The Ischemic Penumbra: Overview, Definition, and Criteria

Abstract

Prior to the 1970s, ischemic tissue death was generally believed to be relatively sudden and irreversible. When compared to other areas of basic research, the number of investigators involved in experimental cerebral ischemia was relatively few, so progress was slow. Although clinicians were aware of the clinical paradigm in which transient cerebral ischemic attacks occurred with a full recovery within 24 hours without any evidence of cerebral infarction, explanations such as “hypertensive crisis” or “arterial spasm” were proposed to account for these episodes. In the mid-1950s, however, the embolic theory for transient ischemic attacks (TIAs) became widely accepted, which stimulated a numbe..