Latent superior canal dehiscence syndrome unmasked by stapedotomy for otosclerosis

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.

Preoperative Evaluation of Otosclerosis: A National Survey of Otologists

OBJECTIVE

Describe practice patterns in preoperative assessment for stapedectomy.

STUDY DESIGN

Survey.

SETTING

Tertiary referral center.

SUBJECTS

Active members of the American Neurotologic Society and American Otologic Society.

INTERVENTION

Survey.

MAIN OUTCOME MEASURES

Percent of respondents performing preoperative testing with acoustic reflexes (ARs), electrocochleography, vestibular evoked myogenic potentials, and computed tomography (CT). Further analysis of those not ordering routine CT to determine whether imaging would be ordered for previous ear surgery, vestibular complaints, childhood hearing loss, AR inconsistent with otosclerosis, possible advanced otosclerosis, or atypical complaints, including autophony. Further subgroup analysis based on years in practice and practice setting (private versus academic).

RESULTS

Most respondents (56.5%) had practiced more than 15 years and worked in academic settings (69.4%). Rates of routine use of preoperative AR, vestibular evoked myogenic potential, and electrocochleography were 80, 4.7, and 0%, respectively. There were no significant differences based on time in practice or practice settings. For CT, 35.3% reported routine use with a statistically significant difference between academic and private practice respondents (42.4% versus 19.2%, p = 0.040). For CT contingent on specific clinical factors, only AR inconsistent with otosclerosis showed a statistically significant difference between academic and private practice providers (85.3% versus 57.1%, p = 0.020).

CONCLUSION

Most otologists routinely obtain AR before stapedectomy. Academic providers more commonly order CT routinely and for AR inconsistent with otosclerosis. Most respondents not ordering routine CT ordered imaging in specific clinical scenarios. Overall, there is a high level of consistency in preoperative testing regardless of practice setting or time in practice.

Incidence of Concomitant Semicircular Canal Dehiscence With Otosclerosis

Objective

The concurrence of otosclerosis and superior semicircular canal dehiscence (SSCD) presents a diagnostic challenge and failure to differentiate between these 2 diagnoses results in mischaracterization and unsuccessful surgery. The objective of this study is to identify the incidence of SSCD in patients who have computed tomography (CT) evidence of otosclerosis.

Study Design

Retrospective chart review.

Setting

Tertiary referral hospital.

Patients

Adults with CT scan of the temporal bone diagnosed with radiological unilateral or bilateral fenestral otosclerosis from January 1995 to April 2018.

Methods

Retrospective review of patient imaging from a multi-center tertiary-referral health system from January 1995 to April 2018. Imaging was reviewed to quantify the incidence of SSCD among patients with CT-diagnosed bilateral fenestral otosclerosis. Poor quality imaging was excluded from review.

Results

One-thousand two-hundred eight patients (1214 CT scans) were identified with otosclerosis, of which 373 were diagnosed with fenestral otosclerosis (663 ears) with imaging of sufficient quality for review. This population was predominantly female (57.2%) with bilateral fenestral otosclerosis (78%). Of these, 23 ears (3.5%) had definitive evidence of SSCD, with an additional 15 ears (2.3%) with possible radiographic evidence of SSCD. There was no significant difference in laterality between the SSCD and otosclerosis.

Conclusions

Among 373 patients with fenestral otosclerosis per CT temporal bone imaging at a tertiary referral hospital, as many as 8.3% of patients had radiographic evidence of SSCD. Given this incidence, it continues to be important to consider SSCD when diagnosing and treating otosclerosis.

Outcomes of Stapedotomy in Patients with Concomitant Otosclerosis and Superior Semicircular Canal Dehiscence: Should a Radiographic Third-Window Be a Contraindication to Stapes Surgery?

OBJECTIVE

Review surgical outcomes of stapedotomy in patients with concomitant otosclerosis and superior semicircular canal dehiscence.

STUDY DESIGN

Retrospective case review.

SETTING

Tertiary referral center.

PATIENTS

Patients with otosclerosis and radiographic superior semicircular canal dehiscence undergoing stapedotomy between 2008 and 2020.

INTERVENTION

Stapedotomy.

MAIN OUTCOME MEASURES

Pre- and postoperative hearing and unmasking of third-window symptoms. Hearing was measured by air conduction (AC) and bone conduction (BC) pure-tone averages (PTA), air-bone gap (ABG), and word recognition scores (WRS). Third-window symptoms included hyperacusis, autophony, sound- or pressure-induced vertigo, imbalance, or oscillopsia.

RESULTS

Twenty patients with otosclerosis and radiographic superior semicircular canal dehiscence underwent stapedotomy, 13 primary and 7 revision. Mean AC PTA was 49.3 dB preoperatively and 35.6 dB postoperatively (p = 0.0077), while the ABG improved on average from 23.9 to 9.68 dB (p < 0.0001). The ABG improved to ≤10 dB in 12/20 patients (60%), and ≤20 dB in 18/20 patients (90%). There was no significant difference in BC PTA or WRS postoperatively. Two patients (10%) experienced potential transient unmasking of third-window symptoms-hyperacusis and prolonged imbalance-which both resolved. There were no other complications. There was no significant difference in audiologic outcomes or unmasking of third window symptoms between primary or revision cases.

CONCLUSIONS

Persistent conductive hearing loss is common following stapedotomy for otosclerosis in patients with concomitant superior semicircular canal dehiscence. However, a majority of patients can achieve excellent hearing outcomes, while unmasking of third window symptoms appears to be rare. Radiographic superior semicircular canal dehiscence may not be an absolute contraindication to stapes surgery for otosclerosis.

One Genetic Defect and Two Related Entities in Monozygotic Twins: Otosclerosis and Superior Semicircular Canal Near Dehiscence Syndrome

The purpose of this study was to evaluate the clinical and genetic findings of 53-year-old monozygotic twins who had bilateral otosclerosis and right-sided superior semicircular canal near dehiscence (SSCND). Monozygotic twins at the age of 53 presented with conductive hearing loss and normal tympanic membranes. Detailed audiovestibular testing and computed tomography scan revealed that both patients had concurrent otosclerosis and SSCND. Conservative management (hearing aids) was the treatment for these patients. Exome sequencing (ES) for the twins and their affected mother identified a heterozygous missense variant in the EYA4 (c.1744G>A; p.Glu582Lys) gene. This is the first case report to present these separate entities identified in monozygotic twins with a heterozygous missense variant in the EYA4 gene. Our ES data may imply a possible causal relationship or association between variants in the EYA4 gene and concurrent otosclerosis and SSCND.

Decision Making in Patients With Concomitant Otosclerosis and Superior Semicircular Canal Dehiscence: A Systematic Review of the Literature

OBJECTIVE

Concomitant otosclerosis (OTS) and superior semicircular canal dehiscence (SSCD) is a rare, but difficult-to-identify and treat diagnosis. A systematic review of the literature was performed to analyze the diagnostic and therapeutic approaches of concurrent OTS and SSCD cases and to identify possible factors that may help in predicting the surgical outcome.

DATA SOURCES

PubMed, Scopus, Medscape, Ovid databases.

STUDY SELECTION

Studies showing diagnosis of OTS documented by audiometric test with or without associated radiological signs (computed tomography), and concomitant diagnosis of SSCD, documented at least by high-resolution computed tomography (and possibly supported by neurophysiological testing) were included. Both surgically treated and untreated patients were considered for data analysis.

DATA EXTRACTION

The general characteristics of each study were recorded, when available. Clinical, audiological, vestibular testing, surgical, and radiological data were extracted from the published case reports and series, and recorded on a database. For each case, the diagnostic steps that confirmed OTS and concomitant SSCD in the same ear were extracted.

DATA SYNTHESIS

Twelve studies were included in the review and 18 cases affected simultaneously by the 2 conditions were extracted and analyzed. Seven of 12 ears (58.3%) undergoing stapes surgery experienced a hearing improvement. In four (33.3%) cases, vestibular symptoms (with or without associated acoustic symptoms) of SSCD were unmasked or worsened by stapes surgery.

CONCLUSIONS

A reliable preoperative diagnosis of the two concomitant conditions is possible with a proper interpretation of clinical signs, audiometric, and vestibular testing, in association with the radiologic assessment. Despite that the length and the location of the dehiscence may guide the surgical decision, definitive conclusions regarding the appropriate indications for surgical treatment cannot be drawn due to the limited number of cases with adequate data reported in the literature.

A Case Series of Patients With Concurrent Otosclerosis and Superior Semicircular Canal Dehiscence

OBJECTIVE

To describe the presentations and treatment results for patients with concurrent otosclerosis and superior semicircular canal dehiscence (SCD).

STUDY DESIGN

Retrospective case series and literature review.

SETTING

Tertiary academic medical center.

PATIENTS

Patients with concurrent diagnoses of otosclerosis (radiographically and/or surgically confirmed) and SCD (radiographically confirmed) in the same ear.

INTERVENTION(S)

Review of medical records.

MAIN OUTCOME MEASURE(S)

Clinical presentations, outcomes following stapedotomy.

RESULTS

Eight patients with 10 affected ears were identified. All patients presented with slowly progressive conductive hearing loss, normal otoscopy, absent acoustic reflexes, and without other symptoms of SCD syndrome. Seven patients were treated with stapedotomy and 1 with hearing aids. Of those treated with stapedotomy, a persistent conductive hearing loss was the most common hearing result. One patient had near-complete closure of their air bone gap. None had a profound sensorineural hearing loss. Four patients had unmasking of SCD symptoms.

CONCLUSIONS

The clinical and audiometric presentations of patients with concurrent otosclerosis and SCD are often indistinguishable from those of patients with only otosclerosis. Computed tomography of the temporal bone is the only way to identify concurrent SCD. Stapedotomy in these patients typically results in a persistent conductive hearing loss, though 14 to 33% of patients experience near-complete closure of their air bone gap. SCD symptoms are unmasked in 57 to 63% of patients who undergo stapedotomy. Further work is needed to delineate the utility of routine preoperative computed tomography scan in otosclerosis patients, and to identify prognostic factors for patients with concurrent otosclerosis and SCD who wish to undergo stapedotomy.

Current Trends, Controversies, and Future Directions in the Evaluation and Management of Superior Canal Dehiscence Syndrome

Patients with superior canal dehiscence syndrome (SCDS) can present with a range of auditory and/or vestibular signs and symptoms that are associated with a bony defect of the superior semicircular canal (SSC). Over the past two decades, advances in diagnostic techniques have raised the awareness of SCDS and treatment approaches have been refined to improve patient outcomes. However, a number of challenges remain. First, there is currently no standardized clinical testing algorithm for quantifying the effects of superior canal dehiscence (SCD). SCDS mimics a number of common otologic disorders and established metrics such as supranormal bone conduction thresholds and vestibular evoked myogenic potential (VEMP) measurements; although useful in certain cases, have diagnostic limitations. Second, while high-resolution computed tomography (CT) is the gold standard for the detection of SCD, a bony defect does not always result in signs and symptoms. Third, even when SCD repair is indicated, there is a lack of consensus about nomenclature to describe the SCD, ideal surgical approach, specific repair techniques, and type of materials used. Finally, there is no established algorithm in evaluation of SCDS patients who fail primary repair and may be candidates for revision surgery. Herein, we will discuss both contemporary and emerging diagnostic approaches for patients with SCDS and highlight challenges and controversies in the management of this unique patient cohort.

Stapes Surgery Outcomes in Patients With Concurrent Otosclerosis and Superior Semicircular Canal Dehiscence

OBJECTIVE

To review outcomes of stapes surgery in patients with concurrent otosclerosis and superior semicircular canal dehiscence.

STUDY DESIGN

Retrospective case series.

SETTING

Tertiary referral center.

PATIENTS

Patients with concurrent otosclerosis and superior canal dehiscence, confirmed by computed tomography (CT) imaging.

INTERVENTION(S)

Stapes surgery for conductive hearing loss.

MAIN OUTCOME MEASURE(S)

Postoperative air-bone gap (ABG), as well as the number of patients in whom surgery was deemed successful (postoperative ABG <10 dB HL).

RESULTS

Five patients with superior canal dehiscence and concomitant otosclerosis who underwent surgical repair were identified. Mean preoperative ABG was 29.0 ± 6.4 dB HL. Mean postoperative ABG was 13.0 ± 13 dB HL. Three patients (60%) had a successful outcome, defined as postoperative ABG less than 10. One patient experienced unmasking of superior canal dehiscence vestibular symptoms.

CONCLUSIONS

Patients with concurrent otosclerosis and superior canal dehiscence appear to have a lower likelihood of successful hearing restoration following stapes surgery. Patients should be counseled accordingly. Routine preoperative CT imaging before stapes surgery may be helpful to identify patients at risk for poor outcomes.

Failure to close the gap: Concomitant superior canal dehiscence in otosclerosis patients

OBJECTIVE

Superior semicircular canal dehiscence (SSCD) causing conductive hearing loss with present reflexes is a known reason for stapes surgery failure. However, concomitant SSCD and otosclerosis occur rarely. We present a case series of SSCD diagnosed in positively identified otosclerosis patients.

METHODS

Retrospective review of clinical case series in two tertiary-referral neurotologic practices was performed. Clinical histories, operative findings, audiograms, and computed tomography (CT) images were reviewed for patients diagnosed with both SSCD and otosclerosis. Patients with present stapedial reflexes were excluded. Comprehensive literature review was performed.

RESULTS

Four cases were identified. Three reported improved hearing with partial or complete closure of the air-bone gap (ABG), including one patient with far-advanced otosclerosis. One patient had no improvement in pure tone average or ABG. One patient reported worsening of preoperative autophony and pulsatile tinnitus, but none developed new postoperative third-window symptoms. CTs demonstrated both SSCD and otosclerosis.

CONCLUSION

Failure to close the ABG in patients with positively identified otosclerosis intraoperatively may be due to SSCD as an occult concomitant diagnosis. SSCD should be considered as a possible cause of persistent conductive hearing loss after stapes surgery.

LEVEL OF EVIDENCE

4 Laryngoscope, 130:1023-1027, 2020.

Superior semicircular canal dehiscence with concomitant otosclerosis-A literature review and case discussion

Computed tomography scan should be performed as a routine before every stapes surgery, in order to exclude concomitant superior semicircular canal dehiscence, since no other clinical, audiological, or electro-physiological criteria are available to exclude concomitant superior semicircular canal dehiscence in the otosclerotic temporal bone.

Diagnosis of Superior Semicircular Canal Dehiscence in the Presence of Concomitant Otosclerosis

OBJECTIVE

To review three patients with concurrent otosclerosis and superior canal dehiscence identified before operative intervention and provide a practical diagnostic approach to this clinical scenario.

STUDY DESIGN

Retrospective patient series.

SETTING

Tertiary/quaternary referral center.

PATIENTS

Individuals with confirmed diagnoses of concurrent otosclerosis and superior semicircular canal dehiscence syndrome.

INTERVENTIONS

Detailed history and physical examinations were performed on these patients, as well as detailed audiovestibular testing and computed tomography imaging.

MAIN OUTCOME MEASURES

Establishing a clear diagnosis of concurrent otosclerosis and superior semicircular canal dehiscence syndrome using a thorough diagnostic approach.

RESULTS

Three patients presented with conductive hearing loss and normal tympanic membranes. When history and physical examination yielded suspicious third window symptoms/signs, more detailed audiovestibular testing and computed tomography scan imaging were performed. All three patients were ultimately identified to have concurrent otosclerosis and superior canal dehiscence. Conservative management was the option of choice for two of these patients (trial of a hearing aid) and surgical intervention was performed to treat the otosclerosis in the remaining patient.

Superior Canal Dehiscence Syndrome: Lessons from the First 20 Years

Superior semicircular canal dehiscence syndrome was first reported by Lloyd Minor and colleagues in 1998. Patients with a dehiscence in the bone overlying the superior semicircular canal experience symptoms of pressure or sound-induced vertigo, bone conduction hyperacusis, and pulsatile tinnitus. The initial series of patients were diagnosed based on common symptoms, a physical examination finding of eye movements in the plane of the superior semicircular canal when ear canal pressure or loud tones were applied to the ear, and high-resolution computed tomography imaging demonstrating a dehiscence in the bone over the superior semicircular canal. Research productivity directed at understanding better methods for diagnosing and treating this condition has substantially increased over the last two decades. We now have a sound understanding of the pathophysiology of third mobile window syndromes, higher resolution imaging protocols, and several sensitive and specific diagnostic tests. Furthermore, we have a treatment (surgical occlusion of the superior semicircular canal) that has demonstrated efficacy. This review will highlight some of the fundamental insights gained in SCDS, propose diagnostic criteria, and discuss future research directions.

Ocular vestibular evoked myogenic potentials to vertex low frequency vibration as a diagnostic test for superior canal dehiscence

OBJECTIVE

To explore ocular vestibular evoked myogenic potentials (oVEMP) to low-frequency vertex vibration (125 Hz) as a diagnostic test for superior canal dehiscence (SCD) syndrome.

METHODS

The oVEMP using 125 Hz single cycle bone-conducted vertex vibration were tested in 15 patients with unilateral superior canal dehiscence (SCD) syndrome, 15 healthy controls and in 20 patients with unilateral vestibular loss due to vestibular neuritis. Amplitude, amplitude asymmetry ratio, latency and interaural latency difference were parameters of interest.

RESULTS

The oVEMP amplitude was significantly larger in SCD patients when affected sides (53 μVolts) were compared to non-affected (17.2 μVolts) or compared to healthy controls (13.6 μVolts). Amplitude larger than 33.8 μVolts separates effectively the SCD ears from the healthy ones with sensitivity of 87% and specificity of 93%. The other three parameters showed an overlap between affected SCD ears and non-affected as well as between SCD ears and those in the two control groups.

CONCLUSIONS

oVEMP amplitude distinguishes SCD ears from healthy ones using low-frequency vibration stimuli at vertex.

SIGNIFICANCE

Amplitude analysis of oVEMP evoked by low-frequency vertex bone vibration stimulation is an additional indicator of SCD syndrome and might serve for diagnosing SCD patients with coexistent conductive middle ear problems.

Acoustic Reflex Screening of Conductive Hearing Loss for Third Window Disorders

Objective

This study examines the effectiveness of acoustic reflexes in screening for third window disorders (eg, superior semicircular canal dehiscence) prior to middle ear exploration for conductive hearing loss.

Study Design

Case series with chart review.

Setting

Outpatient tertiary otology center.

Subjects and Methods

A review was performed of 212 ears with acoustic reflexes, performed as part of the evaluation of conductive hearing loss in patients without evidence of chronic otitis media. The etiology of hearing loss was determined from intraoperative findings and computed tomography imaging. The relationship between acoustic reflexes and conductive hearing loss etiology was assessed.

Results

Eighty-eight percent of ears (166 of 189) demonstrating absence of all acoustic reflexes had an ossicular etiology of conductive hearing loss. Fifty-two percent of ears (12 of 23) with at least 1 detectable acoustic reflex had a nonossicular etiology. The positive and negative predictive values for an ossicular etiology were 89% and 57% when acoustic reflexes were used alone for screening, 89% and 39% when third window symptoms were used alone, and 94% and 71% when reflexes and symptoms were used together, respectively.

Conclusion

Acoustic reflex testing is an effective means of screening for third window disorders in patients with a conductive hearing loss. Questioning for third window symptoms should complement screening. The detection of even 1 acoustic reflex or third window symptom (regardless of reflex status) should prompt further workup prior to middle ear exploration.

Surgical treatment of hearing loss when otosclerosis coexists with superior semicircular canal dehiscence syndrome

OBJECTIVE

Document a case of bilateral otosclerosis with coexisting bilateral superior semicircular canal dehiscence syndrome and the treatment of hearing loss in this setting.

PATIENT

A 33-year-old woman presented with bilateral mixed hearing loss; worse in the left ear. This was gradual in onset, and she denied dizziness. Computerized tomographic scan revealed fenestral otosclerosis and a large dehiscence of the superior semicircular canal bilaterally. She declined amplification.

INTERVENTION

Sequential laser-assisted stapedotomy with insertion of a Kurz titanium CliP Piston prosthesis.

MAIN OUTCOME MEASURE

Comparison of audiovestibular symptoms, hearing thresholds, and neurodiagnostic testing results preoperatively and postoperatively.

RESULTS

Hearing improved bilaterally with closure of the air-bone gaps at most frequencies, and she has not had permanent vestibular symptoms. Postoperative follow-up time is 37 months for the left ear and 13 months for the right ear.

CONCLUSION

When otosclerosis and superior semicircular canal dehiscence syndrome coexist and hearing loss is the dominant symptom, stapes surgery can be effective for improving hearing without permanent vestibular symptoms.

Surgical and clinical confirmation of temporal bone CT findings in patients with otosclerosis with failed stapes surgery

BACKGROUND AND PURPOSE

Prior descriptions of imaging after failed stapes procedures for otosclerosis predated currently available CT technology and/or failed to assess commonly used metallic implants. The purpose of this study was to correlate temporal bone CT findings with clinically and intraoperatively determined causes of surgical failure.

MATERIALS AND METHODS

All patients with otosclerosis undergoing stapedectomy between December 1999 and December 2010 were identified from a search of neurotology clinical records. Patients presenting because of failed stapes surgery and having temporal bone CT scans at the time of revision surgery or clinical evaluation were included. Imaging and clinical records were retrospectively evaluated by a medical student, radiology resident, and senior neuroradiologist. Stapes prosthesis complications and relevant anatomic CT findings were correlated to clinical and intraoperative findings.

RESULTS

Twenty-two of 340 patients met inclusion criteria. Temporal bone CT findings were correlated to intraoperative findings in 17 of 22 patients and to clinical findings in 5 of 22 patients. Surgically confirmed abnormalities included 7 of 7 incus erosions, 3 of 6 piston re-sizings, 3 of 5 granulation tissues, 3 of 5 prosthesis disconnections, 3 of 4 obliterative otosclerosis, 2 of 2 oval window dislocations, and 1 labyrinthine ossificans. Clinically confirmed abnormalities included 2 cases each of superior semicircular canal dehiscence, and wrong piston size, and 1 each of piston disconnection, labyrinthine ossificans, and intravestibular footplate.

CONCLUSIONS

CT evaluation in the setting of failed stapes surgery is challenging. Many postoperative complications such as piston migration, incus necrosis, and overt vestibular penetration are well recognized on temporal bone CT. Of particular note, superior semicircular canal dehiscence is an important contraindication to stapes surgery.

Surgery of the ear and the lateral skull base: pitfalls and complications

Surgery of the ear and the lateral skull base is a fascinating, yet challenging field in otorhinolaryngology. A thorough knowledge of the associated complications and pitfalls is indispensable for the surgeon, not only to provide the best possible care to his patients, but also to further improve his surgical skills. Following a summary about general aspects in pre-, intra-and postoperative care of patients with disorders of the ear/lateral skull base, this article covers the most common pitfalls and complications in stapes surgery, cochlear implantation and surgery of vestibular schwannomas and jugulotympanal paragangliomas. Based on these exemplary procedures, basic "dos and don'ts" of skull base surgery are explained, which the reader can easily transfer to other disorders. Special emphasis is laid on functional aspects, such as hearing, balance and facial nerve function. Furthermore, the topics of infection, bleeding, skull base defects, quality of life and indication for revision surgery are discussed. An open communication about complications and pitfalls in ear/lateral skull base surgery among surgeons is a prerequisite for the further advancement of this fascinating field in ENT surgery. This article is meant to be a contribution to this process.

Superior canal dehiscence in a patient with three failed stapedectomy operations for otosclerosis: a case report

INTRODUCTION

This case illustrates that superior semicircular canal dehiscence syndrome can be associated with a "pseudo"-conductive hearing loss, a symptom that overlaps with the clinical appearance of otosclerosis.

CASE PRESENTATION

We present the case of a 48-year-old German Caucasian woman presenting with hearing loss on the left side and vertigo. She had undergone three previous stapedectomies for hearing improvement. Reformatted high-resolution computed tomographic scanning and the patient's history confirmed the diagnosis of concurrent canal dehiscence syndrome.

CONCLUSION

Failure of hearing improvement after otosclerosis surgery may indicate an alternative underlying diagnosis which should be explored by further appropriate evaluation.