Radiological assessment of the sinus tympani: temporal bone HRCT analyses and surgically related findings

Purpose: To evaluate the morphology of the sinus tympani (ST) based on computed tomography (CT) scans (axial view), describing the findings in a cohort of 148 patients (296 ears), and classifying the prevalence according to our ST classification. To evaluate the surgical prevalence based on the type of ST. To calculate the sensibility and positive predictive value (PPV) of high-resolution computed tomography (HRCT) scans for ST involvement by cholesteatoma. Methods: Retrospective review of the radiologic database and surgical reports. Results: In total, 98/296 (33.1 %) middle ears presented a radiologic morphology Type A; 185/296 (62.5 %) middle ears presented a radiologic morphology Type B; 13/296 (4.4 %) middle ears presented a radiologic morphology Type C; HRCT showed a sensibility of 91 %, specificity of 65 %, PPV of 68 % and negative predictive value (NPV) of 90 %. Conclusions: ST shape and depth can influence surgical preference in cholesteatoma surgery. In the case of a shallower ST, an exclusive endoscopic exploration is chosen; whereas in the case of a deeper ST, a retrofacial approach is usually preferred. HRCT scans demonstrated high sensibility and NPV for ST involvement by cholesteatoma.