Superior Semicircular Canal Dehiscence: Assessing the Spectrum of Clinical Features and Surgical Outcomes in a Longitudinally Followed up Cohort of 34 Patients

Background: Superior semicircular canal dehiscence (SSCD) is an uncommon and incompletely understood disorder of the temporal bone that arises from a defect in the bony inner ear, commonly over the arcuate eminence where the SSC shallowly underlies the middle fossa floor. The diagnosis was described relatively recently, in part due to the odd symptomatology associated with the creation of a mobile third window that was previously misinterpreted, and few series with longitudinal follow-up have been reported. Correspondingly, our study objective was to review our experience with SSCD, including the typical presentation, operative management, and surgical outcomes in a large, single-institution case series with extensive follow-up.

Methods: Retrospective review of a prospectively maintained institutional database. Patient demographics, presenting symptoms, radiographic features, and surgical outcomes are reported.

Results: Thirty-four SSCD patients underwent 39 surgical treatments by a combined skull base neurosurgery/neurootology team during the study period, November 2001 to May 2017. Twenty were male (59%) and overall median age was 53 years (range: 26–70). Median follow-up was 24 months (range <1–132). Common presenting symptoms included vertigo (73%), autophony (71%), imbalance (71%), hypoacusia (52%), tinnitus (53%), and ear fullness (53%). Tullio (sound-induced vertigo) and Hennebert’s phenomenon (Valsalva-induced vertigo) were positive in 47 and 44%, respectively. Vestibular-evoked myogenic potentials (VEMP) where positive in 97%.

Left-sided dehiscence was more common than right-sided (60 vs. 40%), and 97% of SSCD were approached using a middle fossa craniotomy. Seven patients (19%) had bilateral SSCD, of whom three required bilateral operations. Overall, 37 of 39 SSCD operations resulted in durable resolution of at least 2 major symptoms (95%); 2 patients developed a recurrence requiring reoperation (5%), which was successful in both cases. Complications were rare, and included a delayed seizure at 3 months after surgery in 1 patient (3%), a DVT at 3 weeks after surgery in 1 (3%), and 1 instance of serous otitis media requiring myringotomy and pressure equalizer tube placement (3%). No patient developed a postoperative CSF leak, and there were no mortalities.

Conclusion: SSCD is an uncommon and idiosyncratic disorder, with an odd but relatively characteristic clinical presentation that frequently includes vertigo, autophony, and imbalance, among other otologic phenomena. VEMP testing is a reliable tool, and should be incorporated into the diagnostic work-up whenever possible. Overall surgical results are excellent, with minimal risk of complications, 95% efficacy at first repair, and 100% overall in our series of 39 SSCD followed for a median 24 months. Further prospective follow-up in larger, multicenter cohorts will be required to definitively assess the long-term postoperative outcomes; notwithstanding, our results provide optimistic preliminary evidence that operative repair will provide durable relief for the vast majority of SSCD patients.