Raised ICP Flashcards
What is intracranial pressure?
The pressure within the skull and is the sum of pressure from brain tissue, blood volume and CSF
What is the Monroe-Kellie hypothesis?
Because the skull is a closed, non expandable compartment, an increase in one of the constituents of ICP is compensated for by a decrease in one of the other constituents
According to the Monroe-Kellie, what happens when ICP is increased?
Reduction in CSF production
Reduction of cerebral blood flow
Eventually herniation of brain tissue
What is the normal range of ICP?
5-15mmHg
What is cerebral perfusion pressure?
The net pressure gradient that supports cerebral blood flow
What is the equation for CPP?
CPP = MAP - ICP
According to the relationship between CPP and ICP, what happens when ICP increases?
Any increase in ICP will reduce the amount of blood flowing into the brain
What are causes of raised ICP?
Hydrocephalus
Head injury
Cerebral oedema
- Vasogenic: tumour, trauma, ischemia, infection
- Cytotoxic: hypoxia, hypercapnia, encephalopathy
- Interstitial: obstructive hydrocephalus
Dural sinus thrombosis
Metabolic: hypoxia and hypercapnia
SOL: tumours, abscess, haematoma
Idiopathic intracranial hypertension
What is the presentation of raised ICP?
Headache - worse in the morning, wakes patient from sleep, worse lying down, bending and coughing
Drowsiness
Nausea, vomiting
Malaise
Focal neurological symptoms
Visual - peripheral field loss, reduced acuity, pupil constriction then dilation, swollen disc (papilloedema)
Cushing’s response
What is Cushing’s response?
A physiological response to try and maintain CPP and prevent cerebral ischaemia
Hypertension, bradycardia, irregular breathing
Increase in MAP will try and improve the gradient for cerebral blood flow that was reduced by increase ICP
What investigations are done in raised ICP?
Bloods: FBC, U&Es, LFT, glucose, coagulation, culture, ABG
CT head
LP is no signs of SOL and deemed safe to do so (aim is to measure opening pressure)
What is the acute management of raised ICP?
ABCDE
Elevate head 30-40 degrees
What is the management of raised ICP that aims to reduce ICP?
Mannitol
Hypertonic saline
Intubate and hyperventilate (reduces PCO2, cause cerebral vasoconstriction and reduce ICP)
What is the management of raised ICP that aims to prevent cerebral oedema?
Dexamethasone
What is the surgical intervention for raised ICP?
Burr-hole
Craniotomy
Removal of SOL
What are the consequences of raised ICP?
Ischaemia and hypoxia
Brain herniation
What are the 4 types of brain herniation?
Subfalcine (cingulate)
Uncal (tentorial)
Tonsillar
Transcalvarial
What is a subfalcine herniation?
Herniation of frontal lobe under the falx cerebri
Will most commonly produce lower limb weakness
What is an uncle herniation?
Herniation of the temporal lobe under the falx cerebelli due to lateral mass pushing the brain medially
First sign will be ipsilateral 3rd nerve palsy
What is a tonsillar herniation?
Herniation of the cerebellar tonsils through the foramen magnum
Presents with ataxia, 6th nerve palsy and positive Babinski
Potentially life threatening as will result in brainstem compression
What is a transcalvarial herniation?
Herniation of the brain through defects in the dura and skull
What is idiopathic intracranial hypertension?
A diagnosis of exclusion made in patients who present with symptoms suggestive of an intracranial mass but no mass is found
Who is idiopathic intracranial hypertension more common in?
Young obese females, especially those with PCOS
What is the presentation of idiopathic intracranial hypertension?
ICP headache with nausea and vomiting, diurnal variation
Pulsatile tinnitus
Visual changes - blurred vision, double vision (6th nerve palsy), enlarged blind spot, swollen disc (papilloedema)
How is diagnosis of idiopathic intracranial hypertension made?
All standard investigations negative
LP shows high opening pressure
What is the management for idiopathic intracranial hypertension?
Weight loss
Medication - acetazolamide (reduced CSF production), prednisolone, loop diuretics
Surgical - LP shunt if drugs don’t reverse papilloedema
What is the prognosis of idiopathic intracranial hypertension?
Often self limiting
Permanent vision loss only seen in 10%
