Raised ICP and Hydrocephalus Flashcards
what 3 intracranial components make up the monroe-kellie doctrine?
brain
blood
CSF
what does the monroe-kellie doctrine say about the 3 intracranial components and their relationship to ICP?
all 3 components have pressure exerted on them
if pressure exerted in any of the 3 increase or if a 4th component introduced (tumour, bleed etc) then this can raise ICP
what physiological functions can increase ICP?
coughing / sneezing
going to toilet
(can also be elicited by valsalva maneouvers)
what is normal ICP at rest?
7-15mmHg
ICP can be negative - true or false?
true - if patient is in vertical position or under general anaesthetic
also often negative in babies
how do we immediately compensate for acute rise in ICP?
CSF pushed out of foramen magnum
decreased blood volume to the brain
roughly how much CSF is made per day?
around 1 pint
how is the cerebral perfusion pressure calculated?
mean arterial blood pressure (MAP) - ICP = CPP
cerebral perfusion pressure is the same as cerebral blood flow - true or false?
false
CPP = net pressure gradient causing cerebral blood flow to brain
(narrow limit as too little blood means ischaemia and too much raises ICP)
cushings triad is the opposite of a shock response from the body - what symptoms are experienced?
hypertension
bradycardia
irregular breathing
what is meant by the term “autoregulation” of cerebral blood flow?
means that cerebral blood flow remains constant over a variety of blood pressures
when would autoregulation of cerebral blood flow be lost?
post brain injury
how can ICP be decreased by patient themselves?
hyperventilation - decreases CO2 which decreases BP which causes vasoconstriction of blood vessels in body which decreases cerebral blood flow which decreases ICP
what non-CSF related causes are there for raised ICP?
mass - tumour, infarct
brain swelling - ischaemia, encephalopathy
increased central venous pressure - venous sinus thrombosis, heart failure
what problems with CSF flow can lead to raised ICP?
obstruction - masses (colloid cyst, tumour at midbrain), chiari (cerebellar tonsils herniate through foramen magnum)
increased production (choroid plexus papilloma)
decreased absorption (subarachnoid haemorrhage, after meningitis)
what are the early signs of a raised ICP?
decreased conscious level
headache
pupil dysfunction / change in vision
nausea and vomiting (due to midbrain distortion)
what late signs present in raised ICP?
coma fixed dilated pupil hemiplegia cushings triad hyperthermia increased urinary output
what are the aims of intervention in raised ICP?
maintain cerebral perfusion pressure
prevent ischaemia
how should blood flow to head be promoted through intervention?
ensure head in midline / neutral position
loosen any collars / jewellery
put head of bed between 30-45 degrees to maximise blood flow
how should spikes in ICP be avoided through intervention?
decrease any environmental stimuli that could cause patient to gag/cough/sneeze etc
why is it important to intervene when patients GCS can still be at 15?
rapid decompensation of brain after prolonged period of compensating
if any suspicion patient is about to decompensate, then they require surgery before herniation of brain
what medicinal treatments can be used in raised ICP?
diuretics (mannitol, hypetonic saline, furosemide)
barbiturate coma (phenobarbitone used to subdue all but basic brain functions)
anti-epileptic drugs sometimes used
what is the difference between a communicating and non-communicating hydrocephalus?
communicating = all ventricles dilated
non communicating = not all ventricles dilated (depends on point of obstruction - usually between 3rd or 4th ventricle causing triventricular enlargement)
what is meant by the buzzword “sun-setting” eyes?
compression of midbrain in hydrocephalus causes problems moving eyes upwards
how do infants with hydrocephalus usually look in western world?
flat and broad face (not usually the very large forehead)
who normally gets normal pressure hydrocephalus and why?
elderly - idiopathic
what is in the hakims triad of normal pressure hydrocephalus?
abnormal gait (wide based shuffle)
urinary incontinence
dementia (usually mild)
what are other differentials of normal pressure hydrocephalus?
other forms of dementia cervical myelopathy all urinary problems parkinsons depression
why are dilated ventricles in the context of brain atrophy not considered to be hydrocephalus?
ventricles are dilating relative to the loss of brain tissue, not because of increased amount of CSF = ventriculomegaly
how should normal pressure hydrocephalus be investigated?
lumbar puncture (see if taking off 30mls of CSF makes any difference to symptoms)
lumbar drain test (72 hours of draining CSF)
lumbar infusion study
what should you complete before and after a lumbar train test to check if it has made difference to patient?
MMSE or other cognitive test
get up and go test
lumbar drain test should improve these, especially gait
how is hydrocephalus treated?
ventriculoperitoneal shunt
ventricles dilate in idiopathic intracranial hypertension - true or false?
false - no dilation of ventricles, if they are dilated it is not IIH
who usually gets IIH?
women of childbearing age (hormones)
often overweight western population
what are the usual presenting signs and symptoms of IIH?
headache (worse above eyes, patient doesnt want to look upwards)
double vision/blurring/field defects/papilloedema
pulsatile tinnitus
radiculopathy of arms if pressure reaches cervical spinal cord
what treatments are recommended for IIH?
weight loss
bariatric surgery
carbonic anhydrase inhibitors (acetazolomide, topiramate)
diuretics
shunt
interventional radiology to stent stenotic veins
what investigations are used in IIH?
LP - pressure can be grossly enlarged (45-50mmHg)
CT/MRI of head
CTV to check for venous stenosis
fundoscopy / ophthalmology review
