The etiology of idiopathic sudden sensorineural hearing loss - Experimental herpes simplex virus infections of the inner ear

Hypothesis: Experimentally induced herpes simplex virus type 1 (HSV-1) laby rinthitis provides a suitable model for idiopathic sudden sensorineural hea ring loss (ISSHL). Background: Viral labyrinthitis has been postulated to play a role in the p athophysiology of ISSHL. Circumstantial evidence is painting at members of the herpes virus family. Experimental viral labyrinthitis elicited by vario us virus families leaves a virus-specific pattern of cochlear damage. Herpe s viruses provide the best matching pattern in the distribution of cochlear damage when compared with ISSHL postmortem cochlear histopathology. Methods: Herpetic viral labyrinthitis was induced in guinea pigs using peri lymphatic inoculation with HSV-1. A control group was inoculated with the c ulture medium only. Infection was confirmed by the measurement of HSV antib odies. Hearing was monitored. Cochlear damage was evaluated by light and el ectron microscopy. Results: In all HSV-1 inoculated animals, rapid loss of hearing occurred. S eroconversion took place, but no systemic manifestations of herpetic infect ion were observed. The control group showed no cochlear or systemic symptom s. When comparing cochlear histopathology in ISSHL to experimental viral HS V-1 labyrinthitis, strong similarities were found: degeneration of the stri a vascularis, destruction of the organ of Corti, loosening of the tectorial membrane, and inflammatory changes in neural structures. Conclusions: Based on clinical and histopathologic characteristics, experim ental HSV-1 labyrinthitis provides a suitable model of ISSHL.