Multiple Otosclerotic Foci: Impact on Cochlear Function

Objective: Quantify and illustrate the location of otosclerosic foci using morphologic images and 3D reconstruction. Evaluate the impact of multiple otosclerotic foci on hearing loss. Method: We investigated our histopathological collection to identify all the temporal bones with: 1) oval window otosclerosis (n = 200), 2) oval window and multiple otosclerotic foci (n = 35), 3) oval window plus cochlear otosclerosis (n = 133), and 4) oval window foci with cochlear and multiple other otosclerotic foci (n = 31). Foci were tabulated for each specimen. Cochlear function (hearing) and morphology (otosclerotic foci quantity and location) were compared. Results: Of 574 temporal bones with evidence of otosclerosis, 67 had multiple foci. Ectopic foci were found in the internal auditory canal, the peri-carotid area, semicircular canals and anterior to the cochlea. There was no influence of the number of foci (not involving the cochlea) on hearing loss and cochlear morphology. Conclusion: This is the first systematic evaluation of the number and location of ectopic multiple otosclerotic foci. As previously reported, there is a relationship between cochlear otosclerosis and sensorineural hearing loss, however the addition of other foci does not affect hearing.