Correlation Between Vestibular Disorders and Superior Semicircular Dehiscence on High-resolution Computed Tomography at Tam Anh Ho Chi Minh General Hospital.

Objective: Superior semicircular canal dehiscence (SSCD) is a pathologic condition within the inner ear characterized by various vestibular manifestations. Numerous studies have reported an incidence rate of SSCD ranging from 3.6% to 9% in the general population. The objective of this medical study was to evaluate the prevalence of superior SSCD and investigate its correlation with vestibular symptoms among patients who underwent high-resolution computed tomography (HRCT) scans. To the best of our knowledge, there is limited research and awareness regarding SSCD in Vietnam. In addition, the secondary aim of our investigation is to assess the prevalence of SSCD in Vietnam and compare it with findings from previous studies worldwide. Methods: This retrospective study was conducted at Tam Anh Ho Chi Minh General Hospital from March 2022 to February 2024. Medical records and HRCT scans of the patients were collected. Patients were categorized into two groups: those with and without vestibular disorders. SSCD was defined as the absence of bone overlying the superior semicircular canal facing toward the dura of the middle cranial fossa. Statistical analysis was performed to determine the correlation between vestibular symptoms and the presence of SSCD. Results: A total of 362 patients (including 151 men and 211 women) were recruited. The prevalence of SSCD was 10.2% according to the HRCT scan results. The study found that 18.33% of patients with vestibular disorders had SSCD on HRCT scans, whereas only 6.2% of patients without vestibular disorders exhibited SSCD, indicating a significant association (p-value <0.001). Conclusions: These findings highlight the importance of considering SSCD as a potential etiology in patients presenting with vestibular symptoms and emphasize the diagnostic utility of HRCT.

Minor's syndrome: Dehiscence of the superior semicircular canal. A case report.

Superior semicircular canal (SSC) dehiscence syndrome, also known as Minor syndrome, is a rare condition characterized by vestibular and cochlear symptoms linked to a defect in the bony roof of the SSC. The prevalence is estimated at 0.5%, with a male predominance. Dehiscence may result from abnormal bone development, becoming symptomatic due to minimal trauma or pressure changes. Clinical presentation varies based on dehiscence size and location, with dizziness and oscillatory movements triggered by pressure changes or loud sounds being common symptoms. Other manifestations include conductive hearing loss due to the formation of a ``third window'' in the inner ear. Diagnosis typically involves computed tomography, distinguishing SSCDS from otosclerosis. Surgical treatment is reserved for cases of disabling vestibular pathology, often involving sealing the dehiscence through various approaches.

Superior semicircular canal dehiscence in relation with the superior petrosal sinus: our experience, surgical management and systematic review of literature.

PURPOSE: Most of Superior Semicircular Canal Dehiscence (SSCD) are located in the apical region of the SSC. However, in a small number of cases, it may be situated in the medial wall, causing the SSC to contact with the superior petrosal sinus (SPS). The aim of this study is to describe four patients with SSCD involving the superior petrosal sinus (SSCD-SPS) and to perform a review of the literature. METHODS: Observational retrospective study of patients diagnosed of SSCD-SPS in a tertiary referral center. A systematic review was made, identifying 7 articles in the literature. Clinical presentation, complementary test (pure-tone audiometry, PTA; vestibular evoked myogenic potential, VEMP; computed tomography, CT), therapeutic management and outcomes were reported. RESULTS: Four new cases of SSCD-SPS are reported, in three of them a transmastoid plugging was performed. 54 patients with SSCD-SPS (57 dehiscences) were reported in the literature. The most frequent symptoms were aural pressure (57.41%) and vertigo provoked by pressure/Valsalva (55.55%). Conductive hearing loss was the most common finding in PTA (47.37%). Abnormally low thresholds were observed in 59.46% of reported VEMP. Transmastoid approach was used in ten cases, middle fossa approach in four, round window reinforcement in one, and occlusion of the SPS using coils in two. CONCLUSIONS: Within SSCD, we have encountered a rare subtype characterized by its medial wall location in close proximity to the SPS. This subgroup needs special consideration as it has shown its own distinct characteristics. Regarding therapeutic management, we advocate a transmastoid approach.

Superior semicircular canal dehiscence postoperative outcomes: a case series of 350 repairs.

BACKGROUND: Superior Semicircular Canal Dehiscence (SSCD) is a dehiscence of the otic capsule which normally lies over the superior semicircular canal. This database constitutes the largest series of SSCD patients to date. OBJECTIVE: To determine what preoperative factors, if any, contribute to postoperative outcomes and evaluate symptom resolution in a large SSCD patient cohort. METHODS: A single-institution, retrospective chart review collected patient demographics, intraoperative findings, and pre-and postoperative symptoms. Fisher's exact t-test was performed for unpaired categorical variables, with a significance level of p < 0.05. RESULTS: 350 SSCD repairs were performed. The median age was 52 years (range: 17-86 years, ± 6.4 years), and the median follow-up duration was 4.6 months (range: 0.03-59.5 months, ± 6.8 months). Preoperative hearing loss was significantly associated with female sex (p = 0.0028). The most reported preoperative symptoms were tinnitus (77.4%), dizziness (74.0%), autophony (66.3%), amplification (63.7%), and disequilibrium (62.6%). Between patients who received unilateral versus bilateral SSCD repair, the greatest postoperative symptomatic resolution was seen in autophony (74.9%, p < 0.001), amplification (77.3%, p = 0.00027), hyperacusis (77.4%, p = 0.023), hearing (62.9%, p = 0.0063), and dizziness (54.6%, p < 0.001) for patients with unilateral SSCD repair. CONCLUSION: Surgical repair via the middle cranial fossa approach can significantly resolve auditory, vestibular, and neurological symptoms of patients with SSCD. Although this is one of the largest single-institution SSCD studies to date, future multi-institutional, prospective studies would be beneficial to validate these results.

Comparing Approaches for Repair of Superior Semicircular Canal Dehiscence.

OBJECTIVE: Compare outcomes for subjects who underwent middle cranial fossa (MCF) or transmastoid (TM) repair of superior semicircular canal dehiscence (SSCD). STUDY DESIGN: Retrospective cohort study. SETTING: Quaternary-care, academic neurotology practice. METHODS: Subjects who underwent MCF or TM repair of SSCD between December 1999 and April 2023 were identified. Main outcome measures included demographic data, length of surgery and hospital stay, clinical presentation, and audiometric testing. RESULTS: Ninety-three subjects (97 ears) who underwent surgery for SSCD met inclusion criteria: 58.8% (57) via MCF, 39.2% (38) via TM, and 2.0% (2) via TM + MCF. Median operative time was shorter for the TM (35) compared to the MCF (29) approach (118 vs 151 minutes, P < .001). Additionally, median hospital stays were shorter for TM (36) compared to the MCF (56) approach (15.3 vs 67.7 hours, P < .001). Overall, 92% (49/53) of MCF and 92% (33/36) of TM surgeries resulted in an improvement or resolution of one or more symptoms (P = .84). There was no significant preoperative to postoperative change in the median air conduction pure-tone average (PTA), air-bone gap, or word recognition score in both the MCF and TM groups (P > .05). Improvements of >10 dB in the pre- to postoperative absolute change in bone conduction PTA were noted in 3 subjects in the MCF group and 4 subjects in the TM group (P = .49). CONCLUSION: The TM approach for SSCD demonstrates shorter operative times and length of hospital stay. The TM and MCF approaches have comparable audiometric and clinical outcomes.

Evaluation of clinical predictors of postoperative outcomes in tegmen defect patients with and without concurrent superior semicircular canal dehiscence and cerebrospinal fluid leak.

OBJECTIVES: Tegmen and superior semicircular canal defects have been well studied, yet the factors contributing to their onset and progression are widely debated. The clinical utility of intraoperative intracranial pressure measurements has yet to be tested. This report aims to use intraoperative opening pressure and concurrent superior semicircular canal dehiscence (SSCD) to analyze factors influencing disease course and clinical outcomes in patients with tegmen dehiscence. METHODS: A retrospective analysis of 61 patients who underwent tegmen defect repair was performed. Multiple variables of interest including body mass index (BMI), presence of SSCD, presence of dural venous sinus stenosis, opening pressure, and acetazolamide therapy use were recorded. The cohort was divided into those with or without concurrent SSCD and those presenting with or without cerebrospinal fluid (CSF) leak for analysis. RESULTS: A linear relationship between opening pressure and BMI (p = 0.009) was noted; however, intraoperative opening pressure was not associated with disease outcome. Concurrent SSCD was present in 25 % of patients, while 62 % presented with CSF leak. The concurrent SSCD group exhibited higher opening pressure, higher likelihood of having dural sinus stenosis, and higher likelihood of being discharged on acetazolamide. The CSF leak group had higher likelihood of obstructive sleep apnea and persistent symptoms. CONCLUSIONS: In patients undergoing tegmen defect repair, concurrent SSCD suggests increased disease severity. The presence of preoperative CSF leak predicts persistent symptoms following repair. BMI is linearly correlated with intracranial pressure in these patients.

Lumbar Drain Use during Middle Fossa Approaches for Nonneoplastic Pathology of the Skull Base.

Introduction The middle fossa craniotomy (MFCs) is commonly utilized for spontaneous cerebrospinal fluid (CSF) leaks, encephaloceles, and superior semicircular canal dehiscence (SSCD). This study compares postoperative outcomes of MFCs with and without LD use. Methods A retrospective cohort study of adults over the age of 18 years presenting for the repair of nonneoplastic CSF leak, encephalocele, or SSCD via MFC from 2009 to 2021 was conducted. The main exposure of interest was the placement of an LD. The primary outcome was the presence of postoperative complications (acute/delayed neurologic deficit, meningitis, intracranial hemorrhage, and stroke). Secondary outcomes included operating room (OR) time, length of stay, recurrence, and need for reoperation. Results In total, 172 patients were included, 96 of whom received an LD and 76 who did not. Patients not receiving an LD were more likely to receive intraoperative mannitol ( n = 24, 31.6% vs. n = 16, 16.7%, p = 0.02). On univariate logistic regression, LD placement did not influence overall postoperative complications (OR: 0.38, 95% confidence interval [CI]: 0.05-2.02, p = 0.28), CSF leak recurrence (OR: 0.75, 95% CI: 0.25-2.29, p = 0.61), or need for reoperation (OR: 1.47, 95% CI: 0.48-4.96, p = 0.51). While OR time was shorter for patients not receiving LD (349 ± 71 vs. 372 ± 85 minutes), this difference was not statistically significant ( p = 0.07). Conclusion No difference in postoperative outcomes was observed in patients who had an intraoperative LD placed compared to those without LD. Operative times were increased in the LD cohort, but this difference was not statistically significant. Given the similar outcomes, we conclude that LD is not necessary to facilitate safe MCF for nonneoplastic skull base pathologies.

Impact of superior semicircular canal dehiscence on cochlear implant audiologic outcomes.

PURPOSE: Determine whether adult cochlear implant users with radiographic superior semicircular canal dehiscence experience clinically significant differences in audiological outcomes when compared to cochlear implant users with normal temporal bone anatomy. MATERIALS AND METHODS: Retrospective, single institution review. Adult, post-lingual deaf patients implanted between 2010 and 2020. Inclusion criteria included age 18 years or older, available preoperative computed tomography imaging, and preoperative and postoperative AzBio audiological data for at least 6 months of cochlear implant use. Preoperative and postoperative AzBio Sentence Test scores were compared between patients with normal temporal bone anatomy and those with radiographic superior semicircular canal dehiscence or near dehiscence. RESULTS: 110 patients met inclusion criteria. Mean AzBio score for normal temporal bone anatomy group improved from 35.2 % (SD 28.2) preoperatively to 70.3 % (SD 25.7) postoperatively, an improvement of 35.1 % (SD 28.6). Mean AzBio score for near dehiscent temporal bone anatomy group improved from 26.6 % (SD 28.9) preoperatively to 64.5 % (SD 30.6) postoperatively, an improvement of 37.9 % (SD 27.9). Mean AzBio score for dehiscent temporal bone anatomy group improved from 26.3 % (SD 20.4) preoperatively to 65.1 % (SD 27.6) postoperatively, an improvement of 38.7 % (SD 26.9). Utilizing the one-way analysis of variance test, there was no significant difference in audiologic outcomes between the three groups. CONCLUSIONS: Patients with complete or near complete radiographic superior canal dehiscence at the time of cochlear implantation achieve similar improvements in speech perception scores compared to normal anatomy adult cochlear implant users.

Diagnostic Yield of Patients Undergoing Evaluation of Possible Superior Canal Dehiscence.

OBJECTIVE: To characterize the diagnostic yield of patients undergoing evaluation for superior canal dehiscence syndrome (SCDS), and identify alternative conditions diagnosed in patients suspected of, but not ultimately diagnosed with, SCDS. METHODS: Diagnostically undifferentiated adult patients suspected of having SCDS were identified between 2016 and 2021 at a tertiary academic medical system. Patients were categorized by diagnostic testing, radiographic superior semicircular canal (SSC) abnormality, symptoms, evaluating clinician specialty, operative intervention, and diagnosis. Differences among groups were assessed for statistical significance. RESULTS: Of 1242 candidate patients, 477 met inclusion criteria-evaluation by a clinician with SCDS on their differential diagnosis prior to diagnostic imaging. The mean (SD) age was 53.0 (15.0) years and 70.6% were female. A total of 364 patients underwent subsequent diagnostic imaging, and among these, 164 (45.1%) had a radiographic SSC abnormality with 99 (27.2%) receiving a diagnosis of SCDS (two cases of "near dehiscence syndrome"). One third (33.3%) of patients with SCDS underwent operative repair. Most clinicians with the initial suspicion for SCDS were otolaryngologists (90.6%), who had greater diagnostic yield than clinicians from other specialties (22.2% vs. 6.7%, p = 0.012). Patients not diagnosed with SCDS alternatively received 21 unique diagnoses and 52.1% (138/265) were not definitively diagnosed with any condition. CONCLUSIONS: This study characterizes the diagnostic incidence, or yield, of newly identified radiographic SSC abnormalities (45.1%) and SCDS (27.2%) among people suspected of having SCDS. Considerable overlap in presentation between SCDS and other conditions exists, and there is need for improvement in efficiently diagnosing patients with SCDS and audio-vestibular complaints in general. LEVEL OF EVIDENCE: III Laryngoscope, 2024.

Superior semicircular canal dehiscence: a radiological and clinical study.

Aim: to assess radiologically the prevalence of SSCD with its clinical presentations and its relationship with age. Methods: a prospective cohort study carried out on 200 consecutive patients (400 temporal bones). Radiological evaluation was performed using High Resolution Computed Tomography (HRCT) with measurement of thickness of bone covering superior semicircular canal (SCC), height and diameter of SSC. Results: Two hundred patients (400 temporal bones) were involved. The mean thickness ± SD, the mean diameter ± SD and the mean height ± SD were 1.38 ± 0.80 mm, 0.94 ± 0.26 mm and 10.91 ± 2.39 mm respectively. The prevalence of SSCD and predehiscence were 1% and 14% respectively. The commonest symptom encountered was autophony (48.3%). When the SSC thickness, diameter and height were compared with the age of patients, statistically significant differences were detected. The highest diameter, lowest height and lowest thickness were found in patients aged from 54 to 72 years. Thickness of bony layer covering SSC was found to be the most validated measurement for differentiation between cases with positive and negative symptoms with the highest sensitivity and specificity. Conclusion: The prevalence of SSCD and predehiscence varied among the studies. Autophony is the commonest symptom usually encountered. The condition is acquired rather than congenital. The thickness of bone covering SCC is the most validated measurement in differentiation between cases with positive and negative symptoms.

The History of Superior Semicircular Canal Dehiscence: A Bibliometric Analysis.

OBJECTIVE: The treatment and understanding of superior semicircular canal dehiscence (SSCD) has seen significant developments over the past 25 years. Bibliographic analysis can provide insight into the evolution of research as well as highlight emerging areas. Reviewing a large volume of publications provides valuable insights into the citation patterns and collaborations of research groups. This study seeks to offer a comprehensive historical overview of SSCD and leading authors. DATABASE REVIEWED: Web of Science Core Collection. METHODS: A bibliometric analysis of the current literature on SSCD was conducted. A performance analysis and science mapping of the top 100 most cited articles was completed using a citation analysis. Two independent reviewers evaluated articles for relevance and adjugated by a third reviewer. Author and institution networks were examined. RESULTS: Seven hundred ninety-one articles on the topic of SSCD were identified. The top 100 articles spanned over 23 years from 1998 to 2019 and were published in 30 different journals. The top 100 articles were cited 8253 times in literature. The document contents revealed 233 keywords and 238 author keywords. The articles were authored by a total of 291 authors, with only 4 single-authored documents. CONCLUSIONS: SSCD has been highly researched in aspects of symptomatology, diagnosis, and treatment, as indicated by many highly cited articles that relate. However, the production of highly cited articles on SSCD displays a significant decrease after 2013, with only 17 of the top cited articles published since then.

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.

First-Side and Second-Side Repair of Bilateral Superior Canal Dehiscence.

OBJECTIVE: Bilateral superior canal dehiscence (SCD) may warrant surgeries on both sides. With repairs of unilateral SCD as reference, we investigate the comparative effectiveness of first-side and second-side repairs, in hopes of establishing knowledge that can guide clinical decision-making pertaining the appropriateness of second-side surgeries. METHODS: Middle fossa SCD repairs at an institution between 2011 and 2022 were analyzed. Multivariable regression models assessed symptom resolution and audiometric improvement with surgery cohort (unilateral SCD repair vs. first-side repair vs. second-side repair) as the primary predictor. All models controlled for patient age, sex, surgery duration, prior ear surgery, and follow-up. RESULTS: A total of 407 repairs (180 unilateral SCD, 172 first-side, and 55 second-side repairs) were analyzed. The rates of overall symptom improvement for auditory and vestibular symptoms were as follows: 81% and 67% for unilateral SCD repairs; 73% and 54% for first-side repairs; and 43% and 51% for second-side repairs, respectively. Compared with first-side repairs, which resolved auditory symptoms at similar rates (aOR 95% C.I. 0.36-1.07) but resolved vestibular symptoms at significantly lower rates (aOR 95% C.I. 0.35-0.93) compared with unilateral SCD repairs, second-side repairs resolved auditory symptoms at significantly lower rates (aOR 95% C.I. 0.10-0.51) but resolved vestibular symptoms at similar rates (aOR 95% C.I. 0.45-2.01). CONCLUSIONS: Careful consideration of perioperative symptomatology may inform the appropriateness of second-side surgeries. If auditory symptoms persisted following first-side surgeries, second-side surgeries are less likely to yield resolution. If vestibular symptoms persisted following first-side repairs, second-side repairs may lead to resolution at similar rates as first-side repairs. LEVEL OF EVIDENCE: 3 Laryngoscope, 134:1882-1888, 2024.

Association of the superior semicircular canal and tegmen tympani dehiscences and its relationship with the pneumatisation of the temporal bone.

PURPOSE: To analyse the degree of pneumatisation of the temporal bone when there is an association between dehiscence of the superior semicircular canal and dehiscence of the tegmen tympani. MATERIALS AND METHODS: We analysed a retrospective CT study of 124 selected cases. A single inclusion criterion was applied: the presence of a dehiscence of the tegmen tympani. On the other hand, the degree of temporal pneumatisation was assessed by axial and coronal planes, and has been divided into the following grades O, I, II and III, according to the status and relationship of the mastoid, the bony labyrinth, the petrous segment of the carotid canal and sigmoid sinus. RESULTS: Of the 124 cases studied, 35 (28.2%) presented both dehiscences. In 26 of the 35 (47.3%), grade II pneumatisation, 4 (14,8%), grade I, and 5 (11,9%) grade III was observed, with a statistically significant relationship (p < 0.001). On the other hand, we did not find a significant relationship when relating both dehiscences in any age or sex group. However, when relating the degree of pneumatisation to sex, among those with grade III pneumatisation, the proportion of men (52.4%) was significantly higher than that of women (47.6%) (p = 0.017). CONCLUSION: We have detected a statistically significant relationship between the coexistence of grade II pneumatisation and the presence of both dehiscences in the temporal bone.

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.

An evidenced-based diagnostic tool for superior semicircular canal dehiscence syndrome.

Purpose: To construct a symptoms-based prediction tool to assess the likelihood of superior canal dehiscence (SSCD) on high-resolution CT. Materials and methods: Mathematical modeling was employed to predict radiologic evidence of SSCD at a tertiary neurotology referral center. Results: A total of 168 patients were included, of which 118 had imaging-confirmed SSCD. On univariate analysis significant predictors of SSCD presence were: sound/pressure-induced vertigo (p = 0.006), disequilibrium (p = 0.008), hyperacusis (p = 0.008), and autophony (p = 0.034). Multivariate analysis enabled a 14-point symptom-weighted tool to be developed, wherein a score of ≥6 raised the suspicion of SSCD (≥70% likelihood of being present), R2 = 0.853. Conclusions: The likelihood of SSCD on CT scan can be determined with a high degree of certainty based on symptoms recorded at presentation. Using the evidenced-based diagnostic tool validated herein, a score ≥6 with any symptom combination justifies ordering a CT scan.

Superior semicircular canal dehiscence and subsequent closure induces reversible impaired decision-making.

Background: Vestibular loss and dysfunction has been associated with cognitive deficits, decreased spatial navigation, spatial memory, visuospatial ability, attention, executive function, and processing speed among others. Superior semicircular canal dehiscence (SSCD) is a vestibular-cochlear disorder in humans in which a pathological third mobile window of the otic capsule creates changes to the flow of sound pressure energy through the perilymph/endolymph. The primary symptoms include sound-induced dizziness/vertigo, inner ear conductive hearing loss, autophony, headaches, and visual problems; however, individuals also experience measurable deficits in basic decision-making, short-term memory, concentration, spatial cognition, and depression. These suggest central mechanisms of impairment are associated with vestibular disorders; therefore, we directly tested this hypothesis using both an auditory and visual decision-making task of varying difficulty levels in our model of SSCD. Methods: Adult Mongolian gerbils (n = 33) were trained on one of four versions of a Go-NoGo stimulus presentation rate discrimination task that included standard ("easy") or more difficult ("hard") auditory and visual stimuli. After 10 days of training, preoperative ABR and c+VEMP testing was followed by a surgical fenestration of the left superior semicircular canal. Animals with persistent circling or head tilt were excluded to minimize effects from acute vestibular injury. Testing recommenced at postoperative day 5 and continued through postoperative day 15 at which point final ABR and c+VEMP testing was carried out. Results: Behavioral data (d-primes) were compared between preoperative performance (training day 8-10) and postoperative days 6-8 and 13-15. Behavioral performance was measured during the peak of SSCD induced ABR and c + VEMP impairment and the return towards baseline as the dehiscence began to resurface by osteoneogenesis. There were significant differences in behavioral performance (d-prime) and its behavioral components (Hits, Misses, False Alarms, and Correct Rejections). These changes were highly correlated with persistent deficits in c + VEMPs at the end of training (postoperative day 15). The controls demonstrated additional learning post procedure that was absent in the SSCD group. Conclusion: These results suggest that aberrant asymmetric vestibular output results in decision-making impairments in these discrimination tasks and could be associated with the other cognitive impairments resulting from vestibular dysfunction.

Computed tomography approximated superior semicircular canal dehiscence size and location and their association with clinical presentation.

OBJECTIVE: This study investigates the relationship of superior semicircular canal dehiscence (SSCD) size and location with patient symptomatology and audiometry. METHODS: We retrospectively reviewed SSCD cases presented to a tertiary institution between 2011 and 2022. Dehiscence length and width measured on high-resolution temporal bone computed tomography imaging were used to calculate an approximate dehiscence area (ADA). Dehiscence location was classified employing a six-grade system. Multivariable regression analyses were performed with symptomatology and audiogram metrics as outcome variables and ADA and dehiscence location as the primary covariates of interest. RESULTS: A total of 402 SSCD were included in the analysis. Controlling for patient age, sex, dehiscence laterality, and location, greater ADA was independently associated higher rates of autophony (aOR 1.39; 95% C.I. 1.14-1.71; P = 0.004) and hyper-amplification (aOR 1.39; 1.14-1.70; P = 0.004). Additionally, dehiscences with greater ADA exhibited significantly lower bone conduction threshold at 500 Hz (adjusted ß -1.75, P = 0.006) and 1000 Hz (adjusted ß -1.61, P = 0.018) and significantly wider air-bone gap at 500 Hz (adjusted ß 2.22, P < 0.001) and 1000 Hz (adjusted ß 1.00, P = 0.039). Dehiscence location was not independently associated with any outcome variable examined when accounting for dehiscence size. CONCLUSION: The size of dehiscence is more independently related to clinical presentations than the anatomical location of the dehiscence in the superior semicircular canal. Greater dehiscence size is associated with symptomatology and audiometry consistent with more severe bone conduction hyperacusis.