Stroke Differential Diagnosis - Mimics and Chameleons

What historical or physical examination findings suggest an ischemic stroke? What processes may simulate stroke? What are some unusual stroke presentations? Introduction The diagnosis of acute ischemic stroke is often straightforward. The sudden onset of a focal neurologic deficit in a recognizable vascular distribution with a common presentation-such as hemiparesis, facial weakness and aphasia-identifies a common syndrome of acute stroke. But differential diagnostic problems remain because there are several subtypes of stroke and also because some non-vascular disorders may have clinical pictures that appear identical to strokes. This talk will briefly review the differential diagnosis of stroke starting with stroke sub-types. Stroke " mimics, " non-vascular conditions that simulate stroke, will then be covered in detail. The final discussion addresses unusual clinical pictures that may result from stroke which here are termed stroke " chameleons "-strokes that take on the appearance of something else. Stroke Subtypes The abrupt presentation of acute ischemic stroke results from the abrupt interruption of blood flow to a part of the brain. Most commonly this is from embolic or thrombotic arterial vascular occlusion that may be visualized angiographically in many cases when symptoms are severe enough to warrant acute angiography. 1 Other vascular events which may result in stroke syndromes include lacunar strokes, arteritis, arterial dissections, and cortical venous occlusions. Intraparenchymal intracranial hemorrhage from a variety of causes-the spontaneous or hypertensive hemorrhages, vascular malformations, or aneurysmal origin-are frequently encountered clinically and figure prominently in the initial stroke differential diagnosis. These different processes may be considered stroke subtypes for classification purposes and are listed in the first section of Table 1. The terminology " misclassified " stroke has recently been used to describe patients initially thought to have stroke but later found to have hemorrhage, lacunar infarction, or posterior circulation ischemia after extensive imaging that included magnetic resonance imaging (MRI), magnetic resonance angiography (MRA), diffusion-weighted imaging (DWI), and perfusion-weighted imaging (PWI). One study found that 21% of patients thought to have had anterior circulation ischemic stroke at initial evaluation had other stroke types that had been misclassified. 2 As more advanced imaging techniques move into clinical practice, diagnostic accuracy of assignment to stroke sub-types will continue to improve.