THE CAPSULAR WARNING SYNDROME - PATHOGENESIS AND CLINICAL-FEATURES

Transient ischemic attacks (TIAs) are not homogeneous and may consist of subsets with mechanisms as varied as their stroke counterparts. We describe a form of TIA in 50 patients where crescendo episodes of isch emia were restricted to the region of the internal capsule, usually ca using symptoms affecting face, arm, and leg. These patients composed 4 .5% of a consecutive series of patients admitted with TIAs over a 15-y ear period and 33% of all TIAs classified as subcortical. We believe t hat the ischemia was most often due to hemodynamic phenomena in diseas ed, single, small penetrating vessels. When cerebral infarction develo ped, it was usually lacunar and involved a single penetrating vessel, although occasionally striatocapsular or anterior choroidal artery ter ritory infarction occurred. There was no evidence of artery-to-artery or heart-to-artery embolism. Resistance to various forms of therapy, i ncluding hemodiluting, anticoagulant, and thrombolytic agents, was com mon. Because of dramatic and easily recognizable clinical presentation , apparent specific pathophysiologic mechanism, and the development of early capsular stroke in a high proportion of cases (42%), we have te rmed this the ''capsular warning syndrome.''