Cerebrovascular disease is any disease affecting an artery within the brain, or supplying blood to the brain. The most common is atherosclerosis, where plaques (fatty deposits) form, leading to narrowing of the arteries. There may also be a defect or weakness in a blood vessel in the brain which can cause an aneurysm (ballooning of an artery).

Cerebrovascular disease makes it more likely that a cerebrovascular accident will occur, when there is a sudden blockage or rupture of a blood vessel within the brain. Blockage may be due to a blood clot forming in the cerebral arteries (a thrombosis) or by a fragment of material (blood clot, piece of tissue, cholesterol or various other substances) travelling in the blood stream (an embolism).

A thrombosis or an embolism, which completely blocks the blood supply to a part of the brain or a ruptured blood vessel causing bleeding within the brain, causes a stroke.

Transient ischaemic attacks (TIAs) are usually caused by an embolism, which blocks small arteries within the brain leading to a loss of brain function in one area. This lasts until the blockage moves on or is broken down, allowing blood to flow again.

Another effect of cerebrovascular disease is dementia. About 10% of cases of dementia are due to small, repeated blockages of arterial branches by atherosclerosis, with progressive overall destruction of brain tissue because it is being deprived of enough blood.