Session 9 - Raised Intracranial Pressure

Question 1

What is the range for normal intracranial pressure?

Answer 1

5-15 mm Hg

Question 2

How is blood flow to the brain regulated in healthy individuals?

Answer 2

Autoregulation:

• vasoconstriction
• vasodilation

Chemo-regulation:
- vasodilation in response to low cerebral pH e.g. high pCO2

These can maintain ICP to a degree even in diseased states

Question 3

What are the signs and symptoms of raised intracranial pressure?

Answer 3

Headache
Vomiting 
CN VI palsy
Visual disturbances
Depression of conscious level
In infants, slowly increasing intracranial pressure may present as a slowly increasing head size.

Question 4

Describe the headache experienced by patients with raised intracranial pressure.

Answer 4

Generalised headache 
Worst on awakening in the morning (result of hypoventilation during sleep and increased venous pressure in the head when lying down)
May awaken patient from sleep
Aggravated by bending, stooping 
Aggravated by coughing or sneezing
Severity gradually progresses

Question 5

The nausea and vomiting experienced by patients with raised intracranial pressure will eventually progress to what?

Answer 5

Projectile vomiting

Question 6

What visual disturbances are experienced by patients with raised intracranial pressure?

Answer 6

Blurring
Obscurations - transient blindness upon bending or posture changes
Papilloedema in some patients
Retinal haemorrhages if the rise in ICP has been rapid

Question 7

Why do patients with raised intracranial pressure experience depression of conscious level?

Answer 7

Ischaemia of the reticular formation

Question 8

What are the three kinds of brain herniation?

Answer 8

Subfalcine herniation
Uncal herniation
Tonsillar herniation

Question 9

Which kind of brain herniation is the most common?

Answer 9

Subfalcine herniation

Question 10

What are the symptoms of a subfalcine herniation?

Answer 10

May be asymptomatic
Symptoms can include headache and contralateral leg weakness if anterior cerebral artery affected.
Midline shift on CT

Question 11

How is the brain displaced in an uncal herniation?

Answer 11

The uncut (medial part of the temporal lobe) is displaced across the tentorial opening.

Question 12

What are the symptoms of uncal herniation?

Answer 12

As the herniation progresses, the uncus puts pressure on the midbrain. This leads to
Ipsilateral oculomotor nerve (parasympathetic fibres) - ipsilateral dilated pupil
Compression of cerebral peduncle - contralateral leg weakness
Above signs may be false localising if the midbrain is pushed against the opposite side of the tentorium.
Decreased level of consciousness.

Question 13

What is a tonsillar herniation?

Answer 13

The cerebellar tonsils herniate through the foramen magnum.

Question 14

What are the symptoms of a tonsillar herniation?

Answer 14

Compression of medulla and upper spinal cord.
Brainstem affected - cardiac and respiratory dysfunction
Decreased level of consciousness

Question 15

What is Cushing’s reflex?

Answer 15

If raised ICP is untreated and continues to rise you get a triad of:

High BP
Bradycardia
Low respiratory rate - altered breathing pattern

Poor prognostic sign. If left untreated - death.

Question 16

Explain why Cushing’s reflex occurs.

Answer 16

Ischaemia at the medulla —> sympathetic activation —> rise in blood pressure and tachycardia —> baroreceptors react —> bradycardia

Ischaemia at pons/medulla at respiratory centres —> low respiratory rate

Question 17

What are the causes of raised intracranial pressure?

Answer 17

Increased cerebral blood volume
Cerebral oedema
Increased CSF
Expanding mass/space occupying lesion

Question 18

What are the possible causes of increased cerebral blood volume?

Answer 18

Venous outflow obstruction

Venous sinus thrombosis

Question 19

What are the possible causes of cerebral oedema?

Answer 19

Meningitis
Encephalitis
Diffuse head injury
Infarction

Question 20

What are the possibel causes of increased cerebrospinal fluid?

Answer 20

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

Question 21

What are the possible causes of space occupying lesions?

Answer 21

Abscess
Tumour
Haemorrhage/haematoma

Question 22

What is the most common cause of raised intracranial pressure?

Answer 22

Traumatic brain injury leading to epidural, subdural or subarachnoid haemorrhages
(Can also be caused by anticoagulants)

Question 23

How does severe meningitis encephalitis lead to raised intracranial pressure?

Answer 23

Can cause brain oedema acutely and venous outflow obstruction long term

Question 24

Describe the contents of normal cerebrospinal fluid.

Answer 24

Contains very little protein
Little immunoglobulin
Only one to five cells (leukocytes) per ml
Is clear and colourless

Question 25

Where is CSF produced?

Answer 25

Choroid plexus cell of the ventricles

Question 26

Describe the route CSF takes from the lateral ventricle’s choroid plexuses to the venous circulation.

Answer 26

Lateral ventricle’s choroid plexus —> lateral ventricles —> through interventricular foramina —> third ventricle —> through cerebral aqueduct —> fourth ventricle —> through lateral and median apertures —> subarachnoid space —> arachnoid villi of venous sinuses —> venous blood —> heart and lungs

Question 27

What is hydrocephalus?

Answer 27

Accumulation of CSF thought to be due to an imbalance between production and absorption of CSF with subsequent enlargement of brain ventricles. Affects 1 in 1000 births

Question 28

What is the difference between non-communicating/obstructive and communicating hydrocephalus?

Answer 28

Non-communicating/obstructive - CSF is obstructed within the ventricles or between the ventricles and the subarachnoid space Communicating - there is communication between the ventricles and the subarachnoid space. (Problem lies outside of the ventricular system)

Question 29

What are the causes of non-communicating hydrocephalus?

Answer 29

Most commonly due to aqueduct blockage. Can be congenital or acquired. Also due to tumours e.g. meningioma

Question 30

What are the causes of communicating hydrocephalus?

Answer 30

Due to reduced absorption of blockage of the venous drainage system. It may also be due to increased CSF production (e.g. choroid plexus papilloma) Mostly post-meningitis - bacterial, fungal, TB Subarachnoid haemorrhage Trauma Neoplastic infiltration of subarachnoid space

Question 31

What are the most common brain tumours in children?

Answer 31

Astrocytoma Medulloblastoma Tend to be found in the midline or posterior regions

Question 32

What are the most common brain tumours in adults?

Answer 32

Glioma Meningioma Metastases (from lung, breast, kidney)

Question 33

What is idiopathic intracranial hypertension?

Answer 33

Raised intracranial pressure without evidence of hydrocephalus or mass lesion. Investigations come back normal including imaging of the Brian. But patient has signs of raised ICP.

Question 34

Who is most commonly affected by idiopathic intracranial hypertension?

Answer 34

Usually affects obese young women after weight gain.

Question 35

What are treatment options for idiopathic intracranial hypertension?

Answer 35

Weight loss Medical management using drugs e.g. carbonic anhydrase inhibitors CSF drainage and shunts

Question 36

What treatment is used in raised ICP due to expanding mass?

Answer 36

Surgical resection e.g. craniotomy | Steroids of high value for brain tumours

Question 37

What treatment is used in raised ICP due to cerebral oedema?

Answer 37

Treat the cause Mannitol Hypertonic saline

Question 38

What treatment is used in raised ICP due to increased cerebral blood volume?

Answer 38

Anticoagulation | Rarely use stunting of venous sinuses

Question 39

What treatment is used to treat raised ICP due to increased CSF?

Answer 39

Shunts Tumour resection Use diuretics whilst awaiting intervention e.g. furosemide, carbonic anhydrase inhibitors