Transmastoid approach for surgical management of superior semicircular canal dehiscence

Abstract

Congress Abstract The large variety of audiovestibular symptoms due to superior semicircular canal dehiscence (SSCD) can be well tolerated by most patients or sometimes assume disabling features to require surgical repair. Even though different types of strategies, including canal re-roofing or plugging, either through the middle cranial fossa (MCF) or transmastoid (TM) route, have been proposed as canal approaching, the optimal treatment has not been established yet. We report our experience concerning SSCD surgical management via a TM approach, assessing postoperative outcomes. We conducted a retrospective review of the clinical records of all the patients (17 subjects, 10 men and 7 women; mean age, 50.2 years; range age, 19-67 years) who underwent canal surgery at our institution from 2005 to 2012 to relieve their incapacitating symptoms. These subjects were selected from a pool of 172 patients identified as having SSCD at our institution over a 10-year period (January 2003 to August 2012). Criteria for inclusion were the presence of SSCD on HRCT-reformatted images along the plane of the SSC and at least one suggestive sign of dehiscence (sound- and/or pressure-evoked eye movements or lowered thresholds of VEMPs). Each patient underwent the same diagnostic workup including pure-tone audiometry completed by impedance audiometry, VOG bedside examination, analysis of VEMPs, and temporal bone HRCT scans with multiplanar reconstructions. Instrumental data contributed to lead the choice of the side to treat in bilateral cases (n = 6). Two patients had the dehiscence at the superior petrosal sinus. Although in two cases a craniotomy was performed (one occlusion via MCF approach and one re-roofing through a zygomatic root approach), eight patients underwent canal plugging and seven patients had resurfacing of the canal roof using different materials via the TM route. Intraoperative 3D ultrasound neuronavigation provided better localization of the bony defect in one case, while the aid of a piezoelectric device facilitated the cortical bone graft harvesting from the mastoidectomy in another case. Mean follow-up period was 10 months (range, 2-19 months). Complications included a transitory sensorineural hearing loss in five cases and seroma in two. Auditory symptoms resolved in 80% of patients almost immediately after surgery, whereas vestibular symptoms and signs of all the patients, except two subjects (treated with canal plugging), tended to improve over time. Four patients experienced a transitory BPPV episode. Postoperative VEMPs recording revealed normalization of threshold in all the patients who underwent electrophysiologic testing. All subjects treated with canal resurfacing showed an intact vestibulo-ocular reflex at the postoperative video-head impulse test in the horizontal plane, revealing no vestibular hypofunction. According to our experience concerning this initial series of cases, both principal surgical techniques represent reliable and effective solutions to relieve patients of SSCD symptoms. Advantages and disadvantages of the MCF and TM approach will be discussed, and our surgical strategy will be reviewed.