The Spectrum of Acute Encephalitis
Clinical question: What characteristics in patients with acute encephalitis portend a worse prognosis?
Background: Acute encephalitis is a serious neurologic disease with high levels of associated morbidity, mortality, and cost of care. Yet, little is known about the factors that affect the outcome of patients with encephalitis.
Study design: Retrospective chart review of all consecutive patients diagnosed with acute encephalitis.
Setting: Mayo Clinic, Rochester, Minn.
Synopsis: A retrospective chart review revealed 198 patients with encephalitis, grouped into viral, autoimmune, or unknown/other encephalitis categories, with mortality rates of 8%, 12%, and 5%, respectively. Researchers calculated a modified Rankin Scale score (mRS) on factors associated with good (mRS=0-2) or poor (mRS=3-6) outcome after one year. Factors associated with poor outcome included age 65 or older, immunocompromised state, coma, mechanical ventilation, and acute thrombocytopenia. Unlike some previous studies, MRI findings and seizure activity did not portend a poor outcome. For viral encephalitis, cerebrospinal fluid polymorphonuclear cell count was also strongly associated with poor outcome.
This is one of the first studies to evaluate functional outcome or distant follow-up; however, it has inherent biases related to the retrospective design, and the results are not necessarily generalizable to all hospitals; there might be an underlying referral bias, given the fact that one third of the patients were referred to the center for further evaluation.
This study does suggest aggressive treatment should be pursued, even in patients with severe presentation, given the possibility of favorable recovery.
Bottom line: Advanced age, immunocompromised state, coma, mechanical ventilation, and acute thrombocytopenia portend a worse outcome for patients with acute encephalitis.
Citation: Singh TD, Fugate JE, Rabinstein AA. The spectrum of acute encephalitis: causes, management, and predictors of outcome. Neurology. 2015;84(4):359-366.
