The aneurysms are balloon like swellings of the blood vessels of the brain. Their incidence is 1 in 1000 in general population. The cause of the aneurysms is not well known. They are common in females. They are described to be present in certain genetic conditions like autosomal dominant polycystic kidney disease, Ehler Danlos syndrome etc. Hypertension is known to accelerate the growth of the aneurysms.