10.3 Meninges & SAH Flashcards
name some common sites of SAH, and why the result can be significant
anterior communicating artery/proximal ACA
-compress optic chaism, ay affect frontal lobe
posterior communicating artery
-compress CN3 = ipsilateral third nerve palsy
middle cerebral artery bifurcation to superior and inferior divisions
bleeding into the subarachnoid space causes early brain injury. what are some mechanisms of this?
microthormbi- occlude distal branches
vasoconstriction- CSF irritates cerebral arteries, so less blood to brain
cerebral oedema- mass effect of bleed, inflammatory response
apoptosis of brain cells
bleeding into the subarachnoid space causes cellular changes. what are some mechanisms of this?
sympathetic activation= Cushing response
myocardial necrosis
systemic inflammatory response
main investigation for SAH, and what you’d see
secondary imaging if bleed confirmed?
CT
star shaped, blood in ventricles
CT angiogram
if CT inconclusive, a LP can be done. Whats important about the timing?
at least 6 hourd from onset of symptoms (preferably 12) to allow RBC lysis to release bilirubin and create xanthochromia, which rules out a traumatic tap from damaging blood vessels
in SAH, fluids and what else could be given to support the circulation?
nimodipine- CCB, alleviate cerebral vasospasm and secondary ischaemia
typical organisms causing meningitis in neonates
-e coli
-group b strep
-listeria monocytogenes
typical organisms causing meningitis in children
-haemophilus influenzae B
-neisseria meningitidis
typical organisms causing meningitis in elderly
-strep pneumoniae
-listeria monocytogenes
risk factors for meningitis
-CSF elects e.g. spina bifida
-extremed of age
-cochlear implants - route for bacteria colonisation to brain
-diabetes
-splenectomy
-crowding
clinical examination signs associate with meningitis
kernig
brudzinski
symptoms of meningitis in babies
inconsolable crying
off feeds
rigid/floppy
bulging fontanelle
pathophysiology of meningitis
normal bar terra enter circulation = bactereamia
damages vessel walls I. brain and meninges, enter sub arachnoid space
multiply - purulent CSF, meningeal inflammation
vasospasm of cerebral vessels = infarction
oedema= raised ICP
which type of meningitis commonly causes a macropapular rash?
meningococcal septicaemia
investigations for meningitis
bloods
sepsis screen
PCR
CXR/mid stream urine for specific focus
LP
