[Experimental viral labyrinthitis--an immunohistochemical investigation of the cochlear lesion]

Pathogenesis of viral labyrinthitis is still poorly understood despite the dimension of clinical problem. This study was undertaken in order to elucidate the pathogenesis of viral labyrinthitis by the immunohistochemical investigations of infected cochleas. HVJ (Sendai virus) and mumps virus have been used to create an animal model of viral labyrinthitis. The cochleas of adult guinea pigs with intralabyrinthine inoculation of virus through the round window membrane and with intravascular injection of virus were investigated by histopathological and immunohistochemical techniques (immunofluorescent and Avidin-Biotin-Peroxidase Complex method). Control animal received only the culture medium. Histopathologically, fibrosis of scala tympani, vacuolization of stria vascularis, cell infiltration in perilymph were observed in the animals with intralabyrinthine inoculation, whereas no significant changes were observed in those with intravascular injection. Immunohistochemical studies revealed that viral antigen of HVJ was found in stria vascularis (6/11), Reissner's membrane (5/11), Organ of Corti (2/11) and viral antigen of mumps was found in stria vascularis (3/11), Reissner's membrane (1/11), Organ of Corti (1/11) in inoculated side of cochlea. In animal with intravascular injection, viral antigen of HVJ was found in stria vascularis (4/6), Organ of Corti (1/6) and viral antigen of mumps was found in stria vascularis (5/18), Organ of Corti (2/18). Cochleas of control animal showed no evidence of viral antigen. Viral antigen of both viruses were found in stria vascularis, Reissner's membrane, and Organ of Corti. Of these, Stria vascularis showed stronger affinity to these viruses. The results of intravascular injection indicate that endolymphatic labyrinthitis may ensure as a result of viremia.