Unveiling the importance of the endoscope in the sealing of the superior canal dehiscence syndrome, how we do it.

The superior canal dehiscence syndrome is a pathology that affects the arcuate eminence creating a "third window" between the inner ear and the middle fossa. This condition can lead to symptoms such as hearing loss, autophony, or sound-induced vertigo. Traditionally, surgical treatment has been performed by microscope-assisted temporal craniotomy, but when the dehiscence is in the medial part of the arcuate eminence the bone defect may not be seen. We present case series treated at our institution diagnosed of superior canal dehiscence syndrome involving the medial slope of the arcuate eminence. During surgery, the bone defect could not be visible with traditional microscopic techniques. Nonetheless, by introducing the endoscope with the 0º and 30º optics, the dehiscence could be clearly observed and treated correctly. Our results show a clinical improvement without side effects or complications in the patients undergoing this technique. Endoscope-assisted surgery is a safe procedure and provides a better visualization of medial defects.

Surgical decision-making in superior canal dehiscence syndrome with concomitant otosclerosis.

OBJECTIVE: The diagnosis and management of Superior Canal Dehiscence Syndrome (SCDS) with concomitant otosclerosis can be a challenge. Otosclerosis can mask SCDS symptoms and stapes surgery may reveal or exacerbate vestibular symptoms. Our aim is to present four cases of SCDS with concomitant otosclerosis and thereby informing the reader about the possibility of this dual occurrence and its implications for treatment. CASES: Four patients with SCDS and concomitant otosclerosis are presented. Two patients underwent surgical treatment for both SCDS and otosclerosis and two patients opted for conservative management. OUTCOMES: The main differences between surgically and non-surgically treated cases are the presence of autophony and pressure-induced vertigo and a more severe experience of symptoms in surgically treated cases. Surgically treated cases achieved a sizeable reduction in postoperative air-bone gap and resolution of vestibular symptoms. CONCLUSION: The subjective severity of symptoms in combination with shared decision-making is key in determining the appropriate treatment plan for SCDS and concomitant otosclerosis.

Traumatic Events Preceding the Development of Superior Canal Dehiscence Syndrome.

OBJECTIVE: To describe the features of antecedent head trauma in patients with superior canal dehiscence syndrome (SCDS). STUDY DESIGN: Cross-sectional survey. SETTING: Tertiary referral center. METHODS: An online survey was sent to 450 adult patients who underwent surgical repair for SCDS patients asking questions about the nature of internal or external traumatic events preceding symptoms. RESULTS: One-hundred and thirty-six patients (avg. age, 51.9 years, 62.8% female) completed the survey, of which 61 (44.9%) described either preceding external head trauma (n = 35, 26%), preceding internal pressure event (n = 33, 25%), or both (8, 6%). Of those endorsing external trauma, 22 (63%) described a singular event (head hit by object (n = 8); head hit ground (n = 5); motor vehicle accident (n = 4); assault (n = 2); other (n = 3). One-third experienced loss of consciousness because of the trauma. For those describing internal pressure events (n = 33), the most common events were heavy physical exertion (9, 27%); pressure changes while flying (6, 18%); coughing, nose blowing with illness (5, 15%); childbirth (5, 15%); and self contained underwater breathing apparatus diving events (3, 9%). The interval between trauma and onset of symptoms averaged 5.6 years (SD, 10.7 years). One-third (n = 19) described onset of symptoms immediately after the external trauma or internal pressure event. Symptoms began on the side ipsilateral to the trauma in 91%. Sound- and pressure-induced vertigo/oscillopsia developed more commonly after external trauma versus internal pressure events (68% and 61% vs 44% and 32%, respectively). CONCLUSION: Trauma or internal pressure-related events precede SCDS symptoms in nearly half of cases, with roughly half of preceding events being external.

Patient Sex Mediates the Influence of Patient Age on Superior Canal Dehiscence Repair Outcome.

OBJECTIVE: To investigate the independent and interactive effects of patient age and sex on superior canal dehiscence (SCD) repair outcomes. METHODS: This was a cohort study of consecutive SCD repairs via the middle fossa approach at an institution between 2011 and 2022. We constructed multivariable regression models assessing surgical outcomes with age and sex as the primary predictors. Models controlled for surgery duration, follow-up duration, and relevant surgical and medical history. Subsequently, we repeated each model with the incorporation of an interaction term between patient age and sex. RESULTS: Among 402 repairs, average age was 50 years, and 63% of cases were females. There was a significant interaction between patient age and sex with respect to symptom resolution score (SRS) (adj. ß 0.80, 95% C.I. 0.04-1.56). Older age was associated with lower SRS among females (-0.84, -1.29 to -0.39 point per year) but not significantly associated with SRS among males (0.04, -0.65 to 0.56 point per year). Furthermore, older age independently predicted a greater magnitude of increase in air conduction at 8000 Hz following surgery regardless of sex (adj. ß 2.1, 0.2-4.0 dB per 10-year increase). CONCLUSIONS: This is the first study on the interactive effect between patient age and sex with respect to SCD repair outcomes. Older age predicted poorer symptomatic response among female patients but did not predict symptomatic response among male patients. Furthermore, older age predicted more severe high-frequency hearing loss following SCD repairs among both female and male patients. LEVEL OF EVIDENCE: 3 Laryngoscope, 134:3363-3370, 2024.

The importance of bone density and anatomical structure in superior semicircular canal dehiscence.

OBJECTIVE: This study investigates the importance of bone density, surface area, and diameter of anatomical structures of the superior semicircular canal (SSC), lateral semicircular canal (LSC), posterior semicircular canal (PSC), utricle, and saccule in patients diagnosed with superior semicircular canal dehiscence (SSCD). MATERIALS AND METHODS: The bone density, surface area, and diameter of SSC, LSC, PSC, utricle, and saccule were measured and compared between the SSCD group and control group. Fifteen ears in the SSCD group and 60 ears in the control group were evaluated. Additionally, within the SSCD group, the dehiscent and healthy sides were evaluated independently. RESULTS: SSC's bone density was significantly lower in the SSCD group compared to the control group (p = 0.008). No significant differences were found in surface area and diameter between the groups (p > 0.05). While most of the anatomical structures showed no significant difference in bone density between dehiscent and healthy ears (p > 0.05), SSC bone density was significantly lower in affected ears (p = 0.000) in SSCD group. CONCLUSION: Based on the data obtained in this study, bone density and anatomical structure may be useful in patients diagnosed with SSCD.

Trans-mastoid plugging of superior semicircular canal dehiscence: long-term follow-up.

OBJECTIVE: To evaluate the long-term outcomes of trans-mastoid plugging of superior semicircular canal dehiscence (SSCD), focusing on complicated cases. METHODS: In this cohort study, we included all patients who underwent trans-mastoid plugging of SSCD between 2009 and 2019. We evaluated the symptoms (autophony, sound-/pressure-induced vertigo, disequilibrium, aural fullness and pulsatile tinnitus) before and 1 year after surgery in the medical records. We systematically assessed the current symptoms 6.2 ± 3 years postoperative (range 2.2-12.3 years) using questionnaires sent by post and validated by telephone interviews. We also documented any complications and the need for further procedures. We compared pure tone and speech audiometry before and 1 year after surgery. Finally, the degree of mastoid pneumatisation and mastoid tegmen anatomy were reviewed on preoperative CT scans. RESULTS: We included 24 ears in 23 patients. No complications were recorded, and none required a second procedure for SSCD. Following surgery, oscillopsia and Tullio phenomena resolved in all patients. Hyperacusis, autophony, and aural fullness were also settled in all patients except one. Balance impairment persisted to some degree in 35% of patients. No deterioration over the years was reported regarding the above symptoms. On average, bone conduction pure tone average pre- and 1 year postoperative were 13.7 ± 17 and 20.5 ± 18 dB, respectively (P = 0.002). Air bone gaps were reduced from 12.7 ± 8 to 5.9 ± 6 (P = 0.001). Two patients had a significant sclerotic mastoid, three had a prominent low-lying mastoid tegmen, and two had both. Anatomy had no effect on outcome. CONCLUSION: Trans-mastoid plugging of SSCD is a reliable and effective technique which achieves long-lasting symptom control, even in cases with sclerotic mastoid or low-lying mastoid tegmen.

Third window lesions of the inner ear: A pictorial review.

PURPOSE: Radiographic review of pathologies that associate with third window syndrome. METHODS: Case series and literature review. RESULTS: Eight unique third window conditions are described and illustrated, including superior, lateral, and posterior semicircular canal dehiscence; carotid-cochlear, facial-cochlear, and internal auditory canal-cochlear dehiscence, labyrinthine erosion from endolymphatic sac tumor, and enlarged vestibular aqueduct. CONCLUSION: The present study highlights the characteristic imaging features and symptoms to differentiate third window pathologies for expedient diagnosis and management planning.

Auditory and Vestibular Symptom Improvement With Surgery for Superior Canal Dehiscence Syndrome.

OBJECTIVE: (1) To measure the change in auditory and vestibular symptoms following superior canal dehiscence (SCD) surgery, and (2) to determine differences in clinical features and surgical outcomes between superior canal dehiscence syndrome (SCDS) patients with primarily auditory or vestibular complaints. STUDY DESIGN: Retrospective cohort study. SETTING: Single surgeon series at the tertiary academic medical center from 2002 to 2021. METHODS: Retrospective review of SCDS patients who underwent surgical repair. (1) Patients were administered a standardized symptom questionnaire at preoperative and follow-up visits, and results were compared with paired statistical testing. (2) Patients were divided into 2 cohorts based on either auditory or vestibular chief complaint and differences in demographic, clinical, and outcome variables were examined. RESULTS: Our study included 113 patients with 118 operated ears. Twenty-seven patients (24%) had radiographic bilateral dehiscence. 10/11 auditory symptoms (91%) and 5/8 vestibular symptoms (63%) solicited on the questionnaire improved significantly with surgery, except for nonpulsatile tinnitus, sense of imbalance, positional dizziness, and oscillopsia. Analyses stratified by chief complaint (auditory vs vestibular) revealed overall similar characteristics and surgical outcomes. Patients with chief vestibular complaints underwent surgery at an earlier age (45.5 vs 53.9 years, p < 0.05). CONCLUSION: SCD surgery alleviates a wide range of auditory and vestibular symptoms. Overall, we did not find significant differences between patients with chief auditory versus vestibular complaints, and both groups benefited from surgery. Symptoms are not directly linked to third-window physiology and certain vestibular symptoms may be more likely to persist. Bilateral dehiscence may play an important role in persistent symptoms as well.

Audiometric Outcomes After the Middle Cranial Fossa Repair of Superior Semicircular Canal Dehiscence.

OBJECTIVE: To evaluate the audiometric outcomes after the middle cranial fossa approach (MCF) for superior canal dehiscence (SCD) repair. STUDY DESIGN: Retrospective review. SETTING: Tertiary referral center. PATIENTS: SCD cases presented to a single institution between 2012 and 2022. INTERVENTIONS: The MCF repair of SCD. MAIN OUTCOME MEASURES: Air conduction (AC) threshold (250-8,000 Hz), bone conduction threshold (BC) (250-4,000 Hz), and air bone gap (ABG) (250-4,000 Hz) at each frequency, pure tone average (PTA) (500, 1,000, 2,000, 3,000 Hz). RESULTS: Among 202 repairs, 57% were bilateral SCD disease and 9% had previous surgery on the affected ear. The approach significantly narrowed ABG at 250, 500, and 1,000 Hz. The narrowing of ABG was achieved by both decreased AC and increased BC at 250 Hz, but mediated primarily by increased BC at 500 Hz and 1,000 Hz. Among cases without previous ear surgery, mean PTA remained in the normal hearing range (mean: preop, 21 dB; postop, 24 dB) and clinically important hearing loss (PTA increased by ≥10 dB) after the approach was noted in 15% of cases. Among cases with previous ear surgery, mean PTA remained in the mild hearing loss range (mean: preop, 33 dB; postop, 35 dB) and clinically important hearing loss after the approach was noted in 5% of cases. CONCLUSION: This is the largest study to date examining the audiometric outcomes after the middle cranial fossa approach for SCD repair. Findings of this investigation support that the approach is effective and safe with long-term hearing preservation for most.

Ankle Audiometry: A Clinical Test for the Enhanced Hearing Sensitivity for Body Sounds in Superior Canal Dehiscence Syndrome.

INTRODUCTION: The aim of this study was to develop a clinical test for body sounds' hypersensitivity in superior canal dehiscence syndrome (SCDS). METHOD: Case-control study, 20 patients affected by SCDS and body sounds' hypersensitivity and 20 control matched subjects tested with a new test called ankle audiometry (AA). The AA consisted of a psychoacoustic hearing test in which the stimulus was substituted by a controlled bone vibration at 125, 250, 500, and 750 Hz, delivered at the medial malleolus by a steel spring-attached bone transducer prototype B250. For each subject, it was defined an index side (the other being non-index), the one with major symptoms in cases or best threshold for each tested frequency in controls. In 3 patients, the AA was measured before and after SCDS surgery. RESULTS: The AA thresholds for index side were significantly lower in SCDS patients (115.6 ± 10.5 dB force level [FL]) than in control subjects (126.4 ± 8.56 dB FL). In particular, the largest difference was observed at 250 Hz (-16.5 dB). AA thresholds in patients were significantly lower at index side in comparison with non-index side (124.2 ± 11.4 dB FL). The response obtained with 250 Hz stimuli outperformed the other frequencies, in terms of diagnostic accuracy for SCDS. At specific thresholds' levels (120 dB FL), AA showed relevant sensitivity (90%) and specificity (80%) for SCDS. AA did not significantly correlate to other clinical markers of SCDS such as the bone and air conducted hearing thresholds and the vestibular evoked myogenic potentials. The AA thresholds were significantly modified by surgical intervention, passing from 119.2 ± 9.7 to 130.4 ± 9.4 dB FL in 3 patients, following their relief in body sounds' hypersensitivity. CONCLUSION: AA showed interesting diagnostic features in SCDS with significantly lower hearing thresholds in SCDS patients when compared to healthy matched subjects. Moreover, AA could identify the affected or more affected side in SCDS patients, with a significant threshold elevation after SCDS surgery, corresponding in body sounds' hypersensitivity relief. Clinically, AA may represent a first objective measure of body sounds' hypersensitivity in SCDS and, accordingly, be an accessible screening test for SCDS in not tertiary audiological centers.

Postoperative Pneumolabyrinth Following the Middle Cranial Fossa Approach for Superior Semicircular Canal Dehiscence Repair, 2014-2020.

OBJECTIVE: The present study investigates risk factors and clinical outcomes of postoperative pneumolabyrinth following the middle cranial fossa approach for superior semicircular canal dehiscence repair, a complication that has not been documented previously. STUDY DESIGN: Retrospective cohort study. SETTING: Tertiary/quaternary care referral center. METHODS: We conducted a retrospective review of 332 middle cranial fossa procedures from 2014 to 2020 at a tertiary/quaternary care institution. Upon identifying pneumolabyrinth cases from postoperative computed tomography temporal bone scans, we conducted multivariable logistic regression analysis to explore demographic and clinical factors that were independently linked to this complication. We also compared the rates of postoperative symptoms among patients with different grades of pneumolabyrinth. RESULTS: We identified 41 (12.3%) pneumolabyrinth cases. Patients with older age, higher preoperative pure tone average, and frank dehiscence were at higher risk for pneumolabyrinth. Furthermore, patients with pneumolabyrinth reported significantly higher rates of postoperative dizziness and exhibited significantly greater pure tone average and air-bone gap postoperatively as compared with patients without pneumolabyrinth. Finally, higher-grade pneumolabyrinth was associated with increased rates of postoperative hearing loss, and grade III pneumolabyrinth was associated with higher rates of postoperative tinnitus vs grade I and II cases. CONCLUSION: Pneumolabyrinth following the middle cranial fossa approach was associated with poor clinical outcomes, including dizziness and auditory impairment. Old age, high preoperative pure tone average, and frank dehiscence were risk factors for this complication. The highlighted parameters may be important to note when considering this approach as a treatment option and while monitoring postoperative recovery.

Matched Cohort Study of Radiographic Superior Semicircular Canal Dehiscence and Tegmen Dehiscence and Obstructive Sleep Apnea.

OBJECTIVE: To report the frequency of radiographic superior semicircular canal dehiscence (SSCD) and tegmen dehiscence in patients with and without obstructive sleep apnea (OSA). STUDY DESIGN: Retrospective matched cohort study. SETTING: Tertiary care center. PATIENTS: Adults with OSA and fine-cut computed tomographic scans including the temporal bone were matched to patients without OSA by age, sex, and type of computed tomography (protocol, scanner type, slice thickness). Ears with otologic surgery or temporal bone tumors were excluded. MAIN OUTCOME MEASURES: Prevalence of SSCD and tegmen dehiscence assessed by two independent reviewers. RESULTS: The average body mass index of the OSA patients was 29.2 kg/m 2 with an average apnea-hypopnea index of 36.8. The control group had an average body mass index of 26.2 kg/m 2 . Of the 352 temporal bones, 34 (9.7%) had SSCD in the OSA cohort versus 37 (10.5%) in the control group ( p > 0.05). Seven OSA patients (25.6% of those with SSCD) had bilateral SSCD versus 8 controls (27.6% of those with SSCD; p > 0.05). The majority (87.3%) of dehiscences involved the temporal lobe, with the remaining involving the superior petrosal sinus or both. Of the 352 OSA ears, 90 (25.6%) had a tegmen dehiscence versus 95 (27.0%) in the control group ( p > 0.05). Neither group had a laterality preference for SSCD or tegmen dehiscence. CONCLUSION: The prevalence of radiographic SSCD and tegmen dehiscences in OSA patients does not significantly differ from age- and sex-matched controls. This is in contrast to a previous case-control study finding patients with symptomatic SSCD to have higher rates of OSA. This may suggest that the effect size of OSA on SSCD prevalence may be limited despite OSA being a risk factor for elevated intracranial pressure.

Vestibular Migraine Confounds Management of Superior Canal Dehiscence Syndrome.

OBJECTIVE: To investigate the prevalence of vestibular migraine (VM) in a cohort of patients with radiologic confirmation of superior canal dehiscence (SCD) and to compare management of superior canal dehiscence syndrome (SCDS) in patients with and without comorbid VM. STUDY DESIGN: Retrospective review of a SCD database. SETTING: University-based tertiary medical center. PATIENTS: Ninety-one patients identified with SCD from 2009 to 2017. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Coincidence of VM and SCD, and resolution of symptoms. RESULTS: Ninety-one patients with SCD met the inclusion and exclusion criteria. VM was diagnosed in 36 (39.6%) patients. Of those receiving medical therapy for VM alone, five (45.5%) reported symptom resolution, five (45.5%) reported partial improvement, one (9.1%) had no change, and none worsened. Fifteen patients (41.7%) were treated with both surgery (for SCD) and medical therapy (for VM). Seven (46.7%) reported symptom resolution, seven (46.7%) reported partial improvement, and one (6.7%) worsened. There was no statistically significant difference in symptom resolution between SCD + VM patients who were treated medically compared with those treated with medical therapy and surgery (p = 0.951). There was no significant difference in symptom resolution after surgery between SCD + VM and SCD-only cohorts (p = 0.286). CONCLUSIONS: This is the first study describing the incidence of VM in a cohort of patients with SCDS. The symptoms of VM confound those of SCDS and unrecognized or undertreated VM may contribute to surgical failure in SCDS. Therefore, we recommend a high index of suspicion for VM in patients with SCDS and a trial of medical therapy in the setting of suspected VM.

Assessment of Metabolic Markers and Osteoporosis in 250 Patients with Superior Semicircular Canal Dehiscence Treated With Middle Fossa Craniotomy.

BACKGROUND: Superior semicircular canal dehiscence (SSCD) is caused by bony defects in the osseous shell of the arcuate eminence separating the labyrinth and the intracranial space. This pathologic third window causes hydroacoustic transmission resulting in debilitating symptoms. We examine the pathophysiologic association between metabolic markers, previous medical history, and SSCD symptoms before and after middle fossa craniotomy (MFC) treatment. METHODS: This study was conducted between March 2011 and September 2020 with patients with SSCD who underwent MFC. We used a Fisher test to compare variables, including bilateral SSCD, second surgery, ear anomaly, osteoporosis, arthritis, vitamin D, and preoperative/postoperative symptoms, and others. Point-biserial correlation analysis was performed to test correlations between continuous variables and categorical variables. RESULTS: A total of 250 patients with SSCD underwent MFC repair. There was significant postoperative resolution in all symptoms (P < 0.0001). Laboratory 25-hydroxyvitamin D values correlated with preoperative aural fullness (rpb= 0.29; P = 0.03), and preoperative disequilibrium (rpb= -0.32; P = 0.02). Serum calcium values correlated with preoperative hearing loss (rpb= 0.16; P = 0.02). Osteoporosis history (n = 16; 6%) was more prevalent in female patients (P = 0.0001), associated with higher levels of preoperative hearing loss (odds ratio, 4.56; P = 0.02) and higher postoperative hearing loss resolution (odds ratio, 2.89; P = 0.0509). CONCLUSIONS: Certain metabolic markers may predict SSCD presentation before and after surgery. Previous history of osteoporosis, autoimmune conditions, or arthritis may play a role in SSCD pathophysiology and can help predict clinical outcomes. Future evaluation should take metabolic laboratory values and acquire an exact medical history.

Long-Term Outcomes of Round Window Reinforcement for Superior Semicircular Canal Dehiscence Syndrome.

OBJECTIVE: To report long-term patient reported outcome measures (PROMs) after standardized round window rein-forcement (RWR) with thin cartilage and perichondrium for superior semicircular canal dehiscence syndrome (SSCDS). METHODS: Cross-sectional survey in 2020 and retrospective longitudinal study of outcomes at 3 months, 1 year, and last follow-up after 28 consecutive RWRs. Endpoints were the last follow-up for PROMs and 1 year postoperatively for audiometry and cVEMP. RESULTS: At the last follow-up (mean 2.4 years postoperatively), improvement was reported for 19/28 ears (68%) in symptoms overall; for 17/27 ears (63%) in auditory symptoms, and for 12/24 (50%) in vestibular symptoms. Nine ears (32%) required further surgery. No major complications occurred. On the group level, postoperative improvement at 3 months declined significantly for auditory and vestibular symptoms over time, and stayed stable beyond 1 year. Improved ears had on average 2.9 years follow-up. Improvement correlated significantly with SSCD length, and was associated with contralateral dehiscence. Thirteen ears (46%) had another potential cause of vestibular symptoms. This group showed significantly less improvement. Audiometric test results did not predict PROMs. CONCLUSIONS: Since long-term outcomes do not compare with those reported for plugging and repair, RWR is not suggested as a first line intervention for SSCDS. Considering the stable rates of improvement on average 2.9 years postoperatively and the absence of major complications, RWR may be an alternative to plugging or repair in fragile patients who do not accept the risk of complications with more invasive surgery, and who accept that results may deteriorate over time.

Evaluation of the transmastoid plugging approach for superior semicircular canal dehiscences: a retrospective series of 30 ears.

PURPOSE: The classical surgical approach for superior semicircular canal dehiscences (SSCD) is via the extradural middle cranial fossa. This pathway is used to resurface or to plug the SSC. In this paper, we present long-term data on an alternative route: the transmastoid pathway. The predictive factors for a successful surgery are equally presented in this paper. METHODS: Thirty reports of patients operated between September 2007 to January 2020 were analysed. SSCD was confirmed by the association of concordant complaints, audiometric data, cervical vestibular evoked myogenic potentials (cVEMP) responses and computerized tomography findings. Before and after surgery, the following factors were analysed: auditory and vestibular subjective symptoms, Tullio phenomenon, pure-tone audiometry thresholds for air and bone conduction, air-bone gap, cVEMP threshold, and computerized tomography data, for instance the size of the dehiscence. RESULTS: The follow-up is 21 months on average. The transmastoid approach significantly improves all symptoms (although there were less probing results for the vestibular symptoms). Objectively, we can observe, a closure of the audiometric air-bone gap on the low frequencies and an improvement in the cVEMP. The only correlation that was identified was between the preoperative cVEMP results and the postoperative air conduction. CONCLUSIONS: The originality of this study is the long postoperative follow-up. It allowed us to evaluate the symptoms in the long term and to determine a predictive factor of postoperative complication, which has not yet been described until today.The transmastoid plugging technique is safe and effective. Additional long-term data with a larger cohort are needed to confirm our results and correlation studies.

Hearing Outcomes of Transmastoid Plugging for Superior Canal Dehiscence Syndrome by Underwater Endoscopic Surgery: With Special Reference to Transient Bone Conduction Increase in Early Postoperative Period.

OBJECTIVE: To investigate the influence on hearing of transmastoid plugging of the superior semicircular canal accompanied with membranous superior canal transection by underwater endoscopic ear surgery (UWEES) for the superior semicircular canal dehiscence syndrome. STUDY DESIGN: Retrospective case review. SETTING: Tertiary referral center. PATIENTS: Seven patients underwent plugging with membranous superior canal transection with UWEES from 2017 to 2019. INTERVENTION: Bone conduction (BC) thresholds (250, 500, 1000, 2000, 4000 Hz) were repetitively examined in early postoperative period. MAIN OUTCOME MEASURES: Subjective symptoms and pure-tone audiometry. RESULTS: Transient BC threshold increase was detected in all cases in early postoperative period and hearing levels were ameliorated in 1 to 2 months. The mean maximum BC threshold elevations (dB) during the early postoperative period (within 1 mo) and the postoperative stable hearing period (after 2 mo) were 18.6 and 2.9 at 250 Hz, 24.3 and 8.6 at 500 Hz, 26.4 and 8.6 at 1000 Hz, 28.6 and 7.1 at 2000 Hz, and 30.0 and 0.8 (except for scale-out cases) at 4000 Hz. respectively. The mean maximum BC thresholds in the early period were significantly elevated compared with those in the stable period at each frequency (p < 0.01). CONCLUSIONS: Hearing outcomes of transmastoid plugging with transection of the membranous superior canal by using UWEES were found favorable in a long-term follow-up. However, it caused transient reversible hearing loss in all cases. The BC increase in early postoperative period may not cause permanent hearing loss but improvement for the surgical technique may still be necessary.