Encephalitis By John E Greenlee, MD, University of Utah Health Reviewed / Revised Mar 2022 | Modified Sep 2022 View Patient Education Etiology Pathophysiology Symptoms and Signs Diagnosis Prognosis Treatment Key Points Topic Resources Some Arboviral Encephalitides Encephalitis is inflammation of the parenchyma of the brain, resulting from direct viral invasion or occurring as a postinfectious immunologic complication caused by a hypersensitivity reaction to a virus or another foreign protein.