There are 2-4 cases per million per year. Perhaps a third of herpes encephalitis cases are due to primary HSV infection while two-thirds are due to reinfection or reactivation of a latent HSV agent. Adults who develop herpes encephalitis invariably HSV Type 1 is responsible. In neonatal encephalitis, which is primarily due to intrapartum infection, HSV Type II is the most common agent. The clinical syndrome reflects the remarkable localization to the oribital, frontal, and temporal lobe area where early personality changes, bizarre behavior, hallucinations followed by seizures, ephasiasis, and hemaporesis.
Spinal fluid is abnormal.
It may contain red blood cells as well as white blood cells. Neuroimaging, in particular MRI, shows a distinctive pattern. Untreated, herpes encephalitis has a very high mortality and morbidity. Current treatment involves acyclovir 10 mg per kg 3 x per day IV for a minimum of two weeks. It is a prodrug selectively phosphorylated by the virus by a virus coded enzyme thymamine kinase.