The definition of TIA is changing. Previously, TIA was defined as a focal cerebral ischemic event with symptoms lasting < 24 hours. As computed tomography and magnetic resonance imaging have become more widely used, up to one-third of patients with TIA have radiological evidence of acute infarction. Therefore, the definition of TIA is moving from time-based to tissue-based, as “a transient episode of neurological dysfunction caused by central nervous system ischemia without acute infarction.” Unilateral weakness and speech disturbances are the most common manifestations of TIA. Unilateral weakness (face, arm, or leg) and speech disturbance (aphasia or dysarthria) are seen in approximately 31%-54% and 25%-42% of TIAs, respectively.
Short-term risk of stroke increases after TIA. The risk of stroke in the days and months after TIA can be estimated using the ABCD2 score.