Adult herpes simplex encephalitis: fifteen years' experience

Herpes simplex encephalitis (HSE) is the most frequent cause of sporadic necrotizing encephalitis in adults. The aim of this study is to describe the characteristics of HSE and the factors influencing its outcome.

Retrospective study of patients diagnosed with HSE in a tertiary care teaching hospital over a 15-year period. Diagnosis was based on a consistent clinical profile for HSE, plus either a PCR-positive CSF HSV study or consistent brain neuroimaging findings. Patients were divided into 2 groups according to the modified Rankin Scale: good outcome (Grades <=2) and poor outcome (Grades >=3).

Thirty-five patients were included. Mean age was 53.9 years. More than half presented febricula or fever, headache, disorientation, behavioral changes, decreased level of consciousness, or neurological deficit. CSF glucose concentration was normal in all patients and WBC count was normal in 8 (23%). PCR for HSV was positive in 92% and cranial MRI was suggestive of HSE in 100% of patients. Mortality was 8.6%. In relation to outcome, age (OR=1.079; 95% CI, 1.023-1.138) and serum albumin level at admission (OR=0.87; 95% CI, 0.794-0.954) were independent prognostic factors at discharge. At 6 months, days of fever after initiation of acyclovir therapy (OR=1.219; 95% CI, 1.046-1.422) and serum albumin level at admission (OR=0.917; 95% CI, 0.87-0.967) were independent prognostic factors.

Normal brain MRI or detection of low CSF glucose concentration requires consideration of diagnoses other than HSE. Age, serum albumin level at admission, and days of fever after initiation of acyclovir therapy were independent prognostic factors of the disease.