Raised ICP

Question 1

What is normal ICP?

Answer 1

7-15mmHg in the supine position

Question 2

What is Cerebral perfusion pressure (CPP)

Answer 2

Net pressure gradient causing cerebral blood flow to the brain
CPP= mean arterial pressure - ICP

Question 3

What are the causes of raised ICP?

Answer 3

Idiopathic intracranial hypertension
traumatic head injuries
infection e.g. meningitis
tumours
hydrocephalus

Question 4

What is Cushing’s triad?

Answer 4

Widening pulse pressure
bradycardia
irregular breathing

Question 5

Features of raised ICP?

Answer 5

Headache
vomiting
reduced levels of consciousness
papilloedema
Cushing’s triad

Question 6

Investigations for raised ICP?

Answer 6

Neuroimaging- CT/MRI
Invasive ICP monitoring

Question 7

What is invasive ICP monitoring?

Answer 7

Catheter placed into the lateral ventricles of the brain to monitor the pressure
May also be used to collect CSF samples and also to drain small amounts of CSF to reduce pressure

Question 8

What is the cut off for raised ICP to decide if further treatment is needed?

Answer 8

If pressure is greater than >20mmHg in invasive ICP monitoring then further treatment is needed

Question 9

Management of raised ICP?

Answer 9

Investigate and treat underlying cause
Head elevation to 30 degrees
IV mannitol may be used as an osmotic diuretic
controlled hyperventilation
removal of CSF

Question 10

How is CSF removed in raised ICP?

Answer 10

Drain from intraventricular monitor
repeated LP
ventriculoperitoneal shunt

Question 11

How does controlled hyperventilation improved raised ICP?

Answer 11

aim is to reduce pCO2 → vasoconstriction of the cerebral arteries → reduced ICP
leads to rapid, temporary lowering of ICP. However, caution needed as may reduce blood flow to already ischaemic parts of the brain

Question 12

What is idiopathic intracranial hypertension?

Answer 12

Disorder of increased intracranial pressure with a patient that is alert and orientated.

Classically seen in a overweight female

Question 13

RF for idiopathic intracranial hypertension?

Answer 13

Obesity
Female
pregnancy
drugs

Question 14

What drugs put you at risk for idiopathic intracranial hypertension?

Answer 14

COCP
Steroids
Tetracyclines
Vit A
Lithium

Question 15

Features of idiopathic intracranial hypertensio?

Answer 15

Headache
blurred vision
papilloedema
enlarged blind spot
pulse-synchrous tinnitus
may have sixth nerve palsy

Question 16

Management of idiopathic intracranial hypertension?

Answer 16

Weight loss

Diuretics e.g acetazolamide

topiramate

repeated LP

surgery- optic sheath decompression and fenestration may be needed to prevent damage to the optic nerve.

A lumboperitoneal or ventriculoperitoneal shunt may also be performed to reduce ICP

Question 17

What’s hydrocephalus?

Answer 17

Excessive volume of CSF within the ventricular system of the brain, caused by an imbalance between CSF production and absorption

Question 18

Presentation of hydrocephalus?

Answer 18

Headache-worse in the morning, when lying down and during Valsalva
N&V
Papilloedema
Coma (severe cases)
‘Sunsetting’ eyes (failure of upward gaze) in children

Question 19

How does hydrocephalus affect the fontanelles in children?

Answer 19

Skull sutures not fused, pathological rise in ICP–> increase head circumference–> open anterior fontanelle will bulge and become tense

Question 20

Why do children with hydrocephalus get ‘sunsetting gaze’

Answer 20

compression of the superior colliculus of the midbrain

Question 21

Categories of hydrocephalus?

Answer 21

Obstructive (non-communicating) hydrocephalus
Non-obstructive (communicating) hydrocephalus

Question 22

What is obstructive hydrocephalus?

Answer 22

Structural pathology blocking flow of cerebrospinal fluid

You see dilation of ventricular system superior to site of obstruction

Question 23

Cause of obstructive hydrocephalus?

Answer 23

Tumours
Acute haemorrhage (SAH)or intraventricular haemorrhage
developmental abnormalities

Question 24

What is non-obstructive hydrocephalus?

Answer 24

Due to an imbalance of CSF production absorption

Question 25

Causes of non-obstructive hydrocephalus?

Answer 25

Increased CSF production- choroid plexus tumour (very rare)
Failure of reabsorption at the arachnoid granulations (meningitis or post haemorrhagic)

Question 26

What is normal pressure hydrocephalus?

Answer 26

Unique form of non-obstructive hydrocephalus
Characterised by large ventricles but normal ICP

Question 27

What are the classic triad of symptoms in normal-pressure hydrocephalus?

Answer 27

Dementia
Incontinence
Disturbed gait

Question 28

Investigations in hydrocephalus?

Answer 28

CT Head used as a first line imaging investigation
MRI may be used to investigate hydrocephalus in more detail
LP- diagnostic and therapeutic

Question 29

Treatment for hydrocephalus?

Answer 29

External ventricular drain–> acute, severe hydrocephalus–> inserted into the R lateral ventricle and drains into bad at bedside

Ventriculoperitoneal shunt (VPS)–> long term CSF diversion technique–> drains CSF from the ventricles to the peritoneum

Obstructive hydrocephalus–> may have to surgically treat the obstructing pathology

Question 30

When can you NOT use an LP in hydrocephalus?

Answer 30

OBSTRUCTIVE hydrocephalus
Difference in brain and spinal pressures induced by drainage of CSF will cause brain herniation