Researchers at the Cleveland Clinic report a 23-month-old immunocompetent boy with reactivated herpes simplex virus encephalitis (HSE) after a subtotal hemispherectomy for seizures related to HSE-associated right middle cerebral artery infarction at 7 months of age. The diagnosis had been confirmed by HSV PCR from CSF, and he had completed a 21 day couse of iv acyclovir. Acyclovir and dexamethasone were administered routinely at time of surgery. Fever developed on postoperative day 1 and persisted despite continued acyclovir. CSF HSV PCR was positive for type 1 on postop day 8 and negative day 11. At 3 weeks he was doing well with no seizures and was afebrile. Resected tissue showed multiple infarctions and microglial nodules, consistent with HSE history. 
COMMENT. Reactivation of HSV after HSE is unusual and typically occurs immediately after treatment of a primary encephalitis. Cases with shorter courses of acyclovir may be susceptible. The authors cite one previous case in the literature of HSV reactivation after epilepsy surgery for mesial temporal sclerosis. The primary infection occurred at 16 months of age and reactivation 6 years later after hippocampectomy and gyrus corticotomy, the previous site of herpes infection. 
HSV reactivation should be ruled out by repeated CSF PCR in patients with persistent fever and irritability following epilepsy surgery. Transient immunosuppression complicating perioperative steroid therapy is suggested as a mechanism for HSV reactivation following hemispherectomy.