VESTIBULAR SYMPTOMS IN OTOSCLEROSIS - CORRELATION OF OTOSCLEROTIC INVOLVEMENT OF VESTIBULAR APPARATUS AND SCARPAS GANGLION-CELL COUNT

Although several histopathologic studies have shown otosclerotic invol vement of the vestibular apparatus in patients with otosclerosis, the pathogenesis of vestibular symptoms in otosclerosis remains unknown. A quantitative study of Scarpa's ganglion was performed in 217 temporal bones from 118 subjects with otosclerosis. Review of clinical records revealed an incidence of vestibular symptoms in 11.9% of these subjec ts. Scarpa's ganglion cell counts in temporal bones of subjects with o tosclerosis and vestibular symptoms were lower than counts in temporal bones of subjects with otosclerosis but without vestibular symptoms a nd those of normal subjects. This difference in Scarpa's ganglion cell counts, adjusted for age, between the group with otosclerosis and ves tibular symptoms and a group of normal subjects was highly significant (p = 0.0015), whereas the difference in Scarpa's ganglion cell count between a group with otosclerosis but without vestibular symptoms and a group of normal subjects was not significant (p = 0.53). There was a lso a significant correlation between elevation of the average bone-co nduction threshold and the presence of vestibular symptoms in these su bjects (p = 0.041). The endosteum of the perilymphatic space of the ve stibule and the endosteum of the canal for the superior vestibular ner ve or its cribrose area were the two most common sites of involvement by otosclerosis. However, there was no significant correlation between the presence of vestibular symptoms and otosclerotic involvement of a ny single site or the number of involved sites. Histologic examination of the vestibular nerve fibers and end organs subjacent to otosclerot ic foci demonstrated no obvious degenerative changes. Thus our finding s appear to suggest that the vestibular symptoms present in patients w ith otosclerosis are more common in patients with elevated bone conduc tion thresholds and are correlated with degeneration of the vestibular nerve, which appears to be independent of the severity of otoscleroti c involvement of the vestibular end organs.