Functional differentiation of multiple perilesional zones after focal cerebral ischemia

Transient and permanent focal cerebral ischemia results in a series of typi cal pathophysiologic events. These consequences evolve in time and space an d are not limited to the lesion itself, but they can be observed in periles ional (penumbra) and widespread ipsi- and sometimes contralateral remote ar eas (diaschisis). The extent of these areas is variable depending on factor s such as the type of ischemia, the model, and the functional modality inve stigated. This review describes some typical alterations attributable to fo cal cerebral ischemia using the following classification scheme to separate different lesioned and perilesional areas: (1) The lesion core is the brai n area with irreversible ischemic damage. (2) The penumbra is a brain regio n that suffers from ischemia, but in which the ischemic damage is potential ly, or at least partially, reversible. (3) Remote brain areas are brain are as that are not directly affected by ischemia. With respect to the etiology , several broad categories of remote changes may be differentiated: (3a) re mote changes caused by brain edema; (3b) remote changes caused by waves of spreading depression: (3c) remote changes in projection areas; and (3d) rem ote changes because of reactive plasticity and systemic effects. The variou s perilesional areas are not necessarily homogeneous; but a broad different iation of separate topographic perilesional areas according to their functi onal state and sequelae allows segregation into several signaling cascades, and may help to understand the functional consequences and adaptive proces ses after focal brain ischemia.