Introduction: This study aimed to analyze the predictability of temporal bone (TB) fracture-associated hearing loss by applying a detailed classification separating individual injury of the cochlea, vestibule, and semicircular canals (SCC).
Methods: In this retrospective study, patients with otic capsule-violating (OCV) fractures were further classified as OCV-C(VS) when the cochlea was involved regardless of vestibule or SCC involvement, OCV-V(S) when the vestibule was involved regardless of SCC involvement, and OCV-S when the fracture only involved SCC. Hearing changes were compared by applying the above-mentioned classification, and TB fracture-induced facial palsy was also analyzed.
Results: A total of 119 patients were included. Patients with OCV fractures had significantly worse bone conduction (BC) and air conduction (AC) thresholds (59.1 ± 25.3 and 87.0 ± 29.5 dB) than those with otic capsule-sparing (OCS) fractures (20.1 ± 17.9 and 36.5 ± 21.9 dB; p < 0.001 for each comparison). The BC and the AC thresholds of OCV-C(VS) (77.5 ± 11.0 and 114.2 ± 14.3 dB) and OCV-V(S) (69.3 ± 27.7 and 98.0 ± 22.2 dB) were significantly higher than OCV-S (40.1 ± 22.9 and 62.1 ± 25.6 dB; p < 0.001 for each comparison). The BC hearing thresholds were not significantly improved in the last pure tone audiometry when compared for total, OCV, or OCS cases. The AC threshold significantly improved in OCS cases. In a considerable number of cases with facial palsy, causative fracture lines involved the geniculate ganglion or tympanic segment without the involvement of the otic capsule. Most cases showed significant improvement; however, recovery was limited in cases with obvious fallopian canal disruption.
Conclusions: The cases with sole involvement of SCC had significantly better hearing thresholds than those with cochlear or vestibule involvement, even in OCV fracture cases.
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