ESSENTIALS OF DIAGNOSIS
Sudden onset of focal neurologic deficits
Initial computed tomography (CT) scan of the head to exclude intracranial hemorrhage or mass lesion
Follow-up brain imaging showing evidence of acute infarction
Rapid diagnosis is required to initiate thrombolytic therapy within 3 hours of onset and thrombectomy within 24 hours
Stroke is one of the four leading causes of death in most countries and the leading cause of severe neurologic disability in adults. In the United States alone, there are more than 750,000 new strokes each year. The risk of stroke increases with each decade of life, with the highest incidence of stroke occurring in people older than 80 years. Men are at slightly higher risk of stroke compared to women except after age 80, and in younger ages peripartum stroke is an important consideration. Stroke has a disproportionate impact on non-Hispanic blacks in the United States and in people in the southeastern states.
The World Health Organization defines stroke as “rapidly developing clinical signs of focal (at times global) disturbance of cerebral function, lasting for more than 24 hours or leading to death, with no apparent cause other than of vascular origin.” Stroke, therefore, encompasses three major cerebrovascular disorders: ischemic stroke, primary intracerebral hemorrhage, and spontaneous subarachnoid hemorrhage. Ischemic stroke, or cerebral infarction, is the most common, accounting for approximately 70–80% of all strokes. Intracerebral hemorrhage and subarachnoid hemorrhage are discussed in another chapter.
Formerly, a transient ischemic attack (TIA) was defined as an episode of focal brain ischemia with symptom resolution within 24 hours. It was recognized, however, that most TIAs resolve within minutes, whereas longer lasting symptoms would have a high proportion of infarction present on magnetic resonance imaging (MRI). The current definition of TIA therefore now includes focal neurologic symptoms of presumed ischemic origin with the absence of infarction on brain imaging. Substantial risk nonetheless remains after TIA, with up to 15% of patients having a stroke within 90 days, the bulk of which occur in the first 48 hours. Due to the shared pathophysiology and risk of subsequent stroke, the approach to TIA and ischemic stroke is similar.
Ischemic stroke is caused by focal cerebral ischemia: a localized reduction in blood flow sufficient to disrupt neuronal metabolism and function. If ischemia is not reversed within a critical period, irreversible cellular injury ensues, resulting in cerebral infarction. Pathologically, cerebral infarction appears as focal pan-necrosis of neurons, glia, and blood vessels. The underlying cause of the reduction in cerebral blood flow guides acute stroke treatment and informs secondary prevention and risk of recurrence. Thus, one of the primary goals in the evaluation of an ischemic stroke is to determine the stroke subtype. One of the most common ischemic stroke classification schemes defines common stroke subtypes as follows: cardioembolic, large artery atherosclerosis, lacunar, and ...