A transient ischemic attack (TIA) is a transient episode of neurologic dysfunction caused by ischemia (loss of blood flow) – either focal brain, spinal cord, or retinal – without acute infarction (tissue death). TIAs have the same underlying cause as strokes: a disruption of cerebral blood flow (CBF), and are often referred to as mini-strokes. Symptoms caused by a TIA resolve in 24 hours or less. TIA was originally defined clinically by the temporary nature of less than 24 hours of the associated neurologic symptoms. Recently, the American Heart Association and American Stroke Association (AHA/ASA) defined TIA as transient episode of neurologic dysfunction caused by focal brain, spinal cord, or retinal ischemia, without acute infarction. TIAs cause the same symptoms associated with stroke, such as contralateral paralysis (opposite side of body from affected brain hemisphere) or sudden weakness or numbness. A TIA may cause sudden dimming or loss of vision (amaurosis fugax), aphasia, slurred speech (dysarthria) and mental confusion. But unlike a stroke, the symptoms of a TIA can resolve within a few minutes or within 24 hours. Brain injury may still occur in a TIA lasting only a few minutes. Having a TIA is a risk factor for eventually having a stroke or a silent stroke.
A silent stroke, also known as silent cerebral infarct (SCI), differs from a TIA in that there are no immediately observable symptoms. An SCI may still cause long lasting neurological dysfunction affecting such areas as mood, personality and cognition. An SCI often occurs before or after a TIA or major stroke.
A cerebral infarct that lasts longer than 24 hours but fewer than 72 hours is called a reversible ischemic neurologic deficit or RIND