direct) and lateral (crossed) corticospinal tracts (voluntary movement)

Question 158

d) Which surgical procedures are associated with spinal cord ischaemia?

Answer 158

○ Aortic aneurysm repair (particularly thoracoabdominal) ○ Aortic dissection ○ Scoliosis surgery ○ Laminectomy/spinal decompression ○Procedures causing periods of significant hypotension

Question 159

e) How can you prevent intraoperative spinal cord ischaemia?

Answer 159

○ Maintain adequate MAP: •Judicious monitoring (e.g. arterial line) •Appropriate use of IV fluids and vasoconstrictors/inotropes ○ CSF drain (to reduce CSF pressure and increase spinal cord perfusion) ○ Minimise duration of aortic cross-clamp ○ Consider cardiopulmonary bypass or deep hypothermic circulatory arrest ○ Monitoring of somatosensory evoked potentials ○ Intrathecal vasodilators (e.g. papaverine), systemic Ca2+ channel blockers

Question 160

a) Describe the anatomy of the trigeminal nerve (CN 5)

Answer 160

○ Single motor nucleus: ° Trigeminal motor nucleus (pons; motor to muscles of mastication and four others*) ○ Three sensory nuclei: °Trigeminal mesencephalic nucleus (midbrain; proprioception) °Trigeminal pontine (principal) nucleus (pons; touch) °Trigeminal spinal nucleus (medulla; pain/temperature) - Arises from the pons as a large sensory root and a smaller motor root ○ The majority of sensory fibres have their cell body located in the trigeminal ganglion** (aka semilunar/Gasserian ganglion), lying within an evagination of arachnoid dura (cavum trigeminale/Meckel’s cave) near the apex of the petrous temporal bone in the middle cranial fossa Three sensory branches emerge: V1 (ophthalmic): passes forwards in lateral wall of cavernous sinus, divides into lacrimal, frontal (further divides: supraorbital and supratrochlear) and nasociliary branches, which exit middle cranial fossa through superior orbital fissure V2 (maxillary): passes forwards in lateral wall of cavernous sinus, leaves middle cranial fossa through foramen rotundum ○ V3 (mandibular): passes inferiorly through foramen ovale, then joined by motor root to form a trunk that splits into two divisions (anterior is mainly motor and posterior is mainly sensory) *Muscles supplied by CN 5: Muscles of mastication: masseter, temporalis, medial pterygoid, lateral pterygoid Four others: tensor tympani, tensor palati, anterior belly of digastric, mylohyoid **Equivalent to the dorsal root ganglion of a spinal nerve

Question 161

b) Draw a diagram to describe the sensory supply of CN 5

Answer 161

○ Sensation to face and scalp, from chin to vertex and ear to ear (but not angle of jaw) ○ Anterior meninges (dura and arachnoid) Eye, nasal and oral cavities (including inside of cheek, mandible, teeth and gums) ○ General sensation to anterior two-thirds of tongue (but not taste***) ***Supplied by chorda tympani of CN 7

Question 162

c) What is trigeminal neuralgia (TN)?

Answer 162

○ Episodic, severe, lancinating pain in CN 5 territory (V1/V2 more common, V3 rare) ○ Always unilateral, typically abrupt onset/offset ○ May develop allodynia or hyperalgesia (but no other neurological deficit) ○ Usually asymptomatic between paroxysms ○ May be no clear cause, but have various triggers (e.g. touch, shaving) ○ International Headache Society diagnostic criteria (ICHS Classification ICHD-3): • Recurrent paroxysms of unilateral facial pain in the distribution of one or more division of CN 5, with no radiation beyond, and fulfilling the following criteria: A: lasting up to two minutes + severe + electric shock-like/stabbing/sharp (duration can change over time) : B: triggered by innocuous stimuli within the CN 5 distribution (attacks can be may appear to be spontaneous, but must be a history of pain provoked by stimuli) : C: not better accounted for by another ICHD-3 diagnosis

Question 163

d) What are the risk factors for trigeminal neuralgia and how is the diagnosis made?

Answer 163

Risk factors: Female (F:M 2:1) Age (rare before 50 years, peak onset 60–70 years) Occurs in 3–4% of patients with multiple sclerosis (MS) (often in younger patients) There is an association with hypertension Possibly a familial link (suggested to be a result of inherited blood vessel malformation) Diagnosis: Clinical, from the history MRI can help exclude brainstem lesion and vascular malformation

Question 164

e) What causes TN?

Answer 164

Unclear ○ Primary/secondary demyelination of CN 5 leads to uncontrolled firing of small fibres (e.g. secondary demyelination due to compression by one of the cerebellar arteries) ○ Occurs partly because of lack of inhibitory input from large myelinated fibres (e.g. in MS, due to blood vessel compressing nerve) ○Central mechanism also suggested

Question 165

f ) Describe the management of TN

Answer 165

○ Conservative Psychological support may be important for resistance/poorly responsive cases ○ Medical Cabamazepine (effective in >90%, if no response reconsider diagnosis) ○ Phenytoin second line ○ Other agents: gabapentin, amitriptyline, baclofen, clonazepam, lamotrigine ○ Surgical/interventional ° Alcohol injection at various points along the nerve (now rarely performed) ° Glycerol injection of the trigeminal ganglion (both aim to selectively destroy pain fibres, glycerol technique has higher success rate) ° Balloon decompression (destroying sensory fibres) ° Gammaknife techniques (stereotactic-guided radio-ablation: needle passed through foramen ovale into trigeminal ganglion, benefit may take months to develop) ° Open microvascular decompression of CN 5 (effective in >80%, previously only done if imaging demonstrated a vessel compressing the nerve, but may be effective even if preoperative imaging does not show this)

Question 166

a) What are the pleural membranes and where are they found?

Answer 166

○ Pair of serous membranes (thin membrane of fibrous tissue with single layer of squamous cells; mesothelium) ○ Parietal pleura: Lines inner surface of the thorax, mediastinum and upper surface of the diaphragm Bound to inner surface of thoracic cage by endothoracic fascia Bound superiorly at thoracic inlet to suprapleural membrane (Sibson’s fascia) ○ Visceral pleura covers the surface of each lung (including fissures) Parietal and visceral pleura are in contact and lubricated by a thin film of tissue fluid

Question 167

b) Describe the surface markings of the pleura with reference to the photograph of the thoracic skeleton

Answer 167

○ 2.5 cm above the junction of the middle and medial thirds of the clavicle (but not above the neck of the first rib) ○ In the midline at the 2nd rib (sternal angle) ○ At 4th costal cartilage: • Right side continues vertically down • Left side sweeps out and descends behind the costal cartilages Both pleura pass behind the 6th costal cartilage ○ Midclavicular line: 8th costal cartilage ○ Midaxillary line: 10th rib ○ Midscapular line (lateral border of erector spinae): 12th rib Passes horizontally to the lower border of T12 (Note that a triangle of pleura lies below the medial part of the 12th rib) *Easy: 2–4-6–8-10–12! (See bold numbers in text)

Question 168

c) What are the costodiaphragmatic and costomediastinal recesses and where are they found?

Answer 168

○ The lungs only occupy the full space indicated by the surface markings of the pleura at the peak of inspiration ○ At other times, below the inferior border of the lung the costal and diaphragmatic parietal pleura are in contact (separated by a thin layer of tissue fluid) ○ The potential space found here is the costodiaphragmatic recess ○ The same is true of the potential space between the costal and mediastinal parietal pleura anteriorly **The lungs don’t always occupy the whole pleural space, creating recesses: The anterior borders of the lungs are similar (apart from a slightly larger ‘cardiac notch’ for the left lung) 6th costal cartilage in midclavicular line 8th rib in midaxillary line 10th rib in midscapular line Pass medially to T10

Question 169

c) What are the costodiaphragmatic and costomediastinal recesses and where are they found?

Answer 169

> The lungs only occupy the full space indicated by the surface markings of the pleura at the peak of inspiration > At other times, below the inferior border of the lung the costal and diaphragmatic parietal pleura are in contact (separated by a thin layer of tissue fluid) > The potential space found here is the costodiaphragmatic recess > The same is true of the potential space between the costal and mediastinal parietal pleura anteriorly **The lungs don’t always occupy the whole pleural space, creating recesses: > The anterior borders of the lungs are similar (apart from a slightly larger ‘cardiac notch’ for the left lung) 6th costal cartilage in midclavicular line 8th rib in midaxillary line 10th rib in midscapular line Pass medially to T10

Question 170

d) Describe the innervation of the pleura

Answer 170

Parietal: ° Intercostal nerves supply the costal and peripheral diaphragmatic parts ° Phrenic nerve supplies mediastinal parts and central portion of the diaphragmatic parts Visceral: Sympathetic nociception and vasomotor

Question 171

e) What are the indications for an interpleural block?

Answer 171

Surgery (thoracotomy, chest wall surgery, upper abdominal laparotomy) Trauma (analgesia for rib fractures, chest drain insertion) Chronic pain (post herpetic neuralgia, cancer pain, pancreatitis)

Question 172

f ) Outline how to perform an interpleural block

Answer 172

• Consent • Stop before you block: confirm side and site SLIMRAG: ° Sterile procedure (wash hands, sterile gloves, sterile dressing pack) ° Light source/ultrasound IV access ° Monitoring (AAGBI minimum standard) ° Resuscitation drugs/equipment available ° Assistant (who is happy to assist with regional or general anaesthetic) ° General anaesthetic (ensure equipment/drugs available to convert if required) ° Equipment: 16 G Tuohy needle connected to a three-way tap and a bag of normal saline ° Position the patient (supine or lateral, flat or semirecumbent) ° Clean skin with 0.5% chlorhexidine (allow to dry) ° Local anaesthetic to skin ° Needle insertion point (various described): Anterior/mid/posterior axillary line or 10 cm from dorsal midline, in the 4th to 8th intercostal space ° Midclavicular line, 2nd intercostal space ° Avoid the neurovascular bundle below the rib (N.B. there is also a lesser neurovascular bundle above each rib) ° Insert Tuohy needle through skin and connective tissue until contact is made with the rib ° Open three-way tap to bag of fluid ° Advance the needle during expiration (spontaneously breathing patient) or at the end of expiration with the ventilator disconnected (mechanically ventilated patient) ° Walk the needle off the superior border of the rib ° Advance the needle until fluid runs freely from the bag of saline (thus identifying the negative pressure of the interpleural space) ° Open three-way tap to inject local anaesthetic (e.g. 30 ml 0.25% L-bupivacaine) into the interpleural space (Insert catheter if required) ° Withdraw the needle

Question 173

SOE 2c a) Describe the boundaries of the cubital fossa with reference to the cadaveric image SOE2c

Answer 173

○ Proximal: line joining the medial and lateral epicondyles of the humerus ○ Inferolateral: medial border of brachioradialis ○ Inferomedial: lateral border of pronator teres ○ Roof: deep fascia of forearm (reinforced by the bicipital aponeurosis) ○ Floor: brachialis, capsule of elbow joint, supinator muscle

Question 174

b) What are the contents of the cubital fossa?

Answer 174

Biceps tendon Brachial artery (dividing into radial and ulnar arteries) Median nerve

Question 175

c) Name the superficial veins associated with the cubital fossa, the areas they drain and where they drain to.

Answer 175

○ Cephalic (drains lateral side of forearm, runs ○ Basilic (drains medial side of forearm, runs up medial side of arm and pierces deep fascia half way up the arm, to join the venae commitantes of the brachial artery and form the axillary vein at the inferior border of teres major) ○ Median cubital (connects cephalic and basilic veins, lies over the bicipital aponeurosis) ○ Variations in the pattern of these veins are common *TAN: Tendon Artery Nerve The radial nerve is included in some descriptions, lying between brachioradialis and brachialis up lateral edge of biceps to deltopectoral groove and pierces clavipectoral fascia to drain into the axillary vein)

Question 176

d) What are the features of inadvertent intra-arterial injection here? Cubical fossa

Answer 176

• May be asymptomatic • The drug may fail to elicit the expected effect • Pain and paraesthesia (if patient awake) in the hand • Ischaemic changes (vasospasm): cool, pale, mottled, cyanosed • May be unable to feel distal pulses (may ultimately develop oedema and tissue necrosis)

Question 177

a) A six-month-old, otherwise well, boy is to undergo general anaesthesia for an inguinal hernia repair. What analgesic options would you consider?

Answer 177

Paracetamol NSAID Opiate (fentanyl under anaesthesia) Local anaesthetic in wound TAP/ilioinguinal nerve block Caudal block

Question 178

b) For what type of surgery may a caudal block provide adequate analgesia?

Answer 178

> Most types of surgery of the abdomen/pelvis/genitalia/perineum below the umbilicus > General surgery: inguinal hernia repair, distal gastrointestinal tract (e.g. rectum/anus > Urology: orchidopexy/orchidectomy, hypospadias repair, circumcision (Sometimes lower limb plastic/orthopaedic surgery)

Question 179

c) Describe the anatomy of the sacrum

Answer 179

○ Triangular bone at the bottom of the spine, formed by five fused sacral vertebrae ○ Wedged between hip bones, only the superior part is weight bearing (transmits weight of body to pelvic girdle) ○ Concave (more in males) ○ Base (uppermost, tilted anteriorly), apex and four surfaces (anterior, posterior and two lateral surfaces) ○ Central mass: formed by the fusion of five vertebral bodies ○Laterally: two lateral masses (alae, wings), articulate with ilium at auricular surfaces (synovial joint) ○ Anterior surface: Sacral promontory ○ Four transverse lines (represent fusion of vertebral bodies; complete after 20th year) ○ Anterior sacral foramina ○ Dorsal surface: Median crest (fused spinous processes), medial/intermediate crest (fused articular processes) and lateral crest (fused transverse processes) ☆ Dorsal sacral foramina ☆°Sacral hiatus (absence of spine and failure of fusion of laminae of S5 +/S4) ☆ Sacral cornua (articular processes of 5th sacral vertebra) ☆ Sacral hiatus closed by superficial sacrococcygeal ligament (sacrococcygeal membrane) ☆ Sacral canal: Triangular, continuous with vertebral canal above, contains nerve roots of caudal equina ☆ Contains: termination of dural sac (sacral nerves and filum terminale), areolar connective tissue, venous plexus, lymphatics Filum terminale internum: dural sac attaches to back of S2 vertebra Filum terminale externum: continuation of pia attached to back of coccyx

Question 180

d) What are the anatomical considerations with regard to paediatric neuroaxial blockade?

Answer 180

Spinal cord ends at L1/2 in adults, L3 in children Dura ends at S2 in adults, S4 in children (adult level by age of 2 years)

Question 181

e) How can you identify the sacral hiatus?

Answer 181

Apex of equilateral triangle completed by PSIS on each side With hips flexed at 90°, longitudinal axis of femur points to sacral hiatus Palpate the median (midline) sacral crest inferior until the cornua are identified

Question 182

f ) What dose of 0.25% levo-bupivacaine would you use for this surgery?

Answer 182

> Armitage formula (1979) for 0.25% levo-bupivacaine: - Sacral block: 0.5 ml/kg (circumcision, hypospadias, anal procedures) - Low thoracic block: 1 ml/kg (hernia repair) - Midthoracic (T8): 1.25 ml/kg (e.g. orchidopexy)

Question 183

What are the contraindications and complications of a caudal block?

Answer 183

Contraindications: ○ Lack of parental consent ○ Lack of patient assent (older children) ○ Local/systemic infection ○ Coagulopathy ○ Local anaesthetic allergy (or toxicity) ○ Raised ICP ○ CV instability (in children >6 years) Complications: ○ Failure ○ Incorrect injection site: IV, IO, subdural/intrathecal, subcutaneous ○ Drug reaction: local anaesthetic systemic toxicity, allergy to injected drugs ○ Effects of local anaesthetic: motor block, urinary retention ○ Epidural haematoma ○ Bowel perforation ○ Infection

Question 184

On the image SOE3a, name the (seven pairs of ) nerves targeted in a scalp block. Describe the region they supply

Answer 184

Supraorbital nerve: ° The larger branch of the frontal nerve (CN 5.1) ° Through supraorbital notch to supply forehead, upper eyelid and anterior scalp (to vertex) Supratrochlear nerve: ° The smaller branch of the frontal nerve (CN 5.1) ° Innervates medial forehead, bridge of nose and medial portion of upper eyelid Zygomaticotemporal nerve: ° Branch of the zygomatic nerve (CN 5.2) ° Passes through the zygomaticotemporal foramen of the zygoma, and then through temporalis muscle, to pierce the temporalis fascia ° Sensory innervation of lateral forehead and anterior temporal region (‘hairless’ part of temple) Auriculotemporal nerve: ° Branch of CN 5.3 ° Crosses zygomatic process of the temporal bone with the superficial temporal artery ° Innervates lateral surface of auricle, external auditory meatus, outer tympanic membrane and posterior temporal region (‘hairy’ part of temple) Lesser occipital nerve: ° From anterior ramus of C2 ° Ascends obliquely along the posterior border of sternocleidomastoid Provides sensory innervation to the scalp behind the auricle Greater occipital nerve: ° Medial branch of the posterior ramus of C2 Sensory innervation to the skin over the occiput and posterior scalp (up to the vertex), and posterior neck Great auricular nerve (remember– no greater auricular nerve!) ° A branch of the (superficial/sensory) cervical plexus, with root values C2–3 ° Emerges from behind the posterior border of sternocleidomastoid and travels directly up to supply the lateral surface of the auricle (below EAM) and all of its cranial surface, as well as skin over the parotid and angle of jaw

Question 185

Which of these nerves are derived from cranial nerves (and from which one)? Scalp block

Answer 185

Sensory innervation of lateral forehead and anterior temporal region (‘hairless’ part of temple) ○ Auriculotemporal nerve: °Branch of CN 5.3 °Crosses zygomatic process of the temporal bone with the superficial temporal artery °Innervates lateral surface of auricle, external auditory meatus, outer tympanic membrane and posterior temporal region (‘hairy’ part of temple) ○ Lesser occipital nerve: From anterior ramus of C2. •Ascends obliquely along the posterior border of sternocleidomastoid •Provides sensory innervation to the scalp behind the auricle ○ Greater occipital nerve: Medial branch of the posterior ramus of C2 Sensory innervation to the skin over the occiput and posterior scalp (up to the vertex), and posterior neck ○ Great auricular nerve (remember– no greater auricular nerve!) °A branch of the (superficial/sensory) cervical plexus, with root values C2–3 °Emerges from behind the posterior border of sternocleidomastoid and travels directly up to supply the lateral surface of the auricle (below EAM) and all of its cranial surface, as well as skin over the parotid and angle of jaw

Question 186

c) What are the indications for a scalp block?

Answer 186

Awake craniotomy Postcraniotomy analgesia Analgesia for scalp wound/suturing

Question 187

d) What landmarks are used to block each of these nerves as part of a scalp block?

Answer 187

1. Supraorbital: supraorbital notch, inject immediately above periosteum 2. Supratrochlear: medial to supraorbital notch, inject immediately above periosteum (single midbrow skin insertion point can be used for bilateral blocks) 3. Zygomaticotemporal: from lateral edge of orbital margin along length of zygomatic arch, inject deep and superficial to temporalis muscle 4. Auriculotemporal: 1 cm anterior to the auricle (palpate superficial temporal artery to avoid accidental intra-arterial injection; nerve and artery lie together) 5. Lesser occipital: infiltrate at a point two-thirds of the way along a line from the external occipital protuberance to the mastoid process 6. Greater occipital: infiltrate at a point one-third of the way along a line from the external occipital protuberance to the mastoid process (greater occipital nerve runs with the occipital artery) 7. Great auricular: infiltrate 2 cm posterior to auricle, over the mastoid process, level with tragus

Question 188

Use the diagram SOE3b to describe the fetal circulation, starting at the umbilical vein

Answer 188

Oxygenated blood returns from the placenta via the (left) umbilical vein (The right umbilical vein obliterates during fetal development) This joins the left branch of the portal vein in the porta hepatis Most (>60%) travels to the IVC via the ductus venosus, bypassing the hepatic circulation On returning to the right atrium, oxygenated blood from the IVC travels across the foramen ovale to the left atrium From the left atrium blood passes to the left ventricle and out into the ascending aorta, perfusing the carotid arteries Deoxygenated blood returning from the head and neck via the SVC passes through the right atrium (mixing very little with oxygenated blood from the IVC) to the right ventricle, and out into the pulmonary trunk 90% of this blood bypasses the lungs via the ductus arteriosus, which opens into the aorta distal to the three branches of the arch of the aorta (preventing venous blood from perfusing the head and neck) This deoxygenated blood then travels in the descending aorta and through the common iliac arteries, then (anterior division of the) internal iliac arteries, and finally the umbilical artery to the placenta

Question 189

Label the diagram with approximate oxygen saturation of blood at the following points: • Umbilical vein • IVC • Ascending aorta • Ductus arteriosus • Descending aorta

Answer 189

○ Umbilical vein– 80% ○ IVC– 67% ○ Ascending aorta– 62% ○ Ductus arteriosus– 50% ○ Descending aorta– 58%

Question 190

What are the physiological changes that occur at birth?

Answer 190

When the neonate inspires, the expanding and newly oxygenated lung tissue causes a dramatic reduction in pulmonary vascular resistance ○ As pulmonary blood flow increases, so does pulmonary venous return ○ Clamping of the umbilical cord raises systemic vascular resistance and aortic pressure ○°This raises left atrial pressure, causing closure of the foramen ovale ○ As the pressure gradient across the left and right side of the circulation reverses, this reduces (or even reverses) blood flow across the ductus arteriosus ○ The ductus arteriosus closes via contraction of its muscular wall due to higher partial pressures of oxygen and chemical mediators (e.g. decreasing prostaglandins) ○ Obliteration of the ductus arteriosus can take from two weeks to two months

Question 191

Describe the development and structure of the foramen ovale

Answer 191

At early stages of embryonic development, a single atrium is present ○ An initial partition grows down from the posterosuperior wall (septum primum) to meet the endocardial cushions, which divide the embryonic atria from ventricles ○ Before the two atria are completely divided, a perforation develops in the septum primum, the foramen secundum (the foramen primum being the initial communication between the two sides of the atrium) ○ A second partition then develops on the right of the septum primum (the septum secundum)The septum secundum has a free lower border, but is large enough to overlap the foramen secundum ○ This creates a flap-valve effect: @° When the right atrium is at higher pressure, the septum primum deviates to the left, allowing blood to pass through the space between the foramen secundum and septum secundum (from right to left) ° However, when the left atrium is at higher pressure, the septum primum is compressed against the septum secundum, closing the channel *This version is derived from a particularly excellent description in Ellis and Mahedevan’s ‘Clinical Anatomy: Applied Anatomy for Students and Junior Doctors’ (12th Edition, 2010; pp. 40–4)– the authors encourage readers to review this account

Question 192

What is meant by a paradoxical embolus?

Answer 192

○ This refers to an embolus that is carried from the venous side of the adult circulation to the arterial side (or vice versa) ○ It can cross via a defect in the heart, such as a patent foramen ovale (or ASD/VSD), or via AV shunts in the lungs ○ They represent around 2% of emboli

Question 193

Describe the arterial supply of the lower limb

Answer 193

○ The arterial supply is from the femoral artery, a continuation of the external iliac artery, entering the thigh under the inguinal ligament at the midinguinal point* ○ It initially lies in the lateral compartment of the femoral sheath, medial to the femoral nerve and lateral to the femoral vein ○ Gives four small branches in the groin and courses distally in the femoral triangle, then in the adductor canal (under sartorius), lying on the anterior surface of muscles in the medial (adductor) compartment of the thigh ○ In this course it gives off the profunda femoris (which passes posteriorly to supply the hip joint via circumflex branches and the posterior compartment of the thigh by perforating branches) ○ It leaves the adductor canal by passing round the medial border of the femur (through the ‘adductor hiatus’–defect in attachment of adductor magnus to the femur) and enters the popliteal fossa as the popliteal artery (where it gives branches to the knee joint) ○ Divides at the lower border of popliteus into the posterior and anterior tibial arteries** ○ The posterior tibial artery travels distally in the posterior compartment of the leg (calf ); its most important branch is the peroneal artery (which supplies, but does not lie in, the lateral compartment of the leg) ○ The posterior tibial artery passes behind the medial malleolus (where it is anterior to the tibial nerve), to enter the foot and divide into medial and lateral plantar arteries ○ The anterior tibial artery travels in the anterior compartment of the leg and crosses the line of the ankle joint to become the dorsalis pedis artery *Don’t confuse these two locations: Midinguinal point: halfway between the ASIS and midline/pubic symphysis (where the femoral artery is found) Midpoint of the inguinal ligament: halfway between ASIS and the pubic tubercle (where the femoral nerve is found) **Vascular surgeons/radiologists use slightly different terminology to anatomists and may refer to the above structures in these terms: Common femoral artery (CFA; from inguinal ligament to origin of profunda femoris) Deep artery of the thigh (profunda femoris) Superficial femoral artery (SFA; femoral artery from origin of profunda femoris to adductor hiatus) Tibioperoneal trunk (TPT; the short segment of the posterior tibial artery, before the peroneal artery arises)

Question 194

Describe the course of the great/long saphenous vein

Answer 194

Begins as a continuation of the dorsal venous arch, on the medial side of the dorsum of the foot Lies in front of the medial malleolus and courses proximally, following an oblique course across the superficial surface of the distal tibia (from anterior to posterior) Passes a hand’s breadth behind the medial border of the patella, then courses up the anteromedial thigh to enter the femoral vein at the saphenous opening

Question 195

Name the principal superficial vein on the posterior surface of the leg

Answer 195

Small/short saphenous vein

Question 196

With which nerves do these two supeficial veins run in the leg?

Answer 196

Great/long saphenous vein: saphenous nerve (from the femoral nerve) Small/short saphenous vein: sural nerve (from the tibial and common peroneal nerves)

Question 197

Name two sites for intraosseous vascular access in the lower limb

Answer 197

Proximal tibia (2 cm medial and 2 cm below the tibial tuberosity, on the medial/ subcutaneous surface) Distal tibia (around 3 cm proximal to the medial malleolus, on the medial/ subcutaneous surface) Distal femur (around 3 cm above and 2 cm medial to the lateral epicondyle)

Question 198

Name the indications and contraindications to intraosseous access

Answer 198

○ Any clinical situation requiring blood sampling or vascular access (but this is not immediately possible) ○ Inability to gain vascular access in emergency management where intravascular access/drugs/fluids are required (e.g. trauma, shock) ○ During CPR (particularly in children) Contraindications: ○ Site of bone fracture Ipsilateral fracture of the extremity (particularly in the same bone) ○ Difficulty identifying anatomy ○ Infection (or burn) at site of entry ○ Site of previous attempt/access within 48 hours (or different sites on same bone) ○ Compartment syndrome in same limb ○ Site of prosthesis

Question 199

Describe the bony structure of the orbit

Answer 199

○ Four-sided pyramid, lying on its side ○ The base lies anteriorly and apex posteriorly (on the optic canal/medial end of the superior orbital fissure) ○ Medial walls lie in parallel and lateral walls diverge at 90° (continuing these lines posteriorly, they would meet at the pituitary fossa)* ○ Roof: Orbital plate of frontal bone Lesser wing of sphenoid ○ Floor: Orbital surface of maxilla Partly by zygomatic and palatine bones ○ Medial wall: Orbit plate of ethmoid bone (lamina papyracea) Contributions from the maxilla, lacrimal and sphenoid • Lateral wall (longest, thickest and strongest part of the orbit): Zygomatic bone Greater wing of sphenoid *Note that the axes of the orbit and globe are different: The axis of the orbit bisects the medial and lateral walls, i.e. lies along a plane that runs from posteromedial to anterolateral The axis of the globe lies on a direct anteroposterior plane

Question 200

On this image of the orbit, identify features A–E

Answer 200

A) Optic canal B) Superior orbital fissure C) Inferior orbital fissure D) Supraorbital foramen (more commonly the foramen is not complete, when it is termed the supraorbital notch) E) Infraorbital groove, canal and foramen

Question 201

Which areas do A and B run between, and what structures do they transmit?

Answer 201

A) Optic canal: ○ Canal through the lesser wing of the sphenoid bone ○ Connects orbit to middle cranial fossa ○ Transmits CN 2 and the ophthalmic artery B) Superior orbital fissure: ○ Cleft between greater and lesser wings of sphenoid ○ Connects orbit and middle cranial fossa ○ Divided into three compartments by the common tendinous origin/ring (annulus of Zinn), which gives rise to rectus muscles in the orbit • Lateral compartment: lacrimal (CN 5.1), frontal (CN 5.1) and trochlear (CN 4) nerves, superior ophthalmic vein • Intermediate compartment (within the tendinous ring): oculomotor (CN 3; superior and inferior divisions), abducens (CN 6) and nasociliary (CN 5.1) nerves • Medial compartment: inferior ophthalmic vein

Question 202

Which areas do A and B run between, and what structures do they transmit?

Answer 202

A) Optic canal: ○ Canal through the lesser wing of the sphenoid bone ○ Connects orbit to middle cranial fossa ○Transmits CN 2 and the ophthalmic artery B) Superior orbital fissure: ○ Cleft between greater and lesser wings of sphenoid ○ Connects orbit and middle cranial fossa ○ Divided into three compartments by the common tendinous origin/ring (annulus of Zinn), which gives rise to rectus muscles in the orbit °Lateral compartment: lacrimal (CN 5.1), frontal (CN 5.1) and trochlear (CN 4) nerves, superior ophthalmic vein °Intermediate compartment (within the tendinous ring): oculomotor (CN 3; superior and inferior divisions), abducens (CN 6) and nasociliary (CN 5.1) nerves °Medial compartment: inferior ophthalmic vein

Question 203

What is the nerve supply to the eye?

Answer 203

Sensory: ○ CN 2 (vision) ○ CN 5.1 (general sensation, via long and short ciliary nerves, which come from nasociliary nerves) Sympathetic: ○ T1 fibres that synapse in the superior cervical ganglion ° Travel superiorly in the neck in the carotid plexus ° Join CN 5.1 in the cavernous sinus ° Pass forwards through the superior orbital fissure on the nasociliary nerve, then the long ciliary nerves ° Stimulation leads to contraction of the radial muscles of the iris (dilator pupillae) causing pupil dilation Parasympathetic: ○ From the Edinger Westphal nucleus accompanying CN 3 (inferior division) ° Synapse in the ciliary ganglion, then run in the short ciliary nerves ° Stimulation leads to contraction of the ciliary muscle (lens accommodation) and the sphincter pupillae muscle (pupil constriction)

Question 204

What blocks are used to provide anaesthesia in surgery on the eye?

Answer 204

> Topical administration of local anaesthesia > Peribulbar block (outwith cone of muscles that surround the globe: the muscles have a thin fibrous layer running between them, so larger volumes (5–15 ml) of local anaesthetic are administered, which diffuses into the cone to contact the nerves) > Retrobulbar block(outwith > Tenon’s capsule of the globe but within the surrounding cone of muscles/fascia, therefore smaller volumes (3–5 ml) of local anaesthetic needed) > Sub-Tenon’s block (injection of local anaesthetic under the capsule of the eye, which is continuous with the cuff of dura around the optic nerve)