An abnormal blood-filled bulge of a blood vessel and especially an artery resulting from weakening (as from disease) of the vessel wall. Most often a ruptured brain aneurysm occurs in the space between the brain and the thin tissues covering the brain.

Brain Aneurysm/AVM Center

The Brain Aneurysm/AVM Center section of the Massachusetts General Hospital/Harvard Medical School neurosurgical site includes extensive information about assessment and treatment of neurovascular problems of the brain and spinal cord, including stroke, aneurysm, and arteriovenous malformation. The site includes links to stroke sites helpful to patients, families and care givers, and health professionals.

NINDS: Cerebral Aneurysm Fact Sheet

Provided by the National Institute of Neurological Disorders and Stroke, the page provides scientific, but accessible, information on types of aneurysms, warning signs, risk factors, and symptoms, as well as diagnosis methods, research, treatment, and recovery.

Toronto Brain Vascular Malformation Study Group

This University of Toronto site offers explanations and definitions of multiple types of brain vascular malformations, with treatment information and a medical dictionary. Note that some information on the site is specific to Toronto patients.