Raised ICP Flashcards
What is normal ICP?
7-15mmHg in the supine position
What is Cerebral perfusion pressure (CPP)
Net pressure gradient causing cerebral blood flow to the brain
CPP= mean arterial pressure - ICP
What are the causes of raised ICP?
Idiopathic intracranial hypertension
traumatic head injuries
infection e.g. meningitis
tumours
hydrocephalus
What is Cushing’s triad?
Widening pulse pressure
bradycardia
irregular breathing
Features of raised ICP?
Headache
vomiting
reduced levels of consciousness
papilloedema
Cushing’s triad
Investigations for raised ICP?
Neuroimaging- CT/MRI
Invasive ICP monitoring
What is invasive ICP monitoring?
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
What is the cut off for raised ICP to decide if further treatment is needed?
If pressure is greater than >20mmHg in invasive ICP monitoring then further treatment is needed
Management of raised ICP?
Investigate and treat underlying cause
Head elevation to 30 degrees
IV mannitol may be used as an osmotic diuretic
controlled hyperventilation
removal of CSF
How is CSF removed in raised ICP?
Drain from intraventricular monitor
repeated LP
ventriculoperitoneal shunt
How does controlled hyperventilation improved raised ICP?
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
What is idiopathic intracranial hypertension?
Disorder of increased intracranial pressure with a patient that is alert and orientated.
Classically seen in a overweight female
RF for idiopathic intracranial hypertension?
Obesity
Female
pregnancy
drugs
What drugs put you at risk for idiopathic intracranial hypertension?
COCP
Steroids
Tetracyclines
Vit A
Lithium
Features of idiopathic intracranial hypertensio?
Headache
blurred vision
papilloedema
enlarged blind spot
pulse-synchrous tinnitus
may have sixth nerve palsy
Management of idiopathic intracranial hypertension?
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
What’s hydrocephalus?
Excessive volume of CSF within the ventricular system of the brain, caused by an imbalance between CSF production and absorption
Presentation of hydrocephalus?
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
How does hydrocephalus affect the fontanelles in children?
Skull sutures not fused, pathological rise in ICP–> increase head circumference–> open anterior fontanelle will bulge and become tense
Why do children with hydrocephalus get ‘sunsetting gaze’
compression of the superior colliculus of the midbrain
Categories of hydrocephalus?
Obstructive (non-communicating) hydrocephalus
Non-obstructive (communicating) hydrocephalus
What is obstructive hydrocephalus?
Structural pathology blocking flow of cerebrospinal fluid
You see dilation of ventricular system superior to site of obstruction
Cause of obstructive hydrocephalus?
Tumours
Acute haemorrhage (SAH)or intraventricular haemorrhage
developmental abnormalities
What is non-obstructive hydrocephalus?
Due to an imbalance of CSF production absorption
Causes of non-obstructive hydrocephalus?
Increased CSF production- choroid plexus tumour (very rare)
Failure of reabsorption at the arachnoid granulations (meningitis or post haemorrhagic)
What is normal pressure hydrocephalus?
Unique form of non-obstructive hydrocephalus
Characterised by large ventricles but normal ICP
What are the classic triad of symptoms in normal-pressure hydrocephalus?
Dementia
Incontinence
Disturbed gait
Investigations in hydrocephalus?
CT Head used as a first line imaging investigation
MRI may be used to investigate hydrocephalus in more detail
LP- diagnostic and therapeutic
Treatment for hydrocephalus?
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
When can you NOT use an LP in hydrocephalus?
OBSTRUCTIVE hydrocephalus
Difference in brain and spinal pressures induced by drainage of CSF will cause brain herniation
