transient ischemic attack (TIA), an episode of cerebrovascular insufficiency, usually associated with partial occlusion of a cerebral artery by an atherosclerotic plaque or an embolus. The symptoms vary with the site and degree of occlusion. Disturbance of normal vision in one or both eyes, dizziness, weakness, dysphasia, numbness, or unconsciousness may occur. The attack usually lasts a few minutes. In rare cases symptoms continue for several hours.
