Stroke (cerebrovascular accident)

Sudden disturbance of blood supply to the brain, possibly leading to loss of faculties (including loss of feeling and paralysis). In roughly three-quarters of cases the cause is narrowing of a blood vessel and possible clot formation, leading to paralysis or aphasia, the inability to speak. These symptoms can be shortlived, if the blood clot dissolves quickly (when it is known as TIA, transient ischemic attack, a temporary disturbance of the blood supply). More serious is a cerebral infarction, after which the symptoms are more likely to persist.