Animal studies indicate that active viral replication and necrotizing encephalitis
with diffuse perivascular infiltrates of lymphocytes and maerophages occur in cerebral parenchyma (9,10).
Herpes simplex virus type 1 (HSV-1), in addition to causing recurrent cold sores and corneal infections, may cause a severe necrotizing encephalitis
in children and adults.[1,2] HSV-1 may exist in a latent fashion in trigeminal ganglia. In both experimental animals and humans, HSV-1 is present in a latent state in normal brain tissue.[1,4] Reactivation of HSV may occur due to a variety of stimuli, including fever and exposure to ultraviolet light, or there may be no identifiable cause. Animal studies suggest that HSV reactivation from latency is an efficient multisystem process controlled by neuronal, immune, and viral factors. The exact role of radiation in viral reactivation is not fully established, but the interaction of all 3 cofactors is suspected.