Raised Intracranial Pressure

Question 1

What is contained in the intracranial space?

Answer 1

Brain

Dura mater

Blood

CSF

Question 2

Is there more arterial blood or venous blood in the intracranial space?

Answer 2

Venous blood

Question 3

What is intracranial pressure?

Answer 3

Refers to pressure within the intracranial space

Question 4

What is normal intracranial pressure?

Answer 4

5-15 mmHg

Question 5

How is intracranial pressure measured?

Answer 5

Lumbar puncture with a manometer, this is a tube which CSF runs up in, measure its height

Question 6

How is intracranial pressure regulated?

Answer 6

Regulation of blood flow to the brain by

• autoregulation
• chemoregulation

Question 7

What is autoregulation in terms of regulating intracranial pressure?

Answer 7

Vasoconstriction and vasodilation

Question 8

What is chemoregulation in terms of regulating intracranial pressure?

Answer 8

Vasodilation in response to low cerebral pH, high pCO2

Question 9

How is increasing intracranial pressure regulated?

Answer 9

Vasoconstriction to reduce venous blood volume

Reduced volume of CSF

Eventually cannot do this any further

Question 10

How does brain injury cause raised intracranial pressure?

Answer 10

Reduced arterial blood supply to brain cells
Reduced delivery of oxygen to brain cells
Reduced aerobic metabolism
Reduced ATP
Reduced function of Na+ K+ ATPase
Increased concentration of sodium ions in the brain cells
Water moves into the brain cells by osmosis
Oedema of brain cells
Further compression of arteries supplying the brain

Question 11

What are the signs and symptoms of raised intracranial pressure?

Answer 11

Headache

Vomiting

Visual disturbances, CN6 palsy

Depression of conscious level

In infants, may present as slowly increasing head size

Question 12

What are the characteristics of the headache with raised intracranial pressure?

Answer 12

Generalised ache

May wake the patient up from sleep

Worst when wake up in the morning
Aggravated by bending, stooping
Aggravated by coughing, sneezing

Severity gradually progresses

Question 13

Why do the aggravating factors of a headache with raised intracranial pressure make it worse?

Answer 13

Increased venous blood volume in the intracranial space, further raising the intracranial pressure

Question 14

Why is there vomiting with raised intracranial pressure?

Answer 14

Ischaemia and hypoxia of vomiting centre in the brain

Question 15

How does the vomiting change with the duration of the raised intracranial pressure?

Answer 15

Starts off as nausea, progresses to vomiting, then to projectile vomiting

Question 16

What are the visual disturbances with raised intracranial pressure?

Answer 16

Blurring

Obscurations

Papilloedema

Retinal haemorrhages

Question 17

What causes the visual disturbances with raised intracranial pressure?

Answer 17

Compression of the CN2 optic nerve

Because it is an extension of the brain so it surrounded by dura and CSF

Question 18

What does the optic disc look like on fundoscopy with raised intracranial pressure?

Answer 18

Enlarged

Blurred outline

Question 19

What does the retina look like on fundoscopy with raised intracranial pressure?

Answer 19

Cannot see blood vessels on retina

Question 20

Retinal haemorrhages tend to occur with raised intracranial pressure that happened…

Answer 20

Rapidly

Question 21

Why does a CN6 abducens nerve palsy occur with raised intracranial pressure?

Answer 21

CN6 abducens nerve runs closely to the pons and the skull, easily compressed by raised intracranial pressure

Question 22

What are the signs and symptoms of a CN6 abducens nerve palsy?

Answer 22

Patient’s eye is adducted due to unopposed pull of the medial rectus muscle

Patient cannot abduct their eye due to loss of innervation to lateral rectus muscle

Question 23

Why is there a depression in consciousness level with raised intracranial pressure?

Answer 23

Due to effects of ischaemia on raised intracranial pressure

Question 24

What are the complications of raised intracranial pressure?

Answer 24

Herniation syndromes

Cushing’s reflex

Question 25

What are the different types of herniation syndromes? Which is the most common?

Answer 25

Subfalcine herniation - most common Uncal herniation Tonsillar herniation

Question 26

What is a subfalcine herniation?

Answer 26

Refers to the herniation of the brain under the falx cerebri

Question 27

What are the signs and symptoms of a subfalcine herniation?

Answer 27

Asymptomatic Contralateral leg weakness if anterior cerebral artery is compressed

Question 28

What does a subfalcine herniation look like on a CT head scan?

Answer 28

Midline shift

Question 29

What is an uncal herniation?

Answer 29

Uncus of temporal lobe herniates through the opening of the tentorium cerebelli Uncus compresses the midbrain

Question 30

What are the signs or symptoms of uncal herniation?

Answer 30

Dilated pupil Contralateral weakness Decreased level of consciousness

Question 31

Why does uncal herniation cause a dilated pupil?

Answer 31

Compression of CN3 oculomotor nerve | Loss of parasympathetic innervation to the constrictor pupillae muscle on same side

Question 32

Why does uncal herniation cause contralateral weakness?

Answer 32

Compression of cerebral peduncles | Which contain sensory and motor fibres running between the cerebral hemispheres and the pons

Question 33

Why does uncal herniation cause decreases level of consciousness?

Answer 33

Compression of reticular formation

Question 34

What is a tonsillar herniation?

Answer 34

Cerebellar tonsils herniates through the foramen magnum

Question 35

What are the signs and symptoms of a tonsillar herniation?

Answer 35

Decreased level of consciousness Cardiovascular and respiratory dysfunction

Question 36

Why does a tonsillar herniation cause decreased level of consciousness?

Answer 36

Compresses the reticular formation

Question 37

Why does a tonsillar herniation cause cardiovascular and respiratory dysfunction?

Answer 37

Compresses the medulla which contains the cardiovascular and respiratory control centres

Question 38

What is Cushing’s reflex?

Answer 38

Physiological nervous system response to continuous raised intracranial pressure - high blood pressure - bradycardia - low respiratory rate

Question 39

What causes high blood pressure and bradycardia in Cushing’s reflex?

Answer 39

Ischaemia of medulla results in activation of sympathetic nervous system Which increases blood pressure and causes tachycardia Baroreceptors react to this and stimulate bradycardia

Question 40

What causes low respiratory rate in Cushing’s reflex?

Answer 40

Ischaemia of pons and medulla, which contain the respiratory centres, gives low respiratory rate

Question 41

What are the causes of raised intracranial pressure?

Answer 41

Cerebral oedema Increased cerebral blood volume Increased CSF Expanding mass

Question 42

What are the causes of cerebral oedema?

Answer 42

Ischaemic stroke Meningitis Encephalitis Diffuse head injury

Question 43

What are the causes of increased cerebral blood volume?

Answer 43

Venous outflow obstruction | -venous sinus thrombosis

Question 44

What are the causes of increased CSF?

Answer 44

Impaired absorption - hydrocephalus - benign intracranial hypertension Excessive secretion -choroid plexus papilloma

Question 45

What are the causes of an expanding mass in the intracranial space?

Answer 45

Abscess Tumour Haemorrhage, haematoma

Question 46

What is hydrocephalus?

Answer 46

Accumulation of CSF

Question 47

What causes hydrocephalus?

Answer 47

Imbalance between production and absorption of CSF | More production or less absorption

Question 48

What are the types of hydrocephalus?

Answer 48

Non-communicating Communicating

Question 49

What is non-communicating hydrocephalus?

Answer 49

CSF is obstructed within the ventricles | Or between the ventricles and the sub-arachnoid space

Question 50

What are the causes of non-communicating hydrocephalus? Which is the most common cause?

Answer 50

Blockage of aqueduct Can be congenital or acquired Most common cause Tumours compressing the ventricular system

Question 51

What does non-communicating hydrocephalus look like on a CT scan?

Answer 51

Large third ventricle, small fourth ventricle

Question 52

What is communicating hydrocephalus?

Answer 52

Communication between the ventricles and the subarachnoid space

Question 53

What are the causes of communicating hydrocephalus? Which is the most common

Answer 53

Choroid plexus papilloma Post-meningitis - most common Sub-arachnoid haemorrhage Trauma Neoplastic infiltration of subarachnoid space -all give blockage of arachnoid granulation

Question 54

What does non-communicating hydrocephalus look like on a CT scan?

Answer 54

Whole ventricular system is enlarged

Question 55

What are the most common ages with brain tumours?

Answer 55

Children Late middle age

Question 56

What are the most common types of brain tumours in children?

Answer 56

Astrocytomas Medullablastomas

Question 57

What parts of the brain are brain tumours in children most common in?

Answer 57

Midline Posterior region

Question 58

What are the most common types of brain tumours in middle-aged people?

Answer 58

Metastases from other types of tumours e.g. breast, lung, kidney cancer

Question 59

What are the most common types of primary brain tumours in middle-aged people?

Answer 59

Gliomas Meningiomas

Question 60

What is idiopathic intracranial hypertension?

Answer 60

Raised intracranial pressure but no pathology

Question 61

What group of patients most commonly have idiopathic intracranial hypertension?

Answer 61

Obese women after weight gain

Question 62

How is idiopathic intracranial hypertension treated?

Answer 62

Weight loss Carbonic anhydrase inhibitor diuretics CSF drainage

Question 63

How can CSF be drained to treat idiopathic intracranial hypertension?

Answer 63

Therapeutic lumbar puncture Shunts

Question 64

How is raised intracranial pressure due to cerebral oedema treated?

Answer 64

Treat the underlying cause Give mannitol or hypertonic saline

Question 65

Why is mannitol or hypertonic saline given to treat raised intracranial pressure due to cerebral oedema?

Answer 65

Makes the plasma hyper-osmotic to CSF So water moves from the CSF to the plasma Reducing the volume of CSF

Question 66

How is raised intracranial pressure due to increased cerebral blood volume treated?

Answer 66

Anticoagulation for venous sinus thrombosis Or stunting of venous sinuses

Question 67

How is raised intracranial pressure due to increased CSF treated?

Answer 67

Shunts from the ventricles to the peritoneum Tumour resection Diuretics while waiting for other treatments e.g. carbonic anhydrase inhibitors

Question 68

How is raised intracranial pressure due to an expanding mass treated?

Answer 68

Surgical resection Draining abscess Craniotomy, surgically removing part of skull to relieve pressure