SAH

Question 1

def SAH

Answer 1

arterial haemorrhage into the subarachnoid space, spontaneous

Question 2

aetiology fo SAH

Answer 2

rupture of saccular (berry aneurysm) haemorrhage at the base of the brain - usually at the circle of willis - 85% - at junction of posterior communicating artery with tyhe internal carotid, or anterior communicating with anterior cerebral, or bifercation of the middle cerebral

perimesencephalic haemorrhage - eg parenchymal haemorrhages tracking onto the surface of the brain - 10%

arteriovenous malformations, bleeding diatheses, vertebral or carotid artery dissection with intracranial extension, mycotic aneurysms, drug abuse (eg cocaine, amphetamine) 5%

encephalitis, vasculitis, tumour invading bv, idiopathic

Question 3

associations with SAH

Answer 3

previous aneurysmal SAH - new form, old get bigger

HTN,

smoking,

excess alcohol intake

saccular aneurysms associated with polycystic kidney disease

Marfan’s syndrome

pseudoxanthoma elasticum

ehlers-danlos - associated berry aneurysm

bleeding disorders

SBE - mycotic aneurysm

FH - 3-5x increased risk in close relatives

aortic coarctation - associated with berry aneurysm

Question 4

epi SAH

Answer 4

annual incidence 10 in 100000

50yrs

Question 5

sx of SAH

Answer 5

sudden onset of severe headache - classically described as if been hit on the back of the head, thunderclap

nausea

vomiting

neck stiffness

photophobia

reduced consciousness - coma/drowsiness may last for days

seizure

warning ‘sentinal’ headache - perhaps due to small warning leak from aneurusm (6%)

Question 6

signs of SAH

Answer 6

meningism

• neck stiffness and Kernig’s sign (takes 6hr to develop) - resistance or pain on knee extension when hip flexed
• because of irritation of meninges by blood
• pyrexia may occur

GCS - assess and regularly monitor for deterioration

increased ICP

• papilloedema
• CN 3 or 4 palsy
• htn
• bradycardia

fundoscopy

• rarely subhyaloid haemorrhage - between retina and viteous membrane
• Terson’s syndrome: retinal, subhyaloid and vitreous bleed = 5x increased mortality

focal neurological

• develop on second day and are caused by ischemia from vasospasm and reduced brain function
• aneurysms may cause pressure on cranial nerves = ophthalmoplegia - CN3 or 6 palsy
• at presentation may suggest intracerebral haematoma or site of aneurysm eg pupil change - CN3 palsy with posterior communicating aneurysm

Question 7

Ix for SAH

Answer 7

blood

• FBC
• UE
• ESR/CRP
• clotting ?bleeding diathesis

urgent CT scan

• hyperdense regions in the basal regions of the skull (caused by blood in the subarachnoid space)
• identify intraparenchymal or intraventricular haemorrhages
• detects >95% in 1st 24hrs

angiography (CT or intra-arterial) - detect the source of bleeding if candidate for surgery or endovascular treatment

LP

• if CT -ve but history suggestive, and no CI
• >12hr after onset - allow breakdown RBC
• high opening pressure
• high red cells
• few white cells
• xanthochromia (straw coloured CSF) because of breakdown of Hb - confirmed by spectrophotometry of CSF supernatant after centrifugation.