Study of Circle of Willis in 1021 consecutive autopsies: incidence of aneurysms, anatomical variations and atherosclerosis.

Incidence of subarachnoid haemorrhage from aneurysmal rupture is very low in India when compared with that in the Western world and Japan. Either they are not recognised or diagnosed adequately or there may be a true decreased geographical/racial incidence. To have an idea of the true incidence of aneurysms, a study of Circle of Willis with its anatomical variations and incidence of atherosclerosis was carried out in 1021 consecutive autopsies. The incidence of anatomical variations was slightly less than that seen in most of the other studies. Atherosclerosis was seen in 9.2% of the Circles of Willis. There were only two aneurysms, both located at the bifurcation of middle cerebral artery. This incidence of 0.2% is definitely much lower than that seen in other series, thus, suggesting that the incidence of subarachnoid haemorrhage from aneurysmal rupture is likely to be genuinely less in India.