Figure 3.

Location and extent of microglia activation after focal subcortical ischemia as determined by [¹¹C](R)-PK11195 and HRRT-PET in conjunction with diffusion tensor imaging (DTI) MRI. Various microglia activation patterns can be observed after focal cerebral ischemia in humans depending on the affection of the pyramidal tract and the primary lesion size. Acutely activated microglia at the infarct site that decreases after 6 months (A) are related with good clinical outcome although microglia activation in the brain stem as sign of anterograde axonal degeneration persists. Lesions that cause a complete transection of the pyramidal tract as determined by DTI are related to persistent microglia activity at the site of infarction and in the brain stem at 6 months and are related to a poor outcome (B). In patients where the pyramidal tract is not affected, microglia activation occurs only at the infarct site and not in the brain stem (C). (Figure reprinted with permission from Thiel et al, 2010.) FA, fractional anisotropy; HRRT, high resolution research tomograph; MRI, magnetic resonance imaging; PET, positron-emission tomography.