This happens when on of the normal arteries in the brain develops an area of weakness and then balloons. This is usually inherited and not due high blood pressure. Aneurysms can rupture and cause bleeding in and around the brain (Sub Arachnoid haemorrhage). This is a devastating disease that can strike at any age. Unfortunately the mortality of this disease remains high even in our modern era. Aneurysms can either be operated on by placing a clip over the aneurysm or by endovascular techniques which entail "plugging" the aneurysm.