Interaction effect of tegmen tympani and superior semicircular canal statuses on the thickness of the roof of the glenoid fossa: a cross-sectional descriptive study.

PURPOSE: Homogeneous development of temporal bone structures is explained by their ontogenic origin; tegmen tympani (TT) and superior semicircular canal (SSC) are related with the glenoid fossa at the temporomandibular joint (TMJ). Therefore, our objective was to determine a possible relationship between TT status (dehiscence or integrity) and the roof of the glenoid fossa (RGF) thickness; SSC status has also been considered. METHODS: This cross-sectional descriptive study was conducted in two tertiary hospitals on 95 patients (109 ears) presenting hypoacusia, facial palsy, vertigo, tinnitus, and other single or combined symptoms, and submitted to a thin-section multidetector-row computed axial tomography (CT) scan. RESULTS: A significant interaction effect of TT × SSC statuses on RGF thickness was found (p = 0.049). A significant difference in RGF thickness was found only for SSC integrity status between TT integrity and TT dehiscence (p = 0.004). The TT dehiscence increased the risk for RGF dehiscence 12.047 times (p = 0.002). CONCLUSIONS: There is an interaction effect of the statuses of both TT and SSC on the thickness of the RGF, instead of an independent effect of the TT status. When RGF dehiscence is found, TT and SSC statuses should be assessed, to discard associated dehiscences.

Association Between Tegmen Tympani Status and Superior Semicircular Canal Pattern.

OBJECTIVE: Detecting and quantifying the possible association between tegmen tympani (TT) status and superior semicircular canal (SSC) pattern. DESIGN: Observational study. SETTING: Study conducted in three tertiary Spanish hospitals. PATIENTS: Nonselected consecutive patients of all ages (607 temporal bones). INTERVENTIONS: Thin-section multidetector row computed axial tomography (CAT scan) of the temporal bones. MAIN OUTCOME MEASURE: Thickness of SSC bone coverture adjacent to the middle fossa, and TT status as a dichotomous variable: dehiscence (TTD) or integrity (TTI). RESULTS: The observed SSC patterns were dehiscence (3.79%), papyraceous or thin (11.20%), normal (76.77%), thick (4.94%), and pneumatized (3.29%). The observed TT statuses were TTD (10.87%) and TTI (89.13%). TTD was associated with SSCD and papyraceous patterns, and TTI percentages were higher in normal and thick patterns (χ2 = 11.102; p = 0.001). The TTD probability was estimated as a function of SSC pattern and age by a multivariate binary logistics regression model (χ2 = 45.939; p < 0.001). CONCLUSION: SSC pattern was significantly associated with TT status. Age influenced this association. The risk for TTD increased by 4.1% per each year of increasing age, did not differ significantly for normal and thick patterns, and increased 12 times and 20 times for papyraceous and SSCD patterns, respectively.