Neuropathology 2 - Demyelination and Dementia Flashcards
the brain is viscoeleastic, what does this mean?
mechanically behaves like a fluid and a solid
what happens to CSF in raised ICP?
some blood +/- CSF must escape from cranium to avoid pressure rise
once this is exhausted, venous sinuses are flattened and there is little - no CSF
therefore any further increase in brain volume causes raised ICP
normal CSF volume?
120-150 ml
500ml made per day
CSF made in which ventricles?
lateral and 4th
describe CSF fluid?
clear no neutrophils very few lymphocytes very little protein some glucose no RBCs >lymphocytes = infection >neutrophils = infection/meningitis
what can cause hydrocephalus?
obstruction to flow (tumour, inflammation etc) decreased reabsorption (post SAH, meningitis etc) overproduction (choroid plexus tumour - v. rare)
non-communicating hydrocephalus?
obstruction to flow within ventricular system
communicating hydrocephalus?
obstruction to flow outside ventricular system (e.g in subarachnoid space or arachnoid granulations)
what happens if hydrocephalus occurs before or after closure of cranial sutures?
before closure = cranial enlargement
after closure = expansion of ventricles and increase in ICP
what is hydrocephalus ex vacuo?
dilation of the ventricular system and a compensatory increase in CSF volume secondary to loss of brain parenchyma (e.g alzheimers)
5 effects of raised ICP?
intracranial shifts and herniations - “coning”
midline shift
distortion and pressure on cranial nerves and vital neurological centres
impaired blood flow
reduced consciousness
physiological causes of raised ICP?
hypoxia
hypercapnia
pain
4 types of shifts/herniation?
subfalcine
tentorial/central
cerebellar
transcervical
describe a subfalcine herniation
unilateral/asymmetrical expansion of cerebral hemisphere which displace singulate gyrus under falx cerebri
can compress anterior cerebellar artery, sensory/motor weakness in leg
describe tentorial/central herniation
medial aspect of temporal lobe herniates over tentorium cerebelli
compression of CN III (blown pupil and impaired ocular movement)
describe cerebellar herniation
displacement of cerebellar tonsils through foramen magnum
compresses resp centres
describe transcervical herniation
swollen brain herniates through any weakness in skull (e.g after fracture)
signs of raised ICP?
papilloedema
headache (worse on lying down, coughing etc)
nausea and vomiting
neck stiffness
general clinical presentation of brain tumours?
focal symptoms headache (worse in morning) vomiting seizures visual disturbance focal deficit papilloedema
most common site of brain tumour in adults/children?
kids = below tentorium cerebelli adults = above