Clinical Implications of the Association between Temporal Bone Tegmen Defects and Superior Semicircular Canal Dehiscence

Objective: To discuss the clinical implications of the association between temporal bone tegmen dehiscence (TD) necessitating surgical correction and the adjacent dehiscent superior semicircular canal (SSCD). Study Design: Retrospective. Setting: Tertiary referral center. Patients: Sixteen patients with idiopathic TD, with or without SSCD, requiring surgical correction. Interventions: Corrective surgery for TD. High-resolution temporal bone-targeted computed tomography. Main Outcome Measures: The impact of the minimal distance between TD and SSCD or the arcuate eminence on the choice of surgical approach to TD. Results: The patients' median age was 58 years and 5 were males. The median body mass index was 31.8 kg/m 2. The average distance from the TD and the SSC was 4.9 mm (range 2.1-14.2 mm). Three of the 14 patients who were operated via a temporal craniotomy to fix a cerebrospinal fluid-leaking TD required plugging of an asymptomatic SSCD due to its close proximity (3-5 mm) to the defect, and two of them had relatively protracted vestibular recuperation. Two patients were operated via a transmastoid approach for sealing a cerebrospinal fluid-leaking TD coexisting with a bilateral asymptomatic SSCD. No patient had a hearing loss. Conclusion: The close proximity of a TD and an SSCD might not allow selective exposure. As a result, asymptomatic SSCD may become symptomatic during TD correction via the temporal craniotomy approach. The need to plug an asymptomatic SSCD that is proximal to a TD should be factored in planning for surgery and rehabilitation. The choice of surgical approach (middle fossa vs. transmastoid) could be influenced by this relationship, especially in cases of bilateral lesions.