Bilateral Superior Semicircular Canal Dehiscence Research Articles

Electrocochleography in the diagnosis of third window conditions.

Superior semicircular canal dehiscence (SSCD) is the best-known and most common presentation of so-called "third window conditions." There are a variety of diagnostic measures and tests for this condition in the current literature, including air-bone gap, vestibular-evoked myogenic potentials, and electrocochleography (EcochG). The purpose of this study was to investigate the diagnostic utility of EcochG and its relationship to air-bone gap in a cohort of patients with confirmed SSCD. We reviewed data from 20 patients (11 female and 9 male subjects, age ranging 21-78 years), with confirmed unilateral or bilateral superior canal dehiscence. In total, 11 patients had unilateral SSCD and 9 patients had bilateral SSCD as determined by high-resolution CT scan. This resulted in the inclusion of twenty-nine ears with superior canal dehiscence and 11 normal ears. Our results indicated that all confirmed SSCD ears presented with an abnormal EcochG SP/AP value and that there was a statistically significant difference between normal and dehiscent ears. There was no statistically significant relationship between air-bone gap and SP/AP ratio in the ears diagnosed with SSCD nor was there a significant difference between dehiscent and normal ears in terms of air-bone gap at three frequencies. These results are consistent with previous studies showing the diagnostic utility of EcochG for this condition and the variability of air-bone gap. While an unexpected air-bone gap continues to be a red flag for SSCD, its absence along with the presence of subjective symptoms is a reasonable indicator for further clinical investigation to include EcochG.

Bilateral Superior Semi-Circular Canal Dehiscence Presenting as Conductive Hearing Loss with Vestibular Symptoms: A Client Centre Case Report

Background: Superior semicircular canal dehiscence (SSCD) is a rare bone defect in the petrous part of the temporal bone. In this syndrome, a third window is created between the middle cranial fossa and the bony labyrinth of the inner ear which can lead to stimulation of the vestibular system by sound. Patients usually have symptoms such as vertigo, imbalance, autophony, pulsatile tinnitus, and aural fullness. The clinical symptoms of this disease vary from person to person.
 The Case: This study reports a case of a rare bilateral SSCD in a 39-year-old woman with imbalance and autophony problems. The audiological findings showed a bilateral mild conductive hearing loss at low frequencies with symptoms of vertigo and torsional nystagmus. The SSCD was diagnosed by computed tomography. Then, the patient underwent bone repair surgery. Auditory and balance tests were performed again after the surgery to evaluate the extent of recovery.
 Conclusion: The SSCD can be diagnosed by using the mentioned test battery. By choosing the appropriate treatment methods and following up of the outcomes, most of the problems of patients with SSCD can be solved.
 Keywords: Superior semicircular canal dehiscence; bilateral; conductive hearing loss

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

To report the frequency of radiographic superior semicircular canal dehiscence (SSCD) and tegmen dehiscence in patients with and without obstructive sleep apnea (OSA). Retrospective matched cohort study. Tertiary care center. 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. Prevalence of SSCD and tegmen dehiscence assessed by two independent reviewers. 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. 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.

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

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. 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. 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). 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.

Bilateral Superior Semicircular Canal Dehiscence without Signs of Vestibular Involvement about a Case

Superior semicircular canal dehiscence (SSCD) is a rare entity recently described whose typical clinical symptomatology is represented by dizziness triggered by a variation of pressure. We reported a case of SSCD which was diagnosed thanks to computed tomography (CT) scan of the petrous bone conducted systematically in front of mixed deafness with normal eardrum. The SSCD was bilateral and was revealed by mixed deafness on the left side and perception deafness on the right with a normal eardrum without the notion of vertigo. The cervical vestibular evoked myogenic potential (cVEMP) and an ultra-high resolution CT scan of the petrous bones in coronal and sagittal sections allowed the diagnosis. The SSCD should be considered in the presence of any conductive or mixed hearing loss with a normal eardrum. The CT scan in coronal and sagittal submillimetric sections allows the diagnosis.

Superior Semicircular Canal Dehiscence Outcomes in a Consecutive Series of 229 Surgical Repairs With Middle Cranial Fossa Craniotomy

Superior semicircular canal dehiscence (SSCD) is the appearance of a third mobile window between the middle fossa and the superior semicircular canal. Surgical management is indicated in patients with persistent and debilitating symptoms. The purpose of this study was to evaluate the association between preoperative variables that may impact postoperative symptomatic resolution. A single-institution retrospective analysis was performed on patients who were surgically treated for SSCD. Patients were divided to different cohorts based on unilateral or bilateral nature of the disease. A P value <0.05 was considered statistically significant. A total of 229 surgical repairs were analyzed. Mean age was 51 years (± 7.8 years), and 55.9% of patients were female. All cohorts were similar with respect to baseline demographics. The most commonly reported preoperative symptoms were tinnitus, dizziness, and autophony. The greatest symptomatic resolution was seen in autophony, internal sound amplification, hyperacusis, and oscillopsia. The unilateral SSCD cohort had significantly higher improvement of autophony (P= 0.003), aural fullness (P= 0.05), tinnitus (P= 0.006), hearing loss (P=0.02), dizziness (P= 0.006), and headache (P= 0.007), compared with the bilateral SSCD cohorts. Among patients with bilateral disease, those with unilateral surgery reported greater symptomatic resolution with respect to hyperacusis (P= 0.03), hearing loss (P= 0.02), dizziness (P= 0.03), and disequilibrium (P < 0.001), than those with bilateral operations. Surgical management of SSCD leads to high rates of postoperative symptomatic improvement. Patients with unilateral SSCD benefit greater symptomatic resolution compared to those with bilateral pathology.

Endoscope-Assisted Superior Semicircular Canal Dehiscence Repair: Single Institution Outcomes.

To compare outcomes of endoscope-assisted middle cranial fossa MCF) repair of superior semicircular canal dehiscence (SSCD) compared to microscopic MCF repair. Retrospective cohort. Tertiary medical center neurotology practice. Retrospective chart review and cohort study of patients who underwent surgical repair of SSCD via MCF approach from 2010 to 2019 at our institution. Patients were categorized according to use of endoscope intraoperatively. Pre- and post-operative symptom number was calculated from 8 patient-reported symptoms. Pre- and post-operative changes in symptom number were assessed using paired t-tests. Single-predictor binary logistic regression was used to compare final reported symptoms between cohorts. Linear regression was performed to assess air-bone gap (ABG) changes postoperatively between cohorts. Forty-six patients received surgical management for SSCD. Of these, 27 (59%) were male and 19 (41%) were female. Bilateral SSCD was present in 14 cases (29%), of which 3 underwent surgical management bilaterally, for a total of 49 surgical ears. Surgery was performed on the right ear in 19 cases (39%) and on the left in 30 cases (61%). Forty ears (82%) underwent microscopic repair while 9 (18%) underwent endoscope-assisted repair. Microscopic and endoscope-assisted MCF repair both demonstrated significantly improved symptom number postoperatively (P < .001 for each). There was no significant difference in change in ABG between the 2 cohorts. On average, patient-reported symptoms and audiometrically-tested hearing improved postoperatively in both groups. While endoscopic-assisted MCF repair has the potential to provide better visualization of medial and downslope defects, repair via this technique yields similar results and is equivalent to MCF repair utilizing the microscope alone.

Superior Semicircular Canal Dehiscence Syndrome Following Head Trauma: A Multi-institutional Review.

To evaluate patients who become symptomatic from superior semicircular canal dehiscence (SSCD) following head trauma. Case series assessing patients presenting with SSCD after a trauma. A case series was completed assessing patients presenting with SSCD after trauma. Data from three academic medical centers were evaluated, including the following: imaging, videonystagmography (VNG)/vestibular evoked myogenic potential (VEMP) testing, audiometric assessment, and surgical repair. Outcome measures included the following: 1) Description of audio-vestibular symptoms, 2) mean pre- and post-operative pure tone average (PTA), word recognition score (WRS), and air bone gap (ABG). A total of 14 patients were included; 86% were male. Approximately 43% were found to have bilateral SSCD on imaging, with 57% of patients pursuing surgical management. The most common presenting symptoms included pulsatile tinnitus (93%), autophony (79%), and hearing loss (64%). Approximately 36% of patients underwent VNG/VEMP testing, with 83.3% of those demonstrating abnormal results. The mean audiometric findings on the symptomatic side included an air-conduction PTA of 38.0 dB, bone-conduction PTA of 24.3 dB, WRS of 81%, and ABG of 17.9 dB. Among patients who underwent surgery (57%), there was no significant change in the air-conduction PTA, bone-conduction PTA, or WRS (P > .05). However, there was an improvement in the ABG (preoperative=22.8 dB versus postoperative=9.7 dB; P=.005). Head trauma may be a potentiating event for SSCD syndrome. This study advances the hypothesis that these patients likely have underlying radiographic SSCD prior to their trauma, and a traumatic event increases in intra-vestibular or intracranial pressures, unmasking SSCD syndrome. 4 Laryngoscope, 131:E2810-E2818, 2021.

Clinical Assessment of Patients with Bilateral Superior Semicircular Canal Dehiscence

Superior semicircular canal dehiscence (SSCD) is caused by a deformity in the arcuate eminence, leading to various vestibular and auditory symptoms that can manifest unilaterally or bilaterally. The aim of the present study was to distinguish the differences in symptoms, treatment options, and outcomes between patients with unilateral and bilateral SSCD. A retrospective medical record analysis was conducted to identify patients with SSCD treated at a tertiary care center from March 2011 to May 2017. The patient demographic data, preoperative symptom presentation, and postoperative outcomes were extracted. Statistical analyses were performed using IBM SPSS Statistics. Fisher's exact tests were computed to investigate the relationships between binary variables, with a significance level of P<0.05. A total of 99 patients with SSCD had been treated at our institution from March 2011 to May 2017. Of these 99 patients, 41 (41.4%) had a diagnosis of bilateral SSCD. Of the 41 patients with bilateral SSCD, 27 (65.9%) were women, and the mean age was 53.6 ± 10.9 years (range, 31.7-73.9). The most common presenting symptom was tinnitus (n= 33; 80.4%) and dizziness (n= 33; 80.4%). Previous trauma to the head correlated with a bilateral SSCD presentation (P= 0.04). Trends were reported between female sex and bilateral SSCD [r(35)= 0.32379; P=0.0506]. Postoperatively, trends were also found, with greater rates of dizziness in patients with bilateral SSCD compared with those with unilateral SSCD (odds ratio, 3.81; P= 0.0659), and less improvement in dizziness (odds ratio, 0.186; P= 0.0627). No other significant differences were found between the symptoms or clinical outcomes and improvements between the bilateral and unilateral cohorts. Bilateral SSCD might result in different clinical symptoms that are more prevalent compared with unilateral SSCD. The findings from the present series of patients with bilateral SSCD suggest that patient symptoms and history are important in the diagnosis of bilateral SSCD and deciding whether 1 or both dehiscences requires surgical intervention.

Case Study: An Uncommon Case of Bilateral Superior Semicircular Canal Dehiscence Associated with Sudden Sensoryneural Hearing Loss

Case Study: An Uncommon Case of Bilateral Superior Semicircular Canal Dehiscence Associated with Sudden Sensoryneural Hearing Loss

P.010 5 layers reconstruction, superior semicircular canal dehiscence repair: our experience and surgical technique

Background: Superior semicircular canal dehiscence (SSCD) is a recently described rare condition. SSCD symptoms include vertigo, oscillopsia, autophony, sound hypersensitivity , and conductive hearing loss. Patients with sever symptoms may require surgical treatment. Tranmastoid and middle fossa (MCF) approaches are common approaches. Methods: We are presenting our experience at the Ottawa Hospital over the last three years. Also we describe our multidisciplinary surgical approach and modalities to localize the SSCD intraoperatively. Demographic data, presenting symptoms, co-morbidities, radiologic imaging, and surgery length were recorded. All patients had hearing and vestibular tests before and after their surgeries. Results: 14 surgeries were performed in 11 patients (three patients had bilateral SSCD). Most patients were males (82%). Age range was 32-68 years. Surgeries were done by a team of a neurosurgeon and a neuro-otologist. Localization of SSCD was done using stereotactic guidance. Five layers’ reconstruction was performed in all patients. All patients had significant improvement in symptoms without sensorineural hearing loss. None of the patients developed post-operative hematoma, infection, seizures, CSF leakage or facial palsy. LOS was 1-2 days. Conclusions: MCF with multi layers reconstruction should be considered as a safe and effective approach in severely symptomatic patients. We demonstrated that this approach has minimal risks especially in regards to sensorineural hearing loss.

The Effects of Vestibular Rehabilitation after Bilateral Superior Semicircular Canal Dehiscence: A Case Report

Background and Purpose: Despite the strong body of evidence for vestibular rehabilitation, research is lacking for effective clinical management of patients with superior semicircular canal dehiscence (SSCD) and endolymphatic hydrops (EH). The purpose of this case report is to describe the effects of physical therapy in the treatment of a patient diagnosed with bilateral SSCD. Case Description: The patient was a 56-year-old woman with a long-standing otologic history involving bilateral SSCD and EH. The patient’s body structure and function impairments include constant headaches, dizziness with head rotation and eye movements, sensitivity to sounds and lights, and instability during gait. Her activity limitations include lower extremity dressing, driving, and playing her flute. Her participation restrictions include taking part in social gatherings, going to church, driving longer than 30 minutes, playing with her dogs, and teaching flute lessons. Interventions: Specific interventions included vestibular habituation and adaptation exercises, balance and gait training, and patient education. Physical therapy services were provided for approximately 11 weeks with a frequency of two times per week. Outcomes: After eleven weeks of physical therapy, the patient made improvements on the Lower Extremity Functional Scale (43/80 to 52/80), the Dynamic Gait Index (19/24 to 24/24), the Dizziness Handicap Inventory (86/100 to 68/100), and the Sharpened Romberg (2 seconds to >30 seconds). The patient improved in all her activity limitations and participation restrictions. She was able to play her flute for 20-minute intervals, play with her dogs, partake in social gatherings, and drive for 5 hours without symptoms. The patient had plans to pursue surgical intervention within the next year. Discussion: For a patient with a complex otologic history and a current diagnosis of bilateral SSCD, vestibular rehabilitation was an effective management option. The information from this case can be used to guide the effective treatment of similar patients diagnosed with vestibular dysfunction.

Transmastoid Approach for Resurfacing the Superior Semicircular Canal Dehiscence with a Dumpling Structure

Background:Superior semicircular canal dehiscence (SSCD) is gradually recognized by otologists in recent years. The patients with SSCD have a syndrome comprising a series of vestibular symptoms and hearing function disorders which can be cured by the operation. In this study, we evaluated the characteristics of patients with SSCD and determined the effectiveness of treating this syndrome by resurfacing the canal via the transmastoid approach using a dumpling structure.Methods:Patients with SSCD, confirmed by high-resolution computed tomography and hospitalized at Beijing Tongren Hospital between November 2009 and October 2012, were included in the study. All of the patients underwent the unilateral transmastoid approach for resurfacing the canal, and received regular follow-up after surgery. Data from preoperative medical records and postoperative follow-up were comparatively analyzed to evaluate the effect of surgery.Results:In total, 10 patients and 13 ears (three left ears, four right ears, three bilateral ears) were evaluated in the study, which included 7 men and 3 women. Different symptoms and distinctive manifestations of vestibular evoked myogenic potential were found in these patients. After surgery, 4 patients had complete resolution, 5 had partial resolution, and 1 patient, with bilateral SSCD, had aggravation. None of the patients suffered from serious complications such as sensorineural hearing loss, facial paralysis, cerebrospinal fluid leakage, or intracranial hypertension.Conclusions:In patients with unilateral SSCD, resurfacing the canal via the transmastoid approach using a dumpling structure is an effective and safe technique. However, more consideration is needed for patients with bilateral SSCD.

Superior canal dehiscence reveals concomitant unilateral utricular loss (UUL)

Conclusion: We report enhanced symmetrical cervical vestibular evoked myogenic potential (cVEMP) but asymmetrical ocular VEMP (oVEMP) responses in a patient with CT-verified bilateral superior semicircular canal dehiscence (SCD) but with acute vestibular syndrome. This implies that absence of unilateral utricular macula function alone is sufficient to cause symptoms of acute vertigo. Acute vertigo should not automatically be presumed to originate from semicircular canal dysfunction. Objectives: To identify the cause of an acute vertigo attack in a patient with bilateral SCD. Methods: The functional state of all peripheral vestibular sense organs was tested using the video head impulse test (vHIT) for all semicircular canals and VEMPs to air-conducted sound (ACS) or bone-conducted vibration (BCV) to test all otolith organs. The cVEMP tested mainly saccular function and the oVEMP mainly utricular function. Results: All semicircular canals showed normal function. The cVEMPs showed enhanced, but symmetrical saccular function. In contrast, oVEMPs showed an enhanced but asymmetric n10 component – it was greatly reduced beneath the left eye, implying decreased function in the right utricular macula. That result was confirmed using very high frequency stimuli which are effective in SCD: 4000 Hz BCV stimuli showed that oVEMP n10 was present beneath the right eye but absent beneath the left eye.

Large Bilateral Internal Auditory Meatus Associated with Bilateral Superior Semicircular Canal Dehiscence

Superior semicircular canal dehiscence and an abnormally wide internal auditory meatus are clinical entities characterized by vestibular and cochlear symptoms. These symptoms are induced by hypersensitivity of labyrinthine receptors secondary to a bone defect of the otic capsule. We report the case of a 41-year-old man with congenital right-sided hearing loss who presented with bilateral superior semicircular canal dehiscence that was associated with wide, bulbous internal auditory meatus and a loss of the bony wall separating the lateral end of the meatus from the cochlea. The patient was experiencing vestibular and cochlear symptoms in the right ear and disabling tinnitus in the left ear. However, he refused all treatment and was lost to follow-up.

Radiographic Evaluation of the Tegmen in Patients With Superior Semicircular Canal Dehiscence

To determine a radiographic association between superior semicircular canal dehiscence (SSCD) and tegmen dehiscence (TD). Retrospective case-control series. Tertiary referral center. Patients seen between 2003 and 2010 with radiographic SSCD were compared with cochlear implant recipient controls. The tegmen and superior semicircular canal were evaluated on computed tomographic temporal bone scans. If detected, the widest point of the SSCD was measured. The tegmen was graded on a 5-point scale. After analysis, a radiographic TD was defined as any single area of absent tegmen greater than 5 mm, multiple areas of absent tegmen, or evidence of meningocele. Age, sex, and body mass index were also noted. Thirty-eight patients with SSCD and 41 cochlear implant controls were identified. Seventy-six percent (29/38) of patients with unilateral or bilateral SSCD had a radiographic TD on at least 1 side compared with 22% (9/41) of the comparison group. Ninety-four percent (7/18) of patients with bilateral SSCD had a TD on at least 1 side. Patients with SSCD had a 10.2 times (p < 0.001) higher odds of having radiographic TD in either ear compared to the controls. Among patients with any SSCD, for every millimeter increase in the width of dehiscence, the relative risk for any TD increased more than 2-fold (odds ratio, 2.5; p = 0.019). Age, sex, and a body mass index greater than 30 did not confound the association between SSCD and TD. There is a strong radiologic association between SSCD and TD, suggesting a similar etiologic process. The tegmen should be carefully evaluated in patients with SSCD. We have also proposed a new system for radiographically grading the integrity of the tegmen.

Bilateral superior semicircular canal dehiscence in a child with sensorineural hearing loss and without vestibular symptoms

To report a rare case of bilateral superior semicircular canal dehiscence (SCCD) in a child. Case report, 11-year-old female patient. Descriptive case report. Audiological findings of bilateral symmetrical low frequency sensorineural hearing loss with ascending curves and bilateral superior semicircular canal dehiscence on a high resolution computed tomography (CAT) scan. The young child presented with bilateral fluctuating hearing loss with no vestibular symptoms. She was found to have bilateral superior semicircular canal dehiscence. We hereby present a rare case of bilateral semicircular canal dehiscence found incidentally on high resolution CAT scan in a young child during work up for bilateral sensorineural hearing loss.

Superior semicircular canal dehiscence and lack of the tympano-ossicular system: Favourable functional aspects of a coincidental finding

AbstractObjectives: Our objectives were to report the functional conditions of superior semicircular canal dehiscence (SSCD) associated with the post-inflammatory lack of tympano-ossicular system. Methods: A 40-year-old male, initially referred for bilateral ear discharge due to a left cholesteatoma and a right unstable ‘intact bridge’ tympanoplasty, underwent a left open mastoidectomy without a tympano-ossicular reconstruction. Two years later, he had a conversion of the ‘intact bridge’ tympanoplasty into an open mastoidectomy without reconstruction on the right side. Moreover, he had a bilateral SSCD diagnosed by means of vestibular evoked myogenic potentials (VEMPs) and high-resolution computed tomography (HRCT). Results: Combination of the absence of the tympano-ossicular system and SSCD resulted in surprisingly good hearing function. Conclusions: The reported bilateral near-to-normal hearing function outlines the possibility of a favourable outcome deriving from the association of two different adver...

The Association Between Semicircular Canal Dehiscence and Chiari Type I Malformation

To investigate the association between semicircular canal dehiscence (SCD) and Chiari type I malformation (CM-I). Retrospective case series. Military tertiary referral center. Adult patients with SCD. Review of records of patients diagnosed as having SCD for the radiologic diagnosis of CM-I and presenting symptoms. The prevalence of CM-I among patients with SCD and the presenting symptoms of patients with SCD with and without a coexistent CM-I. Of 32 patients diagnosed as having SCD, 30 underwent magnetic resonance imaging of the brain. Seven patients (23%; 95% confidence interval [CI], 12%-41%) were found to have a CM-I. Chiari type I malformation was associated with superior SCD in 3 of 26 patients (12%; 95% CI, 3%-30%). Of 10 patients with bilateral superior SCD, 2 (20%; 95% CI, 5%-52%) had a CM-I. Five of 6 patients (83%; 95% CI, 42%-99%) had a CM-I with unilateral or bilateral posterior SCD. Twenty-nine records were reviewed for presenting symptoms, and no significant difference was observed between patients with SCD alone and those with an associated CM-I (P = .09-.64). Among patients with SCD, the prevalence of CM-I is elevated. This association is especially marked in patients with posterior SCD. This finding suggests a relationship between CM-I and SCD, particularly with posterior SCD.

Third mobile window associated with suspected otosclerotic foci in two patients with an air–bone gap

To demonstrate the need for computed tomography imaging of the temporal bone in patients clinically suspected of otosclerosis who present with atypical symptoms or audiological findings. We present two patients with bilateral conductive hearing loss and suspected otosclerosis in whom third mobile window lesions were revealed. The first patient had bilateral large vestibular aqueducts and bilateral fenestral otosclerotic foci. Computed tomography imaging of the second case revealed bilateral superior semicircular canal dehiscence and bilateral cochlear clefts, mimicking an otosclerotic focus in the fissula ante fenestram. Differentiating third mobile window lesions from otosclerosis as the cause of a conductive hearing loss is essential before considering stapes surgery, as such treatment would be unnecessary and potentially harmful.