Sub-arachnoid haemorrhage (SAH): Treatment, symptoms, advice and help
A sub-arachnoid haemorrhage (SAH)is the phenomenon of bleeding into the subarachnoid space—the area between the arachnoid membrane and the pia mater surrounding the brain. This may occur spontaneously or may result from a head injury.
SAH: Incidence, age and sex
Sub-arachnoid haemorrhage (SAH) is less than common than other types of stroke and affects about 6 / 100, 000 of the population. Women are affected more commonly than men and the condition usually presents before the age of 65. The immediate is about 30% and survivors have a recurrence, or re-bleed, rate of about 40% in the first 4 weeks and 3% annually thereafter.
Signs & symptoms of SAH
Sub-arachnoid haemorrhage typically presents with a sudden, severe headache (often occipital) which lasts for hours or even days, often accompanied by vomiting. There may be loss of consciousness at the onset. On examination, the patient is usually distressed and irritable, with photophobia. There may be neck stiffness due to subarachnoid blood but this may take some hours to develop. Focal signs such as hemiparesis or asphasia may be present at onset if there is an associated intra-cerebral haematoma.
Investigations: Lumbar puncture is the investigation of first choice and should be performed after 12 hours from the symptom onset, if possible. The diagnosis of SAH can be made by a CT scan, but a negative result does not exclude the diagnosis since small amounts of blood in the sub-arachnoid space, cannot be detected by a CT. If either of these tests is positive, cerebral angiography is required to determine the optimal approach to prevent recurrent bleeding.
Causes and prevention of SAH
Eighty-five percent of spontaneous SAH are caused by saccular or ‘berry’ aneurysms arising from the bifurcation of cerebral arteries, particularly in the region of the circle of Willis. There is an increased risk in first degree relatives of those with saccular aneurysms, and an increased risk of SAH in patients with polycystic kidney disease and congenital connective tissue defects such as Ehlers-Danlos syndrome. In about 10% of cases, SAH are non-aneurysmal haemorrhages.
Complications include obstructive hydrocephalus (possibly requiring draining via a shunt), delayed cerebral ischaemia due to vasospasm (requiring vasodilators), hyponatremia (requiring water restriction) and systemic complications associated with immobility such as chest infection and venous thrombosis.
Insertion of platinum coils into an aneurysm (via an endovascular procedure) or surgical clipping of the aneurysm neck reduces the risk of both early and late recurrence.
Arteriovenous malformations can be managed in several different ways including surgical removal, ligation of the blood vessels that feed or drain the lesion, or injection of material to occlude the fistula or draining veins. Nimodipine (30 – 60mg intravenously. for 5-14 days, followed by 360 mg orally for a further 7 days) is usually given to prevent vasopasm in the acute phase.