Evaluation and analysis of the transmission route of sigmoid sinus tinnitus by HRCT of the temporal bone: A retrospective analysis.

Objective: This study aims to analyze anatomical parameters of the transmission route of sigmoid sinus tinnitus (SST) to explore its mechanism and speculate on possible responsible anatomical abnormalities.

Methods: Clinical data were retrospectively collected from SST and sigmoid sinus wall dehiscence (SSWD) patients suggested by temporal bone high resolution computed tomography (HRCT), with and without tinnitus, at the First Affiliated Hospital of Chongqing Medical University from January 2015 to August 2022. Patients were divided into SSWD tinnitus (n = 61), and non-tinnitus (n = 60) groups based on HRCT features. Mimics Medical 22.0 and 3-matic Medical 13.0 software measured curvature of the sigmoid sinus bone wall, defect distribution, related parameters, distance to the tympanic sinus and cochlear window, degree of mastoid pneumatization, temporal bone air chamber surface area, volume, and S/V value. Mechanisms were analyzed by comparing clinical data and imaging anatomical parameters between groups.

Results: The tinnitus group was significantly younger and had more severe low-frequency hearing loss (P = 0.002). The degree of mastoid pneumatization was significantly lower in the tinnitus group (P = 0.032). The volume of the temporal bone air chamber was smaller (P = 0.020), and the S/V value was higher in the tinnitus group (P = 0.001). Bone wall defects in the lower curvature were protective against tinnitus (P = 0.007, OR = 0.071). Larger maximum transverse diameter of the defect increased tinnitus risk (P = 0.030, OR = 1.875). Higher S/V value was also a significant risk factor (P = 0.009, OR = 24.210).

Conclusions: SST patients exhibit significant female and right-sided predominance, with low-frequency hearing loss. Defects in the superior curvature and descending part of the sigmoid groove are more likely to cause tinnitus. Larger transverse diameters and higher S/V values are independent risk factors for tinnitus. Over-pneumatized temporal bones do not facilitate transmission of sigmoid sinus blood flow murmur, highlighting the importance of specific anatomical features in SST development.