[An experimental study of herpes simplex virus infection in the facial nerve]

In the experimental animals, the author succeeded in establishing the pathogenicity of herpes simplex virus (HSV) in the facial nerve. KOS strain of HSV type 1 was inoculated to the tongue or the auricle of the balb/c mouse previously treated by intraperitoneal injection of cyclophosphamide. Between 4 and 12 days after the inoculation, the facial nerves were resected and submitted to histopathological and immunohistochemical investigations. Inflammatory changes were mainly observed in the geniculate ganglion and its proximal portion of the facial nerve irrespective of the site of the inoculation. In the same sites, HSV antigens were proved. The viral geniculate ganglionitis was induced in 21.4% of the animals inoculated to the tongue, 30.0% of those to the unilateral auricle, and 37.5% of those to the bilateral auricles respectively. This experiment demonstrated that HSV inoculated in the site innervated by sensory component of the facial nerve could affect the geniculate ganglion and its neighboring portion. These results presented a substantial support of the viral hypothesis in the etiology of Bell's palsy.