Background & objective: Acute encephalitis is a major cause of morbidity and mortality worldwide. We analyzed the clinical experience with acute encephalitis at our institution to define the clinical spectrum of this condition in the local population and to identify outcome predictors. Methods: Acute encephalitis cases were identified through ICD9 coding of hospital charts from the period January 1997 through September 2001. Results: There were a total of 164 cases (41.5% adults >15 years, 57.9% males, Mean age= 20.8 +/- 20.6 years). The commonest presenting symptoms were mental status changes (80.5%), fever (79.3%), seizures (59.l%) and headaches (28.7%). CSF sampling was performed in 144 patients of whom 53(36.8%) patients had completely normal CSF. CSF polymerase chain reaction for Herpes simplex virus (HSV) was positive in 16(30.8%) out of 52 cases tested. Seventeen (10.4%) patients died during their hospitalization. Chi-squared univariate analysis showed that adults were more likely to present with CSF protein>45mg/dl (OR= 2.3; p= 0.00; CI= l.6-3.3), CSF total cell count>10cells/ml (OR=2.l; p=0.00; CI=1.5-3.1), CSF lymphocyte predominance (OR=2.3; p=0.00; CI= 0.3-0.6), HSV etiology (OR=1.6; p=0.016; CI=1.1-2.3) and were more likely to die (OR=1.7; p=0.037; CI=0.4-0.9). Multivariate logistic regression analysis showed that the combined presence of CSF protein >45mg/dl, HSV etiology, CSF total cell count >10cells/ml and CSF lymphocyte predominance predicted a poor functional outcome in adults with 70% likelihood (Chi square = 16.3(4), p=0.003). The single most important predictor of poor outcome was elevated CSF protein (>45mg/dl; OR=8, p= 0.006, CI= 1.834.9). Conclusion: Acute encephalitis is a serious illness with a substantial early mortality and should be suspected in all patients presenting with fever and mental status changes. Patients presenting with CSF protein >45mg/dl, HSV etiology, CSF total cell count >10 cells/ml and CSF lymphocyte predominance are more likely to have a poor outcome.
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