C N S  S A H 5th Class
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C N S S A H 5th Class



CNS SAH 5th med students lecture.

CNS SAH 5th med students lecture.



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C N S  S A H 5th Class C N S S A H 5th Class Presentation Transcript

  • Epidemiology :
    • 3/4 are < 65 years.
    • Women are more frequently affected than men.
    • It typically presents with a sudden, severe 'thunderclap' headache (often occipital) which lasts for hours or even days, often accompanied by vomiting.
    • Physical exertion, straining, sexual excitement are common antecedents.
    • There may be loss of consciousness at the onset, so it should be considered if a patient is found comatose.
    • Since it is rare (incidence 6/100 000) & only 1/8 with a sudden severe headache has had a SAH, clinical vigilance is necessary to avoid a missed diagnosis.
    • All patients with a sudden severe headache require investigation to exclude a SAH.
  • EXAM :
    • The patient is usually distressed & irritable, with photophobia.
    • There may be neck stiffness due to subarachnoid blood but this may take some hours to develop.
    • Focal hemisphere signs (hemiparesis, aphasia etc.) may be present at onset if there is an associated intracerebral haematoma.
    • A 3rd nerve palsy may be present due to local pressure from an aneurysm of the posterior communicating artery, though this is rare.
    • Fundoscopy may reveal a subhyaloid haemorrhage, which represents blood tracking along the subarachnoid space around the optic nerve.
  • Pathology :
    • 85% are caused by saccular ('berry') aneurysms bulging out from the bifurcations of the cerebral arteries, particularly in the region of the circle of Willis.
    • These rarely present before the age of 20 years.
    • There is an increased risk in first-degree relatives of those with saccular aneurysms& with polycystic kidney disease & congenital collagen defects, e.g. Ehlers-Danlos syndrome.
    • Of the remainder, 10% are non-aneurysmal haemorrhages (so called peri-mesencephalic haemorrhages), which have a very characteristic appearance on CT& a benign outcome in terms of mortality&recurrence.
    • Some 5% of SAHs are due to rarities including arteriovenous malformations & vertebral artery dissection.
  • Management & prognosis:
    • The immediate mortality of aneurysmal SAH is about 30%.
    • Survivors have a recurrence, or re-bleed, of 40% in the first 4 weeks & 3% annually thereafter.
    • Insertion of platinum coils into an aneurysm (via an endovascular procedure) or surgical clipping of the aneurysm neck reduces the risk of both early & late recurrence.
    • Coiling may be associated with fewer perioperative complications &better outcomes.
    • A re-bleed is not the only cause of early deterioration.
    • The clinician should also consider obstructive hydrocephalus, delayed cerebral ischaemia due to vasospasm, hyponatraemia & systemic complications associated with immobility, e.g. chest infection or pulmonary embolism.
    • Nimodipine (60 mg) is given to prevent vasospasm in the acute phase.