Aneurysm - An abnormal widening or ballooning of a section of a blood vessel.  Aneurysms can rupture, leading to stroke.

Basilar Artery - The artery that supplies blood to the cerebellum, the brainstem, and the back of the brain.

Brainstem - The brain structure that is the major communication route among the brain, spinal cord, and peripheral nerves; controls heart rate, breathing, and other vital functions.

Cerebral Infarction - The death of part of the brain from a lack of oxygen-carrying blood.

Dysarthria - a language disorder characterized by difficulty with speaking or forming words.

Dysphagia - trouble eating and swallowing.

Embolism - A blockage of blood flow through a vessel in the brain by a blood clot that formed elsewhere in the body and traveled to the brain.

Hemiparesis - weakness on one side of the body. 

Hemiplegia - Paralysis of one side of the body.

Hemorrhage - Bleeding in the brain (intracerebral hemmorage) caused by the rupture of an intracranial (within the head) blood vessel.

Infarct - An area of tissue death due to a local lack of oxygen.

Ischemic - An ischemic stroke is death of an area of brain tissue (cerebral infarction) resulting from an inadequate supply of blood and oxygen to the brain due to blockage of an artery.

Paresis (paretic) - Incomplete paralysis or weakness of the limbs. 

Plegia - Lack of voluntary movement. 

Pons - A specific section of the brain formed by the rounded prominence on the front surface of the brainstem.

Subarachnoid hemorrhage - A cause of some strokes in which arteries on the surface of the brain begin bleeding.

Thrombosis - A blockage of blood flow through a vessel in the brain by a blood clot that formed in the brain itself.

Vertebral Artery - One of two blood vessels that run up the back of the neck and join at the base of the skull to form the basilar artery.