An increase in the number of astrocytes, frequently observed in an irregular, poorly or moderately well defined zone adjacent to degenerative lesions (e.g., encephalomalacia), focal inflammations (e.g., abscesses), or certain neoplasms in the brain; in some instances, astrocytosis may be diffuse in a relatively large region; astrocytosis represents a reparative defense mechanism.

astrocytosis cerebri