Flashcards in Peripheral nerve Deck (159):
What muscles cause shoulder adduction?
How do you test for serratus anterior?
Anterior flexion of the arm and feel the medial scapula
How do you test the rhomboid muscles (C5)?
Pull shoulder blades together
How do you test the teres minor (C5/6)?
Shoulder external rotation (nerve supply is Axillary nerve)
What is the nerve supply to brachioradialis?
C5/6 Radial nerve
What is the nerve supply to triceps?
Radial nerve C6/7/8 above the spiral groove
What muscles cause wrist extensors?
Ext carpi radialis longus and brevis and Ext carpi ulnaris
Which muscles flex the wrist?
Flex carpi radialis (median), Flex carpi ulnaris and palmaris longus
What muscles are supplied by the median nerve in the hand?
What muscles in the hand are supplied by the ulnar nerve?
Interossei, adductor pollicis (Froments sign), hypothenar eminance and ulnar lumbricals
For peripheral nerve history what should you ask about?
Motor, sensory and pain followed by EMG/NCS and imaging
How do you test gluteus maximus?
Abduction of the hip
How do you differentiate common peroneal nerve vs L5 root compression?
History - pain starts in the back vs knee
Examination - Tibialis anterior (deep peroneal) - causes ankle dorsiflexion; Posterior tibitalis (L5 tibial nerve) - causes plantar flexion and inversion;
Superficial peroneal nerve - causes eversion of the ankle;
Gluteus medius (L5 root to superior gluteal nerve) causes hip abduction
What are the causes of peripheral nerve disease?
What are the options to repair a nerve?
When should a peripheral nerve repair be undertaken?
Sharp injury (cut nerve) 1 year (tendon transfer etc)
At what rate do peripheral nerves regrow?
1 inch a month
Why would a posterior cord of the brachial plexus injury cause a wrist drop?
Radial nerve involvement
What should you consider in a patient with a posterior cord injury?
Brachial plexus injury
How can you test if a nerve is in continuity following an injury?
USS or MRI and NCS (looking for action potentials)
Note the action potentials across the injury segment if in continuity allows you to wait. If no action potentials then needs repair.
EMG will not help as the nerve will not have grown back to the muscle by then (1mm per day)
What roots supply the upper trunk of the brachial plexus?
What injury occurs with an upper trunk brachial plexus injury?
C5 and C5 so loss of shoulder abduction and elbow flexion
What would you do if there is no AP across a neuroma?
Which nerve is injured following a LN biopsy in the posterior triangle?
Spinal accessory - unable to shrug shoulder / abduct as the trapezius stabilises the scapula
Which 3 nerve injuries cause winging of the scapula?
Long thoracic nerve (to serratus anterior)
Spinal accessory (to trapezius)
Dorsal scapula nerve (to rhomboid)
Does an injury to the thoracodorsal nerve cause winging of the scapula?
No! it supplies latissimus dorsi
What nerves can be used for nerve graft repairs?
Sural nerve most commonly used
When is a graft nerve repair undertaken?
When there is a gap between the two ends of the nerve
What is Erbs palsy?
Waiters tip position due to upper trunk injury causing C5/6 injury
How would you manage Erbs palsy in a child?
Wait 3 months
If no repair then surgery with action potentials and repair if neuroma is non-conducting
What is a stinger/burner?
This is acute nerve pain secondary to a peripheral nerve injury which is transient (few seconds)
What is the most common pattern of a stinger?
What is a neurotization?
When is a nerve transfer performed?
Preganglionic nerve injury (root avulsion) +/- postganglionic injury
How can you perform a nerve transfer for a patient with a C5/6 avulsion?
Fascicular transfer using fascicles of the intact ulnar nerve and transfer it to the biceps motor nerve (Muscluocutaneous nerve) to give elbow flexion and transfer a fascicle of the radial nerve to trapezius.
What is Erbs point?
The site where the C5/6 roots join to form the upper trunk
How would you manage a patient with a complete brachial plexus injury?
Wait 3 months - if no recover then:
Preop CT myleogram
Intraoperative monitoring (nerve APs)
Target shoudler and elbow flexion
Nerve graft from any post-ganglionic source i.e. spinal accessory to suprascapular nerve and 3x intercostals to the bicesp)
**Takes 2 years for recovery but only 50% have good recovery with elbow flexion
Which nerves injuries recover better?
Radial > median > ulnar;
Tibial >> peroneal
What is the rule of
The nerves that move muscles of a joint are innervated above that joint
What muscles are supplied by the anterior interosseous nerve?
Flex digitorum, FDP and PQ
What causes thenar atrophy alone with pain and paraesthesia?
Carpal tunnel syndrome
A patient is unable to make an O sign?
Anterior intersseous nerve syndrome means the patient makes a square pinch not an O sign. FPL, FDP to index and PQ are weak (usually due to inflammatory neuropathy). These patients have normal sensation.
What is the Benediction sign?
Complete median nerve injury as the patient cannot bend the index finder at all (no FDS). Often traumatic.
Is the nerve in continuity following a gunshot wound?
80% are; Get an USS to prove it!
What book should be used for peripheral nerve anatomy?
MRC. Aids to peripheral nerve book 4th ed
Why can a patient with an ulnar nerve injury make fist using the little and ring fingers?
Flexor digitorum superficialis is intact so the finger bends at the PIP
What does clawing tell you about the site of the ulnar nerve injury?
The most severe clawing occurs with the most distal injuries
How can ulnar nerve compression with cubital tunnel vs guyons canal be differentiated?
The dorsal cutaneous nerve comes off 6cm before the wrist so with Guyons canal they have retained sensation at the back of the hand
What is the differentiation between the Benediction sign in Median and Ulnar nerve?
In median nerve the patient cannot flex the first finger, In ulnar nerve they cannot extend the little and ring fingers
What diagnosis should you always think of in a patient with bilateral hand atrophy?
Motor neuron disease!
What happens to the ulnar nerve in Guyons canal?
It splits into a superficial palmar sensory branch and deep motor branch
What is Gilliatt-Sumner Hand?
Thenar and hypothenar atrophy (median and ulnar) caused by thoracic outlet syndrome. Rule out pancoast tumour. Most likely due to a cervical rib / band!
Most common cause of numbness in the ulnar 2 fingers?
C8 root compression (C7/T1 disc)
What is most efficacious operation for ulnar nerve at the elbow
Decompression, subcutaneous and submuscular transposition are all equally efficacious in recent prospective studies
Which nerve causes a) wrist drop and b) finger drop?
a) Radial nerve as the ext carpi radialis and ulnaris as both lost and b) PIN has radial deviation on wrist extension as extensor carpi radialis has already come off and no sensory cutaneous loss
What causes compression of PIN?
Arcade of Frohse
What nerve will be injured with a humeral fracture?
Radial nerve (note ulnar nerve is affected with a medial condylar fracture)
Shoulder pain and weakness in abduction and external rotation. Which nerve is affected?
Suprascapular nerve under the suprascapular ligament
What is the most common cause of a serratus anterior dysfunction?
Parsonage tuner syndrome causing winging of the scapula only. Takes up to 2 years to get better!
Which nerves can be affected with Parsonage Turner syndrome?
Long thoracic, suprascapular, axillary, AIN and PIN
How do benign nerve sheath tumours present?
Mass with no or little neurology
What is the indication for surgery on a benign peripheral nerve?
Pain, Neurology or Growth
What percentage of neurofibromas transform in patients with NF-1?
What is the prognosis of a malignant nerve sheath tumour?
50% 5 year mortality
What is meralgia paraesthetica?
Lateral cutaneous nerve of the thigh compression
How would you confirm the diagnosis of meralgia paraesthetica?
Tinel's sign at / above the inguinal ligament
What is the sight of entrapment for meralgia paraesthetica?
Do you get imaging for a foot drop?
Yes - MRI of the lumbar spine if L5 radiculopathy or knee if common peroneal nerve compression
How can common peroneal and deep peroneal nerve palsy be differentiated?
Both have a foot drop with intact tibitalis posterior resulting in inversion of the foot but the deep peroneal nerve palsy does not have the numbness on the lateral leg
What proportion of patients have the sciatic nerve passing through the piriformis muscle?
10% of the normal population
Where is the femoral nerve most likely compressed?
What deficit results from femoral nerve injury?
Quadriceps weakness +/- iliopsoas
What is tarsal tunnel syndrome?
Compression of the posterior tibial nerve under the flexor retinaculum (mostly due to oedema or tumour)
What branches are given off from the posterior tibial nerve at the ankle?
Medial and lateral plantar nerves
What nerve supplies supraspinatus?
What muscles would you test to distinguish L5 radiculopathy from common peroneal nerve palsy?
Tibialis posterior (ankle inversion)
Gluteus medius (hip abduction)
Hamstrings (Knee flexion)
What is reduced recruitment?
What is the cause of fibrillations and postiive sharp waves?
What is an F-wave?
Maximal nerve stimulation results in an antidromic AP that travels up to the spinal cord and then back down the nerve. Allows interrogation of the proximal part of the nerve. Normally the F-wave is generated 10% of the nerve fibres.
Why is the SNAP normal with radiculopathy?
As the DRG is distal to the region of compression with radiculopathy so the SNAP is normal
Weak leg with brisk reflexes and normal sensation. Where is the lesion?
What are the four parts of a peripheral nerve examination?
History - motor / sensory / pain
Physical - weakness / sensation / pain (provocative maneouvre e.g. tinel's and spurlings)
EMG - to localise and grade severity
Imaging - USS or MRI
What extra test would you get in a patient with a C5 nerve injury?
CXR for raised hemi-diaphragm
How do you examine C5?
Shake hand (look for atrophy)
Undress - cutaneous features / scars
Rhomboids - pull shoulders back
Shoulder abduction - supraspinatus (first 40 deg) and then deltoid
External rotation - infraspinatus
Cough - latissimus dorsi
Winging of scapula - serratus anterior
What is the main cause of isolated winged scapula?
How do you examine C6?
Elbow flexion - Biceps
Brachioradialis - pronated elbow flexion
What is the nerve supply to triceps?
C6,7,8 Radial nerve
What are the wrist pronators?
Pronator quadratus (C8)
Pronator terres (C6/7)
From median nerve
What is the nerve supply to the 3 wrist extensors?
What movement does the PIN do?
Extension of fingers at MCP and PIP
What nerve supplies flexion at the DIP joint?
Median nerve - anterior interosseous nerve (C8)
What serve supplies flexion at the PIP joint?
Median nerve (not anterior interosseous)
What is Froment's sign?
Test thumb abduction (Ulnar nerve supply)
What is Pemberton's sign?
Test for thoracic outlet syndrome; abduct arm and look to opposite side
What are the surgical options for peripheral nerve injuries?
When to operate on a peripheral nerve injury?
<3 days - clean laceration
< 3 weeks - blunt or ragged transection
>3 months - lesions with nerve in continuity e.g. gunshot wound injures the nerve due to shock wave and not transected in 80%
>1 year - salvage surgery
What is the usual time course for nerve recovery?
90% recover within 4 months
Where the different segments of the brachial plexus?
Nerve - neck
Trunk - above clavicle
Division - below clavicle
Cord - around the axillary artery
Why does a trapezius injury prevent shoulder abduction?
Stabilises the scapula
What is neurolysis?
Freeing up scar tissue i.e. 360 deg decompression
When do you do neurolysis?
When there is a neuroma in continuity and when the lesion conducts nerve action potentials across it
What should be done with a neuroma in continuity when there are no NAPs across it?
Resect the scar and do a primary repair if the ends come together without tension or graft if the ends do not come together
What nerve is injured during a posterior triangle cervical lymph node biopsy?
Spinal accessory nerve
Which muscles shrug the shoulder?
Which nerves cause winged scapula?
Dorsal scapula n
Spinal accessory n
Long thoracic n
Can a sural nerve be used to graft a radial nerve?
NO, sural nerve is much smaller. You have to do multiple cable grafts to repair it.
How do you repair a patient with Erbs palsy?
Sural nerve cable grafts to the upper trunk (only if post-ganglionic!)
What is a stinger?
C5/6 brachial plexus injury (neuropraxia) that lasts for a few seconds
What is neurotization?
Nerve transfer of an expendable working nerve to a more important non-functioning nerve
When do you do nerve transfers?
When there is a pre-ganglionic nerve injury so nerve grafts will not work
What is the goal of a nerve transfer?
Shoulder and elbow function (hand function does not repair!)
What nerve transfer can you do for a pre-ganglionic Erb's palsy?
Ulnar nerve branch to flex. carpi ulnaris and direct repair to the nerve going to the biceps or intercostal nerves can be used!
What nerve transfer can you do for a preganglionic Erb's palsy?
Distal accessory nerve branch (after trapezius is supplied) and connect to the suprascapular nerve
How fast do nerves repair?
1 inch a month (site of nerve injury to the muscle being innervated)
What does the suprascapular nerve supply?
Supraspinatus and infraspinatus
What muscles are supplied by the median nerve before the AIN comes off?
Which muscles are supplied by the median nerve in the hand?
What is clinical sign associated with AIN?
Patient cannot make an OK sign as the DIP in the finger and thumb cannot flex
How can AIN and median nerve injury be differentiated?
AIN injury allows PIP flexion but median nerve injury cannot. AIN has no sensory loss!
Where is the AIN given off?
6 cm below elbow
What is the main cause of an AIN injury?
How can you check there is no vascular injury associated with a brachial plexus injury?
What is the sensory branch from the ulnar nerve?
Dorsal cutaneous nerve (given off 6cm proximal to the wrist)
Does Guyon's canal ulnar nerve compression give numbness?
Not at the dorsum of the hand
What is Gilliat-Sumner hand?
Ulnar and median nerve loss - suggests lower trunk (C8/T1) caused by thoracic outlet syndrome or Pancoasts tumour
What is the difference between C8 palsy and Ulnar nerve palsy?
C8 affects little and whole of ring finger
C8 also affects all the flexors in the hand whilst ulnar just does ring and little finger flexion
Why is triceps normal in most radial nerve injuries?
Branches to triceps are given off high
What causes a wrist and finger drop?
Radial nerve injury at the spiral groove of the humerus (think saturday night palsy / humerus fracture etc)
What causes finger drop without wrist drop?
PIN palsy (wrist extension occurs in the radial direction only)
What nerve supplies ext. carpi ulnaris?
What are nascent units?
Reinnervation units on EMG
What causes suprascapular nerve palsy?
Compression of the suprascapular nerve under the suprascapular ligament
What nerves are affected by Parsonage-Turner?
What is the root supply to long thoracic nerve?
How do peripheral nerve tumours present?
Tap test causes tingling = BENIGN (schwannoma)
Weakness and lots of severe pain, rapid enlargement, NF-1 = MALIGNANT. These are high on PET with necrosis!
What lesions have a nerve going in and out?
Which peripheral nerve sheath tumours become malignant?
What is the 5y survival of a MPNST?
50% at 5 years
Where does the lateral femoral cutaneous nerve arise from?
Where is the lateral femoral cutaneous nerve in relation to the ASIS?
What examination test should be done for meralgia parasethetica?
Tinels sign medial to ASIS
Why the compressed nerve enlarged?
Pseudoneuroma due to injury
How can you distinguish common peroneal nerve palsy from L5 radiculopathy?
Peroneal nerve - pain from knee to foot and weak ankle extension in eversion and normal inversion negative SLR. Tinels at lateral knee
L5 - sciatica and foot drop with loss of inversion (ankle extension and inversion is tibialis posterior from Tibial nerve!)
What are the branches of the common peroneal nerve?
Deep to 1st web space, superficial to lateral leg and articular to knee joint
What muscle is retracted to cut the fibrous band at the peroneal tunnel?
What nerve is injured if peroneus longus function is normal?
superficial peroneal nerve palsy
What nerve causes toe flexion?
What nerve is injured if tibilais anterior function is normal?
Deep peroneal nerve
What differentiates a common peroneal nerve injury from a sciatic nerve?
Short head of biceps is lost with Sciatic nerve!
Where is short head of biceps femoris?
Lateral to the popliteal fossa
Where is the arcade of Frohse?
Between the two heads of supinator and causes PIN palsy
Where is osborne's ligament?
Roof of the cubital tunnel
What nerve supplies sensation to the medial leg?
How can you differentiate femoral nerve from L3 radiculopathy?
Test adduction (adductor longus)!
What nerve does the tarsal tunnel compress?
Where is the tarsal tunnel?
Behind the medial malleolus
What salvage procedure can be performed if a foot drop is not repairing after one year?
How do you know how distal to decompress the carpal tunnel?
Until you reach the fat pad!