Symptomatic Superior Canal Dehiscence Research Articles

Superior Canal Dehiscence Similarly Affects Cochlear Pressures in Temporal Bones and Audiograms in Patients.

The diagnosis of superior canal dehiscence (SCD) is challenging and audiograms play an important role in raising clinical suspicion of SCD. The typical audiometric finding in SCD is the combination of increased air conduction (AC) thresholds and decreased bone conduction thresholds at low frequencies. However, this pattern is not always apparent in audiograms of patients with SCD, and some have hearing thresholds that are within the normal reference range despite subjective reports of hearing impairment. In this study, we used a human temporal bone model to measure the differential pressure across the cochlear partition (PDiff) before and after introduction of an SCD. PDiff estimates the cochlear input drive and provides a mechanical audiogram of the temporal bone. We measured PDiff across a wider frequency range than in previous studies and investigated whether the changes in PDiff in the temporal bone model and changes of audiometric thresholds in patients with SCD were similar, as both are thought to reflect the same physical phenomenon. We measured PDiff across the cochlear partition in fresh human cadaveric temporal bones before and after creating an SCD. Measurements were made for a wide frequency range (20 Hz to 10 kHz), which extends down to lower frequencies than in previous studies and audiograms. PDiff = PSV- PST is calculated from pressures measured simultaneously at the base of the cochlea in scala vestibuli (PSV) and scala tympani (PST) during sound stimulation. The change in PDiff after an SCD is created quantifies the effect of SCD on hearing. We further included an important experimental control-by patching the SCD, to confirm that PDiff was reversed back to the initial state. To provide a comparison of temporal bone data to clinical data, we analyzed AC audiograms (250 Hz to 8kHz) of patients with symptomatic unilateral SCD (radiographically confirmed). To achieve this, we used the unaffected ear to estimate the baseline hearing function for each patient, and determined the influence of SCD by referencing AC hearing thresholds of the SCD-affected ear with the unaffected contralateral ear. PDiff measured in temporal bones (n = 6) and AC thresholds in patients (n = 53) exhibited a similar pattern of SCD-related change. With decreasing frequency, SCD caused a progressive decrease in PDiff at low frequencies for all temporal bones and a progressive increase in AC thresholds at low frequencies. SCD decreases the cochlear input drive by approximately 6 dB per octave at frequencies below ~1 kHz for both PDiff and AC thresholds. Individual data varied in frequency and magnitude of this SCD effect, where some temporal-bone ears had noticeable effects only below 250 Hz. We found that with decrease in frequency the progressive decrease in low-frequency PDiff in our temporal bone experiments mirrors the progressive elevation in AC hearing thresholds observed in patients. This hypothesis remains to be tested in the clinical setting, but our findings suggest that that measuring AC thresholds at frequencies below 250 Hz would detect a larger change, thus improving audiograms as a diagnostic tool for SCD.

Superior Canal Dehiscence Surgery Outcomes Following Failed Round Window Surgery.

Round window (RW) occlusion or reinforcement is a less-invasive option compared with direct repair approaches to improve symptoms of superior canal dehiscence (SCD) syndrome. However, RW surgery is associated with variable outcomes. Middle fossa craniotomy or transmastoid repair is an option for SCD patients who fail RW surgery, but it is unknown whether sequential repair following RW plugging improves SCD symptoms or increases complications. The objective of this study is to evaluate outcomes of SCD repair via middle fossa craniotomy following failed RW surgery. Retrospective review. Academic tertiary care center. Adult patients with SCD syndrome who underwent failed RW surgery followed by sequential middle fossa craniotomy and plugging of the arcuate eminence defect. Patients with SCD associated with the superior petrosal sinus were excluded. None. Prospectively collected pre- and postoperative symptom questionnaires, threshold audiograms, and cervical vestibular evoked myogenic potentials (cVEMP). Seven SCD patients (out of a total of 194 surgical cases at our institution) underwent sequential middle-fossa SCD repair following failed RW surgery. Resolution of symptoms and reversal of diagnostic indicators were observed in the majority of subjects following sequential repair. Two of seven patients underwent a third procedure with plugging of the superior semicircular canal by a transmastoid approach due to the presence of residual symptoms. Middle fossa craniotomy and SCD occlusion is a safe and reasonable option for patients who fail RW surgery. Our cohort did not show increased risks of auditory or vestibular dysfunction.

Audiometric and cVEMP Thresholds Show Little Correlation With Symptoms in Superior Semicircular Canal Dehiscence Syndrome.

Evaluate the relationship between objective audiometric and vestibular tests and patient symptoms in superior canal dehiscence (SCD) syndrome. Retrospective chart review. Tertiary care center. Ninety-eight patients with SCD, preoperative threshold audiograms, cervical vestibular evoked myogenic potential (cVEMP) thresholds, and computed tomography (CT) imaging were included. Clinical reports were reviewed for self-reported SCD symptoms. Twenty-five patients completed the Hearing Handicap Inventory (HHI), Dizziness Handicap Inventory (DHI), Autophony Index (AI), and the 36-item Short Form Survey (SF-36). Correlations between preoperative low-frequency air-bone gap (ABG), cVEMP thresholds, and symptoms (including HHI, DHI, AI, and SF-36). Symptoms included hearing loss, aural fullness, autophony, hyperacusis, tinnitus, vertigo, imbalance and sound-, pressure and exercise provoked dizziness. Secondary outcome measure: Correlations between changes of objective and subjective measures before and after surgery. Patients who reported hearing loss had larger ABGs at 250 Hz than patients without subjective hearing loss (p = 0.001). ABGs and cVEMP thresholds did not correlate with any other symptom. No significant correlation was found between ABG or cVEMP threshold and the HHI, DHI, AI or Health Utility Value (derived from the SF-36 quality of life score). Following SCD surgery, ABG decreased (p < 0.001), cVEMP thresholds increased (p < 0.001) and overall symptoms, handicap scores and quality-of-life improved; however, there was no significant relationship between these measures. While threshold audiometry and cVEMP are important tools to diagnose SCD and monitor surgical outcomes, these measures showed no significant correlation with vestibular and most auditory symptoms or their severity.

Toward Optimizing Cervical Vestibular Evoked Myogenic Potentials (cVEMP): Combining Air-Bone Gap and cVEMP Thresholds to Improve Diagnosis of Superior Canal Dehiscence.

To develop a novel approach combining low-frequency air-bone gap (ABG) and cervical vestibular evoked myogenic potential (cVEMP) thresholds to improve screening for superior canal dehiscence (SCD) syndrome. Retrospective study. Tertiary care center. One hundred forty patients with SCD and 21 healthy age-matched controls were included. Ears for each patient were divided into three groups based on computed tomography (CT) findings: 1) dehiscent, 2) thin, or 3) unaffected. cVEMP and audiometric thresholds were analyzed and differences among groups were evaluated. We define the third window indicator (TWI) as the cVEMP thresholds at 500, 750, and 1000 Hz adjusted for the ABG at 250 Hz (i.e., subtracting ABG from cVEMP threshold). The TWI differentiates between dehiscent and nondehiscent control ears with a sensitivity of 82% and specificity of 100%, corresponding to a positive predictive value of 100%. ABGs and cVEMP thresholds were similar for healthy controls and patients with thin bone over the superior canal. This is the largest study to date examining the usefulness of cVEMPs in the diagnosis of SCD. Our "third window indicator" (TWI) combines cVEMP thresholds with the ABG at 250 Hz to improve the ability to screen patients with SCD symptoms.

Relationship between Surgically Treated Superior Canal Dehiscence Syndrome and Body Mass Index.

Objective Examine the association between body mass index (BMI) and superior canal dehiscence (SCD) among patients who have undergone surgical repair for superior canal dehiscence. Study Design Retrospective comparison study. Setting Neurotology tertiary care center. Subjects and Methods Retrospective review of consecutive adult patients evaluated at our institution for SCD syndrome between November 2006 and August 2015. A control group who underwent imaging within the same period for reasons other than SCD was also included. Patient demographics, weight, and height were examined. We performed multiple subgroup analyses to investigate the relationship of BMI, surgery vs no surgery, and correlation between patient BMI and SCD size. Results Of the 268 patients with SCD, 99 underwent surgery; 96 of these patients had complete medical records and were eligible for inclusion. Eighty-eight patients were noted to have arcuate eminence defects, and the mean BMI of this surgical cohort was 28.09 ± 5.26 kg/m2. Nonsurgically treated patients with SCD with available data (n = 94) had a mean BMI of 27.97 ± 6.95 kg/m2. A control group of 204 patients who underwent computed tomography for non-SCD-related causes was analyzed, of whom 155 had available data with a mean BMI of 27.91 ± 6.38 kg/m2. Conclusion We demonstrate that adult patients who undergo surgery for SCD are not obese (mean BMI <30), and size of dehiscence poorly correlates with BMI. Our observations call into question the proposed theory that patient weight is a risk factor for the development of symptomatic SCD involving the arcuate eminence.

Audiologic, cVEMP, and Radiologic Progression in Superior Canal Dehiscence Syndrome.

To assess the change in hearing, vestibular function, and size of superior canal dehiscence (SCD) in patients with SCD syndrome over time. Adult patients with SCD in one or both ears with documented sign and symptom progression, as shown by the medical record, audiometry, cervical vestibular-evoked myogenic potentials (cVEMP), and computed tomography (CT). Audiometry, cVEMPs, and temporal bone CT were performed on patients with high clinical suspicion of disease progression. Audiometry (magnitude of the air-bone gap [ABG]), cVEMP (magnitude of the thresholds), and CT scans (size of the superior canal dehiscence) were analyzed. Symptoms were assessed at each clinical visit and before repeat testing. Retrospective review of 250 patients with SCDS showed three patients with disease progression over time with follow-up testing as outlined above. All patients presented initially with mild symptoms, ABGs, low cVEMP thresholds, and small bony defects of the arcuate eminence. Four, 6, and 8 years later, progression of SCD signs and symptoms was observed in these three patients, respectively. Audiometry showed larger ABGs and lower cVEMP thresholds compared with previous testing. CT showed an increase in bony defect size. Progression of SCD symptoms can be associated with a wider air-bone gap, lower cVEMP thresholds, and a larger bony defect. Prospective studies using validated measures of hearing loss and dizziness in patients who have not yet undergone surgery for SCD will determine the association between specific symptoms and objective test outcomes and how these change over time.

Three-Dimensional Printed Prosthesis for Repair of Superior Canal Dehiscence.

Outcomes following repair of superior canal dehiscence (SCD) are variable, and surgery carries a risk of persistent or recurrent SCD symptoms, as well as a risk of hearing loss and vestibulopathy. Poor outcomes may occur from inadequate repair of the SCD or mechanical insult to the membranous labyrinth. Repair of SCD using a customized, fixed-length prosthesis may address current operative limitations and improve surgical outcomes. We aim to 3-dimensionally print customized prostheses to resurface or occlude bony SCD defects. Dehiscences were created along the arcuate eminence of superior semicircular canals in cadaveric temporal bones. Prostheses were designed and created using computed tomography and a 3-dimensional printer. The prostheses occupied the superior semicircular canal defect, reflected in postrepair computed tomography scans. This novel approach to SCD repair could have advantages over current techniques. Refinement of prosthesis design and materials will be important if this approach is translated into clinical use.

Electrocochleographic findings in superior canal dehiscence syndrome

This study evaluated the electrocochleographic findings of patients with superior canal dehiscence (SCD) syndrome and determined their diagnostic values and relationships with audiometric parameters. Thirteen symptomatic SCD patients (1 bilateral) confirmed by temporal bone computed tomography (TBCT) and cervical vestibular evoked myogenic potentials (cVEMP) were recruited. SCD sizes were measured on reformatted images in the plane of the superior canal (SC). Results of audiologic tests (audiometry, cVEMP, electrocochleography (ECoG)) for 14 affected and 12 contralateral unaffected ears were evaluated. Relationships between summating potential (SP) to action potential (AP) ratios, as measured by ECoG, and other audiometric parameters were evaluated. Sensitivity analysis of SP/AP ratios was performed by plotting receiver operating characteristic (ROC) curves for SCD syndrome patients and 19 age-matched healthy controls. Mean SP/AP ratio of SCD ears was significantly higher than that of unaffected ears (0.52 versus 0.25, p < 0.001) and SPs were significantly elevated in affected ears (p = 0.011), whereas APs were similar for affected and unaffected ears. SP/AP ratio showed a sensitivity of 92.3% and a specificity of 94.0% for distinguishing SCD syndrome patients given the inclusion criteria applied (symptoms, TBCT, cVEMP threshold) at a cutoff value of 0.34 (p < 0.001). SP/AP ratio was not correlated with SCD size or cVEMP threshold in affected ears. Negative absolute values of bone conduction at low frequency tended to increase with SP/AP ratio. Five out of 13 patients underwent surgical repair experienced symptomatic improvement with normalization of SP/AP ratios. ECoG appears to be a valuable diagnostic adjunct for functional demonstration of the third window in the otic capsule with high sensitivity and specificity, and thus, can support a clinical diagnosis of SCD when used in conjunction with clinical and radiological findings.

Familial Superior Canal Dehiscence Syndrome

The etiology of superior canal dehiscence (SCD) involving the arcuate eminence is not completely understood, but genetic factors may play a role. One hypothesis is that patients are born with a defect of the superior canal, and an acute event (such as head trauma) or progressive loss of bone (eg, due to dural pulsations) may result in the onset of SCD symptoms. Familial SCD has only been briefly mentioned in the literature to date. We report 3 families that each had 2 members with SCD syndrome. We found that first-degree relatives presented with similar complaints and that temporal bone computed tomography scans between relatives showed very similar skull base topography and anatomic SCD defects. The presence of symptomatic SCD among first-degree relatives and similar skull base topography suggests that genetics may play a role in the etiology of SCD.

Costimulation of the Horizontal Semicircular Canal during Skull Vibrations in Superior Canal Dehiscence Syndrome

A sound- and pressure-induced vestibuloocular reflex (VOR) has been described as vertical and torsional in superior canal dehiscence (SCD), and the rotational axes of induced VOR have been assumed to fit with the axis of the affected superior semicircular canal (SC). However, it has been difficult to characterize the pattern of vibration-induced VOR (ViVOR). We aimed to characterize the pattern of ViVOR by comparing the intensity and the axis of ViVOR with several clinical parameters of SCD. Ten symptomatic SCD patients were recruited. SCD size and location were measured on a reformatted image in the plane of the SC. Unilateral vibratory stimulation (100 Hz) was applied to the mastoid surface. ViVOR were recorded using 3D videooculography. The median 3D velocity of ViVOR was measured and the 3D vector trajectory plotted for reference against the axes of the human semicircular canals. A correlation between the magnitude of ViVOR and the size of SCD was evaluated. We also compared the location of SCD with the vertical-to-torsional component ratio of the ViVOR. ViVOR were present in 7 patients; 6 patients showed a substantial horizontal component in the excitatory direction in addition to strong torsional and weak vertical components. The computed rotational axes of ViVOR were located mostly between the axes of the ipsilateral SC and horizontal canal (HC) with a variable deviation to the axis of the ipsilateral posterior canal (PC). The magnitude of ViVOR was not related to the size of the SCD. The vertical-to-torsional component ratio of ViVOR tended to decline as the dehiscence was closer to the common crus. In SCD, mastoid vibration may stimulate the affected-side HC and PC as well as the SC. SCD can be suspected when excitatory horizontal torsional ViVOR direct to the side of the auditory symptoms.

Superior Canal Dehiscence

Identify independent clinical and audiometric factors to predict a positive high-resolution computed tomography (HRCT) scan for superior canal dehiscence (SCD). Retrospective chart review. Tertiary referral center. Patients presenting SCD. Audiogram, VEMP, temporal bone HRCT, and SCD symptoms and signs chart. ABG, VEMP threshold, and symptoms and signs. Approximately 106 patients with SCD symptoms were included: 62 had a positive and 44 had a negative CT scan. The positive scan group showed a higher average of cochlear symptoms than the negative CT scan group (4.3 versus 2.6) (p < 0.001), but no statistical difference for vestibular symptoms (2.2 versus 1.8) was identified. CVEMP thresholds of the positive and negative CT scan groups were of 66 and 81 dB, respectively (p < 0.001). The positive CT scan group showed higher ABGs at 250 Hz (24 versus 14 dB) and 500 Hz (17 versus 8 dB) (p = 0.008 and p = 0.008, resectively). No statistical significance was found when comparing both groups for air and bone conduction thresholds. Approximately 23% of the positive CT scan group showed a Valsalva-induced vertigo against 2.3% of the negative scan group (p = 0.003); 27% of the positive CT scan group showed speculum-induced vertigo but none of the negative scan patients (p < 0.001). Using logistic regression, we found that each 10-dB unit increase in the 250 Hz ABG is associated to an increase odd of having SCD of 51% (OR, 1.51; 95% CI, 1.10-2.08). Nature and number of cochlear symptoms, Valsalva and pneumatic speculum-induced vertigo, VEMP thresholds, and ABGs seem to correlate with a positive HRCT. The ABG at 250 Hz is the most accurate predictor of SCD.

Dizziness Handicap After Cartilage Cap Occlusion for Superior Semicircular Canal Dehiscence

To evaluate the change in self-reported dizziness handicap after surgical repair using the cartilage cap occlusion technique in cases of superior canal dehiscence (SCD). Repeated measures, retrospective chart review. Tertiary referral center. Twenty patients over a 2-year period who underwent surgical repair of SCD using the cartilage cap occlusion technique. Therapeutic. Preoperative and postoperative Dizziness Handicap Inventory (DHI) questionnaires were completed (median, interquartile range). Preoperative (48, 28-56) and postoperative (33, 19-50) total scores were not significantly different. Scores for patients with moderate/severe preoperative DHI scores (DHI, >30; n = 14) demonstrated significant change (p = 0.001, Wilcoxon paired sample test), whereas those with mild scores did not (DHI, ≤ 30; n = 6; p = 0.67). Change in DHI score is variable. As described by DHI score, patients with higher preoperative handicap may demonstrate significant improvement after surgery, whereas those with mild handicap may not. These results are similar to previous reports and indicate that the cartilage cap occlusion technique may provide an alternative to middle fossa craniotomy approach for surgical management of symptomatic SCD.

Round Window Reinforcement for Superior Canal Dehiscence

Objective: To evaluate the outcome of round window (RW) with or without oval window (OW) tissue reinforcement in the management of superior canal dehiscence (SCD). Method: Chart reviews were perfomed for patients with symptomatic SCD that underwent this window reinforcement procedure. Preoperative and postoperative audiometry, vestibular myogenic evoked potentials (VEMP), and presence of a positive Tullio and Hennebert’s sign were recorded. Patient questionnaires were administered to assess symptomatic relief following the procedure. Results: Twenty-five chart reviews from 5 tertiary centers revealed that most patients experienced reduction of symptoms and were satisfied with the results. A comprehensive analysis will be presented. Conclusion: Tissue reinforcement of the windows(s) may reduce some of the symptoms associated with SCD, perhaps by mitigating some of the presumed “third window” effect of the dehiscence. Most patients were grateful for the benefits provided by the procedure and the avoidance of a craniotomy or mastoidectomy.

Second-Side Surgery in Superior Canal Dehiscence Syndrome

Bilateral superior canal (SC) dehiscence syndrome poses a challenge because bilateral SC dehiscence (SCD) plugging might be expected to result in oscillopsia and disability. Our aims were as follows: 1) to evaluate which symptoms prompted patients with bilateral SCD syndrome (SCDS) to seek second-side surgery, and 2) to determine the prevalence of disabling imbalance and oscillopsia after bilateral SC plugging. Prospective observational study. Tertiary referral center. Five patients with bilateral SCDS based on history, audiometric and physiologic testing, and computed tomographic findings. This includes all of our patients who have had second-side plugging surgery to date. Bilateral sequential middle fossa craniotomy and plugging of SCs. Cochleovestibular symptoms, cervical and ocular vestibular-evoked myogenic potential testing, dizziness handicap inventory, short-form 36 Health Survey, dynamic visual acuity testing. The most common symptoms prompting second-side surgery were sound- and pressure-induced vertigo and autophony. Three of the 5 patients reported that symptoms shifted to the contralateral ear immediately after plugging the first side, whereas in 2 patients, contralateral symptoms developed several years after the first SC plugging. Two of 4 patients experienced ongoing oscillopsia after bilateral SCDS surgery; however, all patients reported relief from their SCD symptoms and were glad that they had pursued bilateral surgery. In patients with bilateral SCDS, sound- and pressure-induced vertigo most commonly prompted second-side surgery. Despite some degree of oscillopsia after bilateral SCDS surgery, patients were very satisfied with second-side surgery, given their relief from other SCDS symptoms.

Clinical experience with symptomatic superior canal dehiscence in a single neurotologic practice

To discuss the range of signs and symptoms of patients with superior canal dehiscence syndrome identified in a single neurotologic practice. Retrospective chart review of 35 patients diagnosed with superior canal dehiscence from April 2000 to June 2007. All patients had evidence of superior canal dehiscence on computed tomography. These 35 patients represented 0.56% of new patients seen over a five-year period. The incidence of clinical symptoms and signs is compared to other published series. The mean vestibular evoked myogenic potential thresholds of affected ears are significantly lower than the mean vestibular evoked myogenic potential thresholds of unaffected ears. To date, 5 of 35 patients have undergone transmastoid occlusion of the superior semicircular canal with significant improvement in clinical symptoms in 4 of 5 cases. Not all patients with a diagnosis of superior canal dehiscence syndrome will have classic symptoms and signs. A high index of suspicion with careful clinical examination and properly performed ancillary testing is required to confirm this diagnosis.