Intracranial Pressure and Hydrocephalus Flashcards
what is intracranial pressure
pressure exerted by the cranium on the brain tissue, CSF and intracranial circulating blood volume
what is the monroe- kellie- doctrine
three components of intracranial pressure (brain tissue, CSF and circulating intracranial blood), have pressure exerted on them, if you increase the volume of any of these components you will increase in the intracranial pressure
what is normal ICP
7-15mmHg
can be negative when in vertical position
higher than 15/16 probably abnormal
what are the compensatory mechanisms for an expanding mass
immediate- decrease in CSF volume by moving out of FM, decrease in blood by squeezing sinuses
delayed- decrease in ECF
what is the formula for cerebral perfusion pressure
MAP - ICP = CPP
what does a CPP below 20 usually mean
coma
what is cushings response/ triad
response to increased ICP opposite of shock result: -increased BP -irregular breathing -bradycardia
what are the theories of autoregulation of cerebral blood flow
pressure- vessel constriction/ dilatation
-metabolic- arterioles dilate in response to CO2/ lactic acid etc
CO2 is a potent dilator:
- increase CO2/ increased BP = vasodilation
- decreased CO2/ decreased BP= vasoconstriction
what are the common causes of raised ICP
mass effects- distort surrounding brain brain swelling (ischaemia, anoxia, metabolic, acute liver failure, encephalopathy, IIH, hypercarbia) - decreased cerebral perfusion but minimal tissue shift increase in central venous pressure (venous sinus thrombosis, HF, obstruction of jugular veins) problems with CSF flow (obstruction - masses, chiari syndrome), (increased production- choroid plexus papilloma), (decreased absorption- communicating hydrocephalus = SAH, meningitis, malignant meningeal disease)
what is chiari syndrome
a structural defect in the cerebellum, characterized by a downward displacement of one or both cerebellar tonsils through the foramen magnum
what are the early signs of raised ICP
decreased consciousness, HA, pupillary dysfunction +/- papilloedema, changes in vision, N&V
what are the later signs of raised ICP
coma, fixed dilates pupils, hemiplegia, bradycardia -> cushings triad, hyperthermia, increased urinary output
what is the intervention for raised ICP
goals= maintain CPP, prevent ischaemia and brain compression
- maintain head in midline to facilitate blood flow
- loosen tube ties, collars, jewellery etc
- head oh bed 30-45 degrees elevation
- avoid gagging/ coughing etc
- decrease environmental stimuli
- treat hyperthermia
- maintain fluid balance and normal electrolytes (watch urine output)
- maintain normocarbia (short term can hyperventilate patient to decrease CO2
what medical management exists for raised ICP
diuretics (mannitol, hypertonic saline, furosemide, urea)
barbiturate coma (later down the line, subdues the brain)
antiepileptics (prevent energy expendature that seizure would cause)
surgical decompression
other surgery- mass removal (abscesses have to removed within 24hrs) CSF diversion
what are the types of hydrocephalus
communicating (the dilatation of CSF is throughout the entire ventricular system) non communicating (obstruction occurs before the CSF floes out into the sagittal sinus, commonly at cerebral aqueduct)
can be congenital (aqueduct stenosis, choroid cyst, malformations, intraventricular haemorrhage)
or acquired
what is sunsetting eyes
unable to rise eyes due to high ICP
what type of hydrocephalus is caused by aqueductal stenosis
obstructive
what is normal pressure hydrocephalus
idiopathic disease of the eldery
get large ventricles (ventricular megaly) due to a smaller brain- will have large slyvian fissures
possibly due to decreased brain elasticity
what are the symptoms of normal pressure hydrocephalus
hakims triad- abnormal (wide based, shuffling gate), urinary incontinence (frontal dysfunction, loos inhibition), dementia
what are the differentials for normal pressure hydrocephalus
dementia, cervical myelopathy, urinary problems, parkinsons, depression
what investigations and treatment for normal pressure hydrocephalus
LP, lumbar drain test, lumbar infusion studies
Tx= VP shunt, median-low or low pressure valve
what is idiopathic intracranial hypertension and who gets it
raised ICP of unknown cause- must investigate fully, is a diagnosis of exclusion
mainly overweight women of child bearing age
mostly western civilisations
is there ventricular dilatation in IIH
no- if they have this then not IIH, will be hydrocephalus due to another cause
what are the symptoms of IIH
HA (v severe), double vision, visual blurring, tinnitus (usually pulsatile), radicular pain, papilloedema -> 25% have severe/ permanent visual loss
what are the theories of causes of IIH
CSF imbalance, hormonal (oestrogen), venous pressure (transverse/ sigmoid sinus stenosis)
what is the treatment for IIH
weight loss,
possible bariatric surgery,
carbonanhydrase inhibitors (acetazolamide, topiramate),
diuretics,
CSF diversion (LP or VP shunt),
interventional radiology (intracranial venous sinus plasty, intracranial venous sinus stenting),
ONSF (optic nerve sheath fenestration- purely to save vision, decreases pressure on nerves)
what differential for IIH
any other type of HA
any other reason for ICP
cervical radiculopahty
what investigations for IIH
LP
CT/ MR head
CTV/ MRV (look at veins and for stenosis)
fundoscopy +/ ophthalmology review
