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

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.

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.

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.

Imaging Studies in Otosclerosis: An Up-to-date Comprehensive Review

Introduction  Otosclerosis is a primary osteodystrophy of the otic capsule, frequently responsible for acquired hearing loss in adults. Although the diagnostic value of imaging investigations in otosclerosis is debatable, they might still be employed with different goals within the context of the disease.

Objectives  The present paper aims to review the most recent literature on the use of imaging studies in otosclerosis for the most varied purposes, from routine application and differential diagnosis to prognostic prediction and investigation of surgical failure.

Data Synthesis  The diagnosis of otosclerosis is usually clinical, but computed tomography (CT) is paramount in particular cases for the differential diagnosis. The routine use, however, is not supported by strong evidence. Even so, there is growing evidence of the role of this method in surgical planning and prediction of postoperative prognosis. In specific scenarios, for example when superior semicircular canal dehiscence (SSCD) syndrome is suspected or in surgical failure, CT is crucial indeed. Magnetic resonance imaging (MRI), however, has limited – although important – indications in the management of individuals with otosclerosis, especially in the evaluation of postoperative complications and in the follow-up of medical treatment in active ostosclerosis.

Conclusion  Imaging studies have a broad range of well-established indications in otosclerosis. Besides, although the routine use of CT remains controversial, the most recent papers have shed light into new potential benefits of imaging prior to surgery.

CT evaluation of normal bone thickness overlying the superior semicircular canal

Superior semicircular canal dehiscence (SSCD) is a rare inner ear disorder with variable amounts of auditory and vestibular dysfunction. In addition to the absence of bone overlying the superior semicircular canal, thinning of bone in this area can also initiate the vestibulocochlear symptoms of SSCD. We evaluated normal bone thickness overlying the course of the semicircular canal using computed tomography (CT) scans and assessed correlations between bone thickness and age, gender, and location of the thinnest bone. A single-institution retrospective chart review was conducted on 133 high-resolution CT scans from 76 healthy, asymptomatic patients between ages 9 and 96 years. These CT scans of the temporal bone were obtained between January 2012 and August 2017. The superior semicircular canal dome thickness at the apex was reported with a mean of 1.25 mm for all 76 patients; the 10th percentile was 0.60 mm, and the 90th percentile was 2.08 mm. The thinnest area of bone at any location yielded a mean of 0.86 mm. The normal bone thickness overlying the superior semicircular canal does not depend on gender or age. The thinnest location was evenly distributed across the superior semicircular canal. A bone thickness of 0.40 mm or greater was present in 90% of normal patients based on CT scan measurements at the thinnest location.