Raised intracranial pressure

Question 1

What compensatory mechanisms occur if there is an increase in the intracranial pressure

Answer 1

Decreased blood pressure

Decreased CSF volume

Spatial brain atrophy

Question 2

Describe the Monro-Kellie doctrine

Answer 2

Monro-Kellie doctrine - any increase in volume of one cranial constituent must be compensated by a decrease in volume of another

Cranial constituents - venous and arterial blood, CSF, brain

Question 3

How does the vasomotor tone of the cerebral arteries change depending on the cerebral perfusion pressure

Answer 3

Cerebral perfusion pressure is the mean arterial pressure minus the ICP

If there is an increased CPP, then there is vasoconstriction of the arteries

If there is a decreased CPP then there is vasodilation of arteries, though this cannot occur if there is a mass causing the low CPP

Question 4

What is Cushing’s triad

Answer 4

Hypertension

Bradycardia

Irregular breathing

Question 5

Why does Cushing’s triad occur and how does it occur

Answer 5

Cushing’s triad occurs when the CPP becomes too low

Low CPP is detected by baroreceptors which send sympathetic stimulation to increase HR and BP -> hypertension

Increased BP sensed by carotid and aortic baroreceptors which send PNS signals to decrease HR -> bradycardia

Irregular breathing caused by herniating brain squashing the brainstem

Question 6

Name some causes of raised intracranial pressure

Answer 6

Too much blood - raised arterial, raised venous, haemorrhage (subdural, extra-dural, subarachnoid, intraventricular, haemorrhagic stroke)

Too much CSF - hydrocephalus, congential, acquired (meningitis, trauma, haemorrhage, tumour)

Too much brain - cerebral oedema

Tumour

Abscess

Question 7

What are the causes of congenital hydrocephalus

Answer 7

Congenital obstruction to CSF flow - neural tube defects, aqueduct stenosis

Communicating hydrocephalus - increased CSF production or decreased CSF absorption

Question 8

What are the signs of congential hydrocephalus (seen in babies)

Answer 8

Sunsetting eyes

Enlarging head

Question 9

What are the types of cerebral oedema (what are the causes)

Answer 9

Vasogenic

Cytotoxic

Osmotic

Intersitial

Question 10

What are the types of ventricular shunts

Answer 10

Ventriculo-atrial shut - ventricles to right atrium

Ventriculo-peritoneal shunt - ventricles to peritoneum. Easier to place but more prone to infection

Question 11

What can be used to drain CSF from the brain

Answer 11

External ventricular drain - short-medium term drainage and pressure monitoring

Ventricular shunts

Question 12

What are the types of brain herniation

Answer 12

Tonsillar/cerebellar tonsillar/coning

Sub-falcine

Uncal/tentorial

Central downward

External herniation through an open skull

Question 13

What s a sub-flacine herniation

Answer 13

Herniation on same side as mass in brain

Cingulate gyrus pushed under free edge of falx cerebri causing ischaemia of frontal and parietal lobes and corpus callosum

Question 14

Why are uncal herniations commonly fatal

Answer 14

Uncal herniations are frequently fatal as the downward herniation stretches the penetrating arteries of the basilar artery which then rupture causing secondary haemorrhage - Duret haemorrhage

Duret haemorrhage - small lineal areas of bleeding in midbrain and upper pons caused by traumatic downward displacement of brainstem

Question 15

Name some signs and symptoms of brain herniation

Answer 15

High BP

Irregular or slow pulse

Headache

Weakness

Loss of consciousness

Loss of brainstem reflexes

Respiratory arrest

Cardiac arrest

Question 16

Name some early symptoms of RICP

Answer 16

Headache

Nausea and vomiting

Difficulty concentrating

Drowsiness

Confusion

Diplopia and papilloedema

Focal neurological signs

Seizures

Question 17

What is idiopathic intracranial hypertension

Answer 17

Idiopathic intracranial hypertension is benign intracranial hypertension

Usually occurs in obese, middle aged women

Improves with weight loss and BP control

Question 18

Why must a head CT/MRI always be done before a lumbar puncture

Answer 18

Head CT/MRI must be done to look for any intracranial tumours

A tumour causing RICP can push CSF down the spine and if a lumbar puncture is done and CSF is released from the spine, it can pull the pressure downwards and cause a brain herniation

Question 19

What is SCIWORA

Answer 19

Spinal cord injury without radiographic abnormality

Is injury to the spinal cord with symptoms but no radiological abnormalities

Question 20

What brain protection measures should be done if a patient presents with significant brain/head injury

Answer 20

Airway control and ventilation - oxygenation and ventilation

Circulatory support - maintain CPP

Sedation, analgesia and paralysis - prevent movement

Head up position - head at 15-30 degree angle to improve venous drainage

Temperature - metabolic demand increased at high temps

Anticonvulsants - prevent seizures

Nutrition and PPI - prevent Cushing’s ulcers

Question 21

What is the treatment of RICP

Answer 21

Mannitol/3% hypertonic saline - increase osmolality of blood to draw fluid out of brain

External ventricular drain

Decompressive craniectomy