Latent herpes simplex virus type 1 in human geniculate ganglia

Viral infection, especially by reactivation of herpes simplex virus (HSV) has been considered to be a possible explanation for the pathogenesis of idiopathic peripheral facial nerve palsy (Bell's palsy). We investigated whether the geniculate ganglia of man contain latent HSV type 1 (HSV-1), and compared the frequency of HSV-infected ganglia and that of latently infected neurons in human geniculate ganglia and in trigeminal ganglia. From autopsy specimens of eight adults 15 geniculate ganglia and 16 trigeminal ganglia were examined by means of in situ hybridization and immunohistochemical staining. The HSV-1 genome was detected in 11 of the 15 (71%) geniculate ganglia and in 13 of the 16 (81%) trigeminal ganglia. No HSV antigen was noted in any of the ganglia. The incidence of latently infected neurons was 0.9% in the trigeminal ganglia and 5.3% in the geniculate ganglia. The difference in percentages between the two types of ganglia was significant. Our results suggest that reactivation of latent HSV in the geniculate ganglia is a probable cause of some cases of herpetic stomatitis and of idiopathic peripheral facial nerve palsy.