• Cerebral aneurysm. A cerebral aneurysm is the dilation, bulging or ballooning out of part of a blood vessel in the brain. The cause is unknown, but smoking is known to increase a person’s risk of developing this condition. Aneurysms that break (rupture) or bleed (hemorrhage) into the brain can cause stroke or even death.

  • Blood clots or embolisms. Blood clots are clumps of blood cells and fibrin strands that may form in an injured blood vessel. They can partially or totally block the flow of blood through that vessel. An embolism is a clot or piece of a clot that formed somewhere in the body and then traveled through the bloodstream to another area of the body. Blockage by either a clot or an embolism in the cerebral arteries or carotid arteries will result in a lack of blood flow (and therefore oxygen) to the brain. Called cerebral ischemia, this lack of oxygen could cause a transient attack ischemic or a stroke.

  • Cerebral arteriosclerosis. This condition, in which there is a hardening and narrowing of the arteries in the brain, can increase the risk of a stroke. One type of cerebral arteriosclerosis is cerebra atherosclerosis, which is caused by the buildup of plaque in the vessel.

  • Malformations of blood vessels (e.g., arteriovenous fistulas, an abnormal connection of an artery to a vein or arteriovenous malformations, an abnormal collection of blood vessesls).