Raised ICP & hydrocephalus Flashcards
What are the causes of a raised ICP?
As the brain and ventricles are enclosed by a rigid skull, they have a limited ability to accommodate additional volume. Additional volume (e.g. haematoma, tumour, excessive CSF) will therefore lead to a rise in intracranial pressure (ICP).
What is the normal ICP in adults
7-15 mmHg
What is the cerebral perfusion pressure?
The net pressure gradient causing cerebral blood flow to the brain
What is the equation for cerebral perfusion pressure?
CPP = mean arterial pressure – ICP
What are the signs of hydrocephalus?
Headaches, vomiting, reduced levels of consciousness, Papilledema,
What is the Cushing’s triad present in hydrocephalus?
Widening pulse pressure, Bradycardia, irregular breathing
What investigations are done for hydrocephalus?
CT/MRI
Invasive ICP monitoring
What are the management plans for hydrocephalus?
investigate and treat the underlying cause
head elevation to 30º
IV mannitol may be used as an osmotic diuretic
What are some of the ways to remove excess CSF in hydrocephalus?
Drain from intraventricular monitor (see above)
Repeated lumbar puncture (e.g. idiopathic intracranial hypertension)
Ventriculoperitoneal shunt (for hydrocephalus)
What is the pathway of CSF production?
Choroid plexus (lateral ventricles) → ventricular system → subarachnoid space (Magendie and Luschka) → venous system (arachnoid granulations)
Hydrocephalus can be broadly divided into two categories; what are they?
Obstructive (‘non-communicating’) hydrocephalus
Non-obstructive (‘communicating’) hydrocephalus
What is an Obstructive (‘non-communicating’) hydrocephalus?
Due to a structural pathology blocking the flow of CSF.
Dilatation of the ventricular system is seen superior to site of obstruction
What is an Non-obstructive (‘communicating’) hydrocephalus?
Non-obstructive hydrocephalus is due to an imbalance of CSF production and absorption.
What are the causes of Obstructive (‘non-communicating’) hydrocephalus?
Tumours, acute haemorrhage (e.g. subarachnoid haemorrhage or intraventricular haemorrhage) and developmental abnormalities (e.g. aqueduct stenosis).
What are the causes of Non-obstructive (‘communicating’) hydrocephalus?
Caused by an increased production of CSF (e.g. choroid plexus tumour (very rare)) or more commonly a failure of reabsorption at the arachnoid granulations (e.g. meningitis or post-haemorrhagic).
What is a Normal pressure hydrocephalus?
A unique form of non-obstructive hydrocephalus characterized by large ventricles but normal intracranial pressure.
What are the features of Normal pressure hydrocephalus?
Dementia, incontinence, and disturbed gait
What investigations are dine for hydrocephalus?
CT and MRI (Better detail)
Why should a lumbar puncture not be done in obstructive hydrocephalus?
The difference of cranial and spinal pressures induced by the drainage of CSF will cause brain herniation
When is a external ventricular drain (EVD) used in hydrocephalus?
Used in acute, severe hydrocephalus and is typically inserted into the right lateral ventricle and drains into a bag at the bedside
What are other treatments for hydrocephalus?
Surgery for obstructive Carbon anhydrase inhibitors (Acetazolamide, Topiramate) Diuretics to reduce BP CSF diversion LP- or VP-shunt
