Aneurysms are acquired lesions related to hemodynamic stress on the arterial walls at bifurcation points and bends. Saccular or berry aneurysms are specific to the intracranial arteries because their walls lack an external elastic lamina and contain a very thin adventitia—factors that may predispose to the formation of aneurysms.
An additional feature is that they lie unsupported in the subarachnoid space.Finland and South or Central America as the reference group. Overall incidences were 9.1 (95% CI 8.8 to 9.5) per 100 000 person?years in the reference group (42 studies); 22.7 (95% CI 21.9 to 23.5) in Japan (seven studies); 19.7 (95% CI 18.1 to 21.3) in Finland (six studies); and 4.2 (95% CI 3.1 to 5.7) in South and Central America (three studies) (fig 22).). The incidence in Japan was 2.5 (95% CI 2.4 to 2.6) times higher than that of the reference region and in Finland 2.2 (95% CI 2.0 to 2.4) times higher, whereas the incidence in South and Central America was 2.2 (95% CI 1.6 to 2.9) times lower.
Treatement is • Remove large collections of blood or relieve pressure on the brain if the hemorrhage is due to an injury • Repair the aneurysm if the hemorrhage is due to an aneurysm rupture If the person is critically ill, surgery may have to wait until the person is more stable. Ongoing Research is being done atSubarachnoid haemorrhage centres.