The spectrum of acute encephalitis: causes, management, and predictors of outcome.

OBJECTIVE: To describe and analyze etiologies, clinical presentations, therapeutic management, and outcomes of patients with acute encephalitis and identify outcome predictors.
METHODS: We conducted a retrospective review of patients diagnosed with acute encephalitis at Mayo Clinic Rochester between January 2000 and December 2012. On the basis of the final diagnosis, the patients were categorized into 3 groups: viral encephalitis, autoimmune encephalitis, and encephalitis of unknown/other etiology. Multivariate logistic regression analysis was used to analyze factors associated with good (modified Rankin Scale scores of 0-2) or poor (scores of 3-6) outcome at hospital discharge.
RESULTS: We identified 198 patients (100 [50.5%] men and 98 [49.5%] women) with a median age of 58 years (range 41.8-69). Etiologies included viral infection (n = 95, 48%), autoimmune (n = 44, 22%), and unknown/others (n = 59, 30%). Good outcome at discharge was achieved by 48 patients (50.5%) with viral encephalitis, 17 (40.5%) with autoimmune encephalitis, and 32 (54.2%) with unknown/other etiologies. Mortality rates were 8%, 12%, and 5% in each of the 3 categories, respectively. On multivariate regression analysis, the factors that were associated with poor outcome were age 65 years or older (p = 0.0307), immunocompromised state (p = 0.0153), coma (p = 0.0062), mechanical ventilation (p = 0.0124), and acute thrombocytopenia (p = 0.0329). CSF polymorphonuclear cell count was also strongly associated with poor outcome in viral encephalitis (p = 0.0027).
CONCLUSIONS: Advanced age, immunocompromised state, coma, mechanical ventilation, and acute thrombocytopenia portend a worse prognosis in acute encephalitis. In contrast, the etiology of encephalitis, development of seizures or focal neurologic deficit, and MRI findings were not associated with clinical outcomes.