13. Raised Intracranial Pressure

Question 1

What is normal intracranial pressure?

Answer 1

5-15 mmHg or 7-20cm H2O.

Question 2

What are the 2 ways that blood flow to the brain can be regulated to help regulate ICP, even in disease states?

Answer 2

Autoregulation - vasoconstriction and vasodilation.

Chemo-regulation - vasodilation in response to low cerebral pH eg high CO2.

Question 3

If there is a mass growing in the brain, what occupants of the intracranial space decrease to compensate for the raised ICP?

Answer 3

Venous volume and CSF.

Question 4

Describe the pathophysiology of brain cell injury when compressed by a tumour

Answer 4

Compression results in reduction of blood supply to the brain cells, cells can no longer make ATP, so no Na2+/K+ pump working, water accumulates in the cell due to osmosis, and so this leads to cytotoxic cellular oedema (cell bursts). There is then further swelling and compression.

Question 5

Describe the type of headache experienced by patients with raised ICP.

Answer 5

Generalised ache, worst on awakening in the morning, may awaken the patient. Aggravated by bending, stooping, coughing or sneezing and severity progresses gradually.

Question 6

Describe the type of vomiting experienced by patients with raised ICP.

Answer 6

Nausea and vomiting progressing to projectile vomiting.

Question 7

Describe the type of visual disturbances experiences by patients with raised ICP.

Answer 7

Blurring, obscurations including transient blindness upon bending or posture changes, papilloedema in some patients and retinal haemorrhages if the rise in ICP has been rapid.

Question 8

Where is the tumour likely to be if it causes a CNVI palsy?

Answer 8

Can be anywhere in the brain, as results from the brain being pushed against the skull due to raised ICP.

Question 9

What symptoms can occur in a subfalcine herniation?

Answer 9

May be asymptomatic, but can cause headache and contralateral leg weakness if the anterior cerebral artery is affected.

Question 10

What symptoms can occur in an uncal herniation?

Answer 10

Pressure on the midbrain as the herniation progresses leads to ipsilateral dilated pupil, contralateral leg weakness and decreased level of consciousness.

Question 11

What symptoms can occur in a tonsillar herniation?

Answer 11

Brainstem affected so cardiac and respiratory dysfunction and decreased level of consciousness.

Question 12

What is a subfalcine herniation?

Answer 12

Herniation of the midline brain against the falx cerebri.

Question 13

What is an uncal herniation?

Answer 13

Herniation of the uncus (medial temporal lobe) across the tentorial opening.

Question 14

What is a tonsillar herniation?

Answer 14

Herniation fo the cerebellar tonsils through the foramen magnum.

Question 15

What is Cushing’s reflex? What is the pathophysiology behind it?

Answer 15

A train of hypertension, bradycardia and low respiratory rate (altered breathing pattern). If untreated, leads to death.
Raised ICP, ischaemia at medulla, sympathetic activation, rise in blood pressure and tachycardia, baroreceptor reaction leading to bradycardia.
Raised ICP, ischaemia of the pons/medulla at the respiratory centres, leads to low respiratory rate.

Question 16

Name a cause of increased cerebral blood volume leading to raised ICP.

Answer 16

Venous outflow obstruction.

Venous sinus thrombosis.

Question 17

Name 2 causes of increased cerebral oedema leading to raised ICP.

Answer 17

Meningitis.
Encephalitis.
Diffuse head injury.
Infarction.

Question 18

Name a cause of increased CSF leading to raised ICP.

Answer 18

Impaired absorption eg hydrocephalus or benign intracranial hypertension.
Excessive secretion eg choroid plexus papilloma.

Question 19

Name a space occupying lesion leading to raised ICP.

Answer 19

Abscess.
Tumour.
Haemorrhage/haematoma.

Question 20

Changes in the components of CSF can be useful in diagnosis of disease processes. What are the normal components?

Answer 20

Clear, colourless, contains very little protein (15-45 mg/dL), little immunoglobulin and one 1-5 leukocytes per ml.

Question 21

What is hydrocephalus?

Answer 21

Accumulation of CSF due to an imbalance between production and absorption of CSF with subsequent enlargement of brain ventricles.

Question 22

What is non-communicating/obstructive hydrocephalus?

Answer 22

CSF is obstructed within the ventricles or between the ventricles and subarachnoid space, most commonly due to aqueduct blockade.

Question 23

What is communicating hydrocephalus?

Answer 23

There is communication between the ventricles and subarachnoid space, so the problem lies outside the ventricular system. Is due to reduced absorption or blockage of the venous drainage system, and may also be due to increased CSF production.

Question 24

What can non-communicating/obstructive hydrocephalus due to?

Answer 24

Congenital, squired or due to tumours eg meningioma.

Question 25

What can communicating hydrocephalus be due to?

Answer 25

Mostly post-meningitis (bacterial, fungal or TB), but can be due to subarachnoid haemorrhage, trauma, neoplastic infiltration of subarachnoid space, and choroid plexus papilloma.

Question 26

What are the two most common brain tumours in children and what cells do they develop from?

Answer 26

Astrocytomas - astrocytes.

Medulloblstomas - neuroectodermal cells.

Question 27

Where do brain tumours tend to occur?

Answer 27

Midline or posterior region.

Question 28

What are the 3 most common brain tumours in adults?

Answer 28

Metastases - from the lungs, breast and kidneys.
Gliomas.
Meningiomas.

Question 29

What is idiopathic intracranial hypertension?

Answer 29

Raised intracranial pressure without evidence of hydrocephalus or mass lesion.

Question 30

Who does idiopathic intracranial hypertension tend to occur in?

Answer 30

Obese young women after weight gain.

Question 31

Name 2 treatment options for idiopathic intracranial hypertension.

Answer 31

Weight loss.
Medical management eg carbonic anhydrase inhibitors.
CSF drainage (therapeutic lumbar puncture) and shunts.

Question 32

How would you treat raised ICP caused by increased cerebral blood volume?

Answer 32

Anticoagulation.

Tenting of venous sinuses.

Question 33

How would you treat raised ICP caused by cerebral oedema?

Answer 33

Treat the cause.
Mannitol - osmotic agent.
Hypertonic saline.

Question 34

How would you treat raised ICP caused by increased CSF?

Answer 34

Peritoneal shunts.
Tumour resection.
Use diuretics whilst awaiting intervention eg furosemide, carbonic anhydrase inhibitor.

Question 35

How would you treat raised ICP caused by a space occupying lesion?

Answer 35

Surgical resection eg craniotomy.

Steroids.