inflammation of brain tissue caused by infection with the varicella-zoster virus (herpesvirus 3, human). This condition is associated with immunocompromised states, including the acquired immunodeficiency syndrome. Pathologically, the virus tends to induce a vasculopathy and infect oligodendrocytes and ependymal cells, leading to cerebral infarction, multifocal regions of demyelination, and periventricular necrosis. Manifestations of varicella encephalitis usually occur 5-7 days after onset of herpes zoster and include headache; vomiting; lethargy; focal neurologic deficits; fever; and coma. (From Joynt, Clinical neurology, 1996, Ch 26, pp29-32; Hum Pathol 1996 Sep;27(9):927-38)