10. Subarachnoid haemorrhage and Meningitis

Question 1

what percentage of strokes are due to subarachnoid haemorrhage?

Answer 1

6%

Question 2

what is the epidemiology of subarachnoid haemorrhages?

Answer 2

female

under 50

Question 3

what is the prognosis of a subarachnoid haemorrhage?

Answer 3

50% mortality

60% suffer from long term morbidity

Question 4

what are the risk factors of a subarachnoid haemorrhage?

Answer 4

hypertension, smoking, alcohol consumption, predisposition to aneurysm formation, family history, associated conditions such as CKD, marfans and neurofibromatosis, trauma, cocaine use

Question 5

what is the most common cause of a subarachnoid haemorrhage?

Answer 5

rupture of an aneurysm in the circle of willis

Question 6

what is an aneurysm?

Answer 6

a weakness in a vessel (usually artery) wall which can cause an abnormal bulge
- usually a berry aneurysm

Question 7

what are some common causes of aneurysm?

Answer 7

genetic predisposition, haemodynamic effects at branch points(higher flowing rate as branches get smaller causing turbulence)

Question 8

what are the most common sites of berry aneuyrsms and what are the clinical effects?

Answer 8

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%)

Question 9

what are the pathological changes that occur as a result of bleeding into the subarachnoid space?

Answer 9

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

Question 10

what are the systemic complications of a subarachnoid haemorrhage?

Answer 10

sympathetic activation - early cushing response
myocardial necrosis - sympathetic activitation,
systemic inflammatory response

Question 11

what are the clinical features of a subarachnoid haemorrhage?

Answer 11

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

Question 12

what investigations are used for a suspected subarachnoid haemorrhage?

Answer 12

CT head which shows prominent filling of the basal cisterns in a five pointed star pattern
blood may be seen in ventricles
lumbar puncture

Question 13

what investigations are used if bleeding is confirmed?

Answer 13

CT angiogram - direct visualising of bleeding aneurysm or sac

Question 14

what results from a lumbar puncture would indicate a subarachnoid haemorrhage?

Answer 14

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

Question 15

how are subarachnoid haemorrhages treated?

Answer 15

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)

Question 16

what are the typical organisms involved in neonates?

Answer 16

E.coli, group B streptococcus, listeria monocytogenes

Question 17

what are the typical organisms involved in children?

Answer 17

H.influenzae, N.Meningitidis

Question 18

what are the typical organisms involved in elderly?

Answer 18

S.penumoniae, Listeria monocytogenes

Question 19

what are the risk factors for meningitis?

Answer 19

CSF defects (spina bifida), spinal procedures (surgery, lumbar puncture), endocarditis, diabetes, alcoholism, splenectomy, crowded housing

Question 20

what are the clinical features of meningitis?

Answer 20

headache, stiffness, photophobia (common)
flu like, joint pains, stiffness, seizure, meningococcal rash, drowsiness, shock, babies - inconsolable crying, off feeds, rigidity/floppiness, bulging fontanelle

Question 21

what are the pathophysiology of meningitis?

Answer 21

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

Question 22

what dermatological feature is indictive of meningitis?

Answer 22

maculopapular rash seen in meningococcal septicaemia due to microvascular thrombosus due to sluggish circulation, impaired fibrinolysis, increased tissue factor expression in endothelial cells

Question 23

what investigations are used to test for meningitis?

Answer 23

bloods - sepsis screen, PCR
chest x ray or midstream urine
lumbar puncture

Question 24

what lumbar puncture findings indicate the differential organisms of meningitis>

Answer 24

bacterial - cloudy CSF, high protein, high white cells, low glucose
viral - clear or cloduy, protein level normal or rasied, high white cells, normal glucose

Question 25

what is the treatment of meningitis?

Answer 25

supportive - analgesia, antipyretics, fluids
medical - IV ceftraxione, dexamethasone to prevent hearing loss
if viral - aciclovir for herpes or gancliclovir for CMV

Question 26

what are the complications of meningitis?

Answer 26

septic shock
DIC
Coma
cerebral oedema
raised ICP
DEATH
SIADH
seizures
hearing loss
intellectual deficits
hydrocephalus
focal paralysis