Experimental herpes simplex virus and cytomegalovirus labyrinthitis.

Herpes simplex virus (HSV) and guinea pig cytomegalovirus (GPCMV) were inoculated into the middle ear of guinea pigs. The routes of passage of middle ear infection to the inner ear are hematogenous and/or via the cochlear windows. The presence of GPCMV inclusion body-bearing cells within the cochlea strongly suggests the hematogenous route, as in some animals the inner ear does not show cell infiltration and precipitate. When viral infection approaches the cochlear windows, the first morphological changes observed are the presence of precipitate in the inner ear fluids and the appearance of macrophages. These changes are particularly marked near the windows. Direct invasion of the infection into the inner ear after rupture of the round window membrane results in hemorrhage and marked cell infiltration. Inclusion body-bearing cells are found scattered within the exudate. Possible emperipolesis is frequently observed. No cells or tissues can escape involvement in viral labyrinthitis. Fibrosis and ossification eventually occur. Anomaly of the cochlea, the mirror image of the organ of Corti, was observed in the offspring of a guinea pig in whom cytomegalovirus was inoculated into the inner ear.