Early cerebritis (first ~5 days): Represents early focal infection with localized polymorphonuclear leukocytes (PMNs), edema, scattered necrosis, and petechial hemorrhage. Toxic changes in neurons with perivascular infiltrates are present. The lesion is poorly demarcated from surrounding brain.
Late cerebritis (5–14 days): Reticular matrix formation begins leading to a rim of thin granulation tissue at the periphery. Necrotic foci also coalesce leading to the development of a necrotic center.