PATHOLOGY- raised ICP Flashcards
does the brain behave like a fluid or solid?
both
what is the brain suspended in?
the CSF in the skull
what supports the brain?
the dura
What is hydrocephalus?
accumulation of excessive CSF in the brain
what types of hydrocephalus are there and describe them
NON COMMUNICATING:
-obstruction to flow of CSF occurs within ventricular system
COMMUNICATING:
-Obstruction of flow of CSF outside of ventricular system e.g. in subarach space or in the arachnoid granulations
whatwhat are the causes of hydrocephalus?
Obstruction to flow of CSF:
-inflammation
-pus
-tumours
Decrease resorption of CSF:
-post SAH
-meningitis
Overproduction of CSF:
-tumours of choroid plexus
-very rare!
how may hydrocephalus present differently before cranial sutures close?
Before cranial suture closer= cranial enlargement
how may hydrocephalus present differently after cranial sutures close?
After cranial sutures closed= expansion of ventricles and increase in ICP
presentation of increased ICP:
-N+V
-headache (worse in morning and straining)
-pupillary dysfunction +/- papilloedema
-changes in vision
-decrease level of consciousness
what is hydrocephalus ex vacuo
When the brain tissue around the ventricles shrinks due to Alzheimers, fronto temporal dementia or stroke
Not a real hydrocephalus
- the dilatation of ventricular system and compensatory increase in CSF volume secondary to loss of brain parenchyma
-ICP is normal
what conditions cause hydrocephalus ex vacuo
conditions that cause loss of brain parenchyma e.g. Alzheimers, fronto temporal dementia, infarct on one side
-Brain enlarges, some blood +/- CSF must escape to avoid rise in pressure
-a further increase in brain volume occurs and there is a rapid increase in ICP
why?
-if brain enlarges, some blood +/- CSF must escape to avoid rise in pressure
-once this process is exhausted, venous sinuses are flattened and there is little remaining CSF
-any further increase in brain volume results in rapid increase in ICP
examples of causes of raised ICP
-increase CSF (hydrocephalus)
-focal lesion in the brain (space occupying lesion)
-diffuse lesion in the brain (e.g. oedema)
-increased venous volume
-physiological (hypoxia, hypercapnia, pain)
what effects does raised ICP have on the brain?
-Intracranial shifts and herniations e.g. ‘coning’
-Midline shift
-Distortion and pressure on cranial nerves and vital neurological centres
-impaired blood flow
Cerebral perfusion pressure= MAP- ICP
give examples of brain herniations
-Subfalcine herniation
-Tentorial (and central) herniation
-Cerebellar
-Transcalvarial
Describe a Subfalcine herniation
Subfalcine herniation - unilateral/ asymmetric expansion of the cerebral hemisphere displaces the gyrus under the false cerebri
presentation of Subfalcine herniation
-can cause compression of anterior cerebral artery causing weakness in the contralateral leg
describe a Tentorial (and central) herniation
when the medial innermost aspect of the temporal lobe herniates over the tentorium cerebelli
presentation of Tentorial (and central) herniation
compression of ipsilateral CN III and can cause pupillary dilatation, impairment of ocular movements on the same side as the herniation
describe a cerebellar herniation
displacement of the cerebellar tonsils through the foramen magnum
why is a cerebella herniation life threatening?
-it compresses the brain stem and so the respiratory centres in the medulla oblangata
describe a transcalvarial herniation
-swollen brain herniates through any defect in the dura and skull
what are clinical signs of raised ICP?
-reduced level of consciousness
-papilloedema
-headache
-N+V
-neck stiffness
examples of space occupying lesions?
-Tumours
-Abscess
-Haematomas
-Localised brain swelling (e.g. swelling and oedema around cerebral infarct)
where do most brain tumours in children occur in relation to the tentorium cerebello?
70% occur below the tentorium cerebelli
