10. Subarachnoid haemorrhage and Meningitis Flashcards
what percentage of strokes are due to subarachnoid haemorrhage?
6%
what is the epidemiology of subarachnoid haemorrhages?
female
under 50
what is the prognosis of a subarachnoid haemorrhage?
50% mortality
60% suffer from long term morbidity
what are the risk factors of a subarachnoid haemorrhage?
hypertension, smoking, alcohol consumption, predisposition to aneurysm formation, family history, associated conditions such as CKD, marfans and neurofibromatosis, trauma, cocaine use
what is the most common cause of a subarachnoid haemorrhage?
rupture of an aneurysm in the circle of willis
what is an aneurysm?
a weakness in a vessel (usually artery) wall which can cause an abnormal bulge
- usually a berry aneurysm
what are some common causes of aneurysm?
genetic predisposition, haemodynamic effects at branch points(higher flowing rate as branches get smaller causing turbulence)
what are the most common sites of berry aneuyrsms and what are the clinical effects?
Anterior communicating artery/proximal anterior cerebral artery (30%) = compress optic chiasm, frontal lobe, and pituitary
Posterior communicating artery (25%) = compress adjacent oculomotor nerve causing ipsilateral third nerve palsy
Bifurcation of the middle cerebral artery as it splits into superior and inferior divisions (20%)
what are the pathological changes that occur as a result of bleeding into the subarachnoid space?
microthrombi which occlude more distal branches due to platelet aggregation
vasoconstriction as a result of blood in the CSF irritating cerebral arteries
cerebral oedema due to an inflammatory response to tissue hypoxia and blood
apoptosis of brain cells
oxidative stress due to reperfusion injury
release of inflammatory mediators
what are the systemic complications of a subarachnoid haemorrhage?
sympathetic activation - early cushing response
myocardial necrosis - sympathetic activitation,
systemic inflammatory response
what are the clinical features of a subarachnoid haemorrhage?
thunderclap headache
frequent loss of consciousness and confusion
meningism - neck stiffness, photophobia, headache
may have focal neurology
may be history of mild headache (sentinel bleed)
may present as cardiac arrest id ICP rises rapidly leading to profound cushing response
what investigations are used for a suspected subarachnoid haemorrhage?
CT head which shows prominent filling of the basal cisterns in a five pointed star pattern
blood may be seen in ventricles
lumbar puncture
what investigations are used if bleeding is confirmed?
CT angiogram - direct visualising of bleeding aneurysm or sac
what results from a lumbar puncture would indicate a subarachnoid haemorrhage?
increased opening pressure frank blood or xanthochromia (yellow colouring of CSF due to metabolism of Hb to billirubin within subarachnoid haemorrhage high protein white cells often not raised glucose not affected high red cell count
how are subarachnoid haemorrhages treated?
support airway
give oxygen
fluids
nimodipine may alleviate cerebral vasospasm
looking at neurological observations which indicates an increased raised ICP
decompressive surgery (craniectomy)
coiling (insertion of platinum wire into aneurysm sac)
clipping (placement of spring clip around neck of aneurysm causing it to lose blood supply)
what are the typical organisms involved in neonates?
E.coli, group B streptococcus, listeria monocytogenes
what are the typical organisms involved in children?
H.influenzae, N.Meningitidis
what are the typical organisms involved in elderly?
S.penumoniae, Listeria monocytogenes
what are the risk factors for meningitis?
CSF defects (spina bifida), spinal procedures (surgery, lumbar puncture), endocarditis, diabetes, alcoholism, splenectomy, crowded housing
what are the clinical features of meningitis?
headache, stiffness, photophobia (common)
flu like, joint pains, stiffness, seizure, meningococcal rash, drowsiness, shock, babies - inconsolable crying, off feeds, rigidity/floppiness, bulging fontanelle
what are the pathophysiology of meningitis?
bacteria living in the nose gain entry to the circulation and cause a bacteraemia, which then cause damage to vessel walls in the brain and meninges allowing the pathogen to enter the subarachnoid space, they then multiply rapidly causing purulent CSF and severe meningea inflammation. vasoplasm of cerebral vessels can cause cerebral infarction. the oedema of brain parenchyma can cause raised ICP
what dermatological feature is indictive of meningitis?
maculopapular rash seen in meningococcal septicaemia due to microvascular thrombosus due to sluggish circulation, impaired fibrinolysis, increased tissue factor expression in endothelial cells
what investigations are used to test for meningitis?
bloods - sepsis screen, PCR
chest x ray or midstream urine
lumbar puncture
what lumbar puncture findings indicate the differential organisms of meningitis>
bacterial - cloudy CSF, high protein, high white cells, low glucose
viral - clear or cloduy, protein level normal or rasied, high white cells, normal glucose
what is the treatment of meningitis?
supportive - analgesia, antipyretics, fluids
medical - IV ceftraxione, dexamethasone to prevent hearing loss
if viral - aciclovir for herpes or gancliclovir for CMV
what are the complications of meningitis?
septic shock DIC Coma cerebral oedema raised ICP DEATH SIADH seizures hearing loss intellectual deficits hydrocephalus focal paralysis
