Stroke mimics and chameleons

The diagnosis of acute ischemic stroke is often straightforward. The sudden onset of a focal neurologic deficit in a recognizable intracranial vascular distribution with a common clinical syndrome such as hemiparesis, facial weakness, and aphasia identifies a clinical syndrome of acute stroke. Differential diagnostic problems remain, however, because there are several subtypes of stroke, and some nonvascular clinical problems may result in pictures identical to common stroke syndromes. This article briefly reviews the differential diagnosis of stroke starting with the stroke subtypes, which are extensively covered in a following article. Stroke "mimics," nonvascular conditions that may simulate stroke, are discussed in greater detail. An old clinical axiom expresses the idea that "uncommon manifestations of common clinical problems are more common than common manifestations of uncommon clinical problems." Uncommon manifestations of stroke may seem to be another disease process. This article also addresses a few of these unusual clinical syndromes that may result from ischemic stroke that are termed "stroke chameleons"-strokes resembling another clinical entity. Expanding the differential diagnosis of acute neurologic deficits is the goal of reviewing these stroke mimics and unusual clinical pictures of acute stroke. This discussion aids the clinician in keeping a broad differential diagnosis during patient evaluation and in avoiding premature diagnostic closure. With emerging therapies for acute stroke, the rapid and reliable diagnosis of ischemic stroke is an area of continuing concern.