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.[3] 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.[5] Animal studies suggest that HSV reactivation from latency is an efficient multisystem process controlled by neuronal, immune, and viral factors.[6] The exact role of radiation in viral reactivation is not fully established, but the interaction of all 3 cofactors is suspected.