intracranial pressure Flashcards
monro-kellie hypothesis
the sum of volumes of brain, CSF and intracranial blood is constant
an increase is one must cause a decrease in one or both of the remaining two
limited capacity to accomodate change in the volume of the cranium
blood, cerebral tissue, and CSF are relatively incompressible
CSF containing spaces and skull foramina are the only places where this can be accomodated
compensation by reducing intracerebral CSF and blood volume are only ways body can regulate ICP
herniation in the brain
increasing pressure betweenadjacent intracranial compartments lead to displaceemnt of the softs tissues of the brain through anatomical or pathological openings
problem with brain herniation
cerebral tissue can be irreversibly damage if compressed, particularly against hard (bone) or sharp (base of skull, edges of flax cerebro/tenorium cerebelli
how to measure intercranial pressure
by measuring CSF
normal: 150ml within and around brain and spinal cord
CSF is produces in
choroid plexus
constantly circulating and being produced and reabsorbed
normal ICP
7-15 mm Hg in adults who are supine
pathological ICP
20 mm Hg
abnormal ICP
15 mm Hg
CSF flow obstruction leads to
hydrocephalus
too much CSF interferes with circulation and resorbtion
causes of CSF flow obstruction
SOL aqueduct stenosis anatomical malformations SAH - sub arachnoid haemorrhage post-meningitis
cerebral oedema caused by
traumatic brain injuury ischaemic stoke hypoxic/isschaemic encephalopathy post operative metabolic/ionic imbalancce
raised ICP is caused by
- spcae occuupying lesin
- CSF flow obstruction
- cerebral oedema
- increaased venous pressure, increased volume CSF, idiopathic
raised ICP symptoms and sgns
headahce vomitng unexplained seizures hypertension bradycardiiia papilloedema focal neurological signs altered conscious state
compensations for raised ICP
decrease CSF volume
decrease blood volume
paranchymal displacement
