Evolving stroke and the ischemic penumbra

Deterioration of the neurologic deficits that occur hours or even days after the initial presentation is a well-recognized feature of ischemic stroke. In several recent series of prospectively evaluated ischemic stroke patients, the frequency of neurologic worsening ranged from 26 to 43%, and the rate of deterioration was similar in patients evaluated either within 6 to 8 hours or within 1 to 2 days after the onset of symptoms. 1-3 These rates of progression were similar to those previously observed by Jones and Millikan 4 and Jones et al. 5 in patients with either carotid or vertebrobasilar arterial occlusions who were evaluated within 36 hours of stroke onset, although a higher percentage of vertebrobasilar system stroke patients deteriorated at a later time. The definition of neurologic worsening after stroke has varied from study to study, making direct comparisons difficult. With the advent of valid, reproducible neurologic scoring scales, such as the NIH Stroke Scale and the Scandinavian Stroke Scale, a more precise perspective on short-term clinical worsening after acute ischemic stroke will be available from the data that the current plethora of acute stroke intervention trials will provide. 6 The factors that make the deficit worsen are not known. The object of this review is to advance the concept that, in some patients with ischemic stroke, the progression of the neurologic deficits shortly after the ictus relates to the deterioration of the local circulation in which an initially ischemic, but functional, region progresses to a non-functional state and ultimately to infarction. The concept of evolving or progressing stroke initially appeared in the 1950s. 7,8 Several mechanisms potentially contribute to the phenomenon of evolving stroke, and early authors emphasized thrombus propagation despite scarce confirmation of this hypothesis. 9 Other potential mechanisms for the increasing clinical deterioration that may occur during the …