Assessment of the effects of superior canal dehiscence location and size on intracochlear sound pressures.

Superior canal dehiscence (SCD) is a defect in the bony covering of the superior semicircular canal. Patients with SCD present with a wide range of symptoms, including hearing loss, yet it is unknown whether hearing is affected by parameters such as the location of the SCD. Our previous human cadaveric temporal bone study, utilizing intracochlear pressure measurements, generally showed that an increase in dehiscence size caused a low-frequency monotonic decrease in the cochlear drive across the partition, consistent with increased hearing loss. This previous study was limited to SCD sizes including and smaller than 2 mm long and 0.7 mm wide. However, the effects of larger SCDs (>2 mm long) were not studied, although larger SCDs are seen in many patients. Therefore, to answer the effect of parameters that have not been studied, this present study assessed the effect of SCD location and the effect of large-sized SCDs (>2 mm long) on intracochlear pressures. We used simultaneous measurements of sound pressures in the scala vestibuli and scala tympani at the base of the cochlea to determine the sound pressure difference across the cochlear partition - a measure of the cochlear drive in a temporal bone preparation - allowing for assessment of hearing loss. We measured the cochlear drive before and after SCDs were made at different locations (e.g. closer to the ampulla of the superior semicircular canal or closer to the common crus) and for different dehiscence sizes (including larger than 2 mm long and 0.7 mm wide). Our measurements suggest the following: (1) different SCD locations result in similar cochlear drive and (2) larger SCDs produce larger decreases in cochlear drive at low frequencies. However, the effect of SCD size seems to saturate as the size increases above 2-3 mm long and 0.7 mm wide. Although the monotonic effect was generally consistent across ears, the quantitative amount of change in cochlear drive due to dehiscence size varied across ears. Additionally, the size of the dehiscence above which the effect on hearing saturated varied across ears. These findings show that the location of the SCD does not generally influence the amount of hearing loss and that SCD size can help explain some of the variability of hearing loss in patients.

Superior canal dehiscence length and location influences clinical presentation and audiometric and cervical vestibular-evoked myogenic potential testing.

Superior canal dehiscence (SCD) is caused by an absence of bony covering of the arcuate eminence or posteromedial aspect of the superior semicircular canal. However, the clinical presentation of SCD syndrome varies considerably, as some SCD patients are asymptomatic and others have auditory and/or vestibular complaints. In order to determine the basis for these observations, we examined the association between SCD length and location with: (1) auditory and vestibular signs and symptoms; (2) air conduction (AC) loss and air-bone gap (ABG) measured by pure-tone audiometric testing, and (3) cervical vestibular-evoked myogenic potential (cVEMP) thresholds. 104 patients (147 ears) underwent SCD length and location measurements using a novel method of measuring bone density along 0.2-mm radial CT sections. We found that patients with auditory symptoms have a larger dehiscence (median length: 4.5 vs. 2.7 mm) with a beginning closer to the ampulla (median location: 4.8 vs. 6.4 mm from ampulla) than patients with no auditory symptoms (only vestibular symptoms). An increase in AC threshold was found as the SCD length increased at 250 Hz (95% CI: 1.7-4.7), 500 Hz (95% CI: 0.7-3.5) and 1,000 Hz (95% CI: 0.0-2.5), and an increase in ABG as the SCD length increased at 250 Hz (95% CI: 2.0-5.3), 500 Hz (95% CI: 1.6-4.6) and 1,000 Hz (95% CI: 1.3-3.3) was also seen. Finally, a larger dehiscence was associated with lowered cVEMP thresholds at 250 Hz (95% CI: -4.4 to -0.3), 500 Hz (95% CI: -4.1 to -1.0), 750 Hz (95% CI: -4.2 to -0.7) and 1,000 Hz (95% CI: -3.6 to -0.5) and a starting location closer to the ampulla at 250 Hz (95% CI: 1.3-5.1), 750 Hz (95% CI: 0.2-3.3) and 1,000 Hz (95% CI: 0.6-3.5). These findings may help to explain the variation of signs and symptoms seen in patients with SCD syndrome.

Bilateral low-frequency repetitive transcranial magnetic stimulation of the auditory cortex in tinnitus patients is not effective: a randomised controlled trial.

BACKGROUND: Although some therapies may be beneficial for some patients in reducing tinnitus, there is no curative therapy. Repetitive transcranial magnetic stimulation (rTMS) has been applied as a treatment for chronic tinnitus, but the effect remains controversial. MATERIAL AND METHODS: Fifty patients were treated with rTMS or placebo. Treatment consisted of 2,000 TMS pulses on each auditory cortex, at a rate of 1 Hz and an intensity of 110% of the individual motor threshold, on 5 consecutive days. rTMS and placebo effects were evaluated directly after treatment, after 1 week, and after 1, 3 and 6 months. Primary outcome was the Tinnitus Questionnaire (TQ). Secondary outcomes were the Tinnitus Handicap Inventory (THI) and a visual analogue scale. RESULTS: At none of the follow-up evaluation moments a significant difference between rTMS and placebo was observed with respect to changes in TQ or THI scores relative to pretreatment scores. Multilevel modelling (MLM) analyses did not show a global treatment effect either. Patients with a higher degree of burden showed slightly greater improvement after rTMS (only significant on the THI with MLM analyses). CONCLUSION: Bilateral low-frequency rTMS of the auditory cortex was not effective in treating tinnitus.

The effect of superior semicircular canal dehiscence on intracochlear sound pressures.

Semicircular canal dehiscence (SCD) is a pathological opening in the bony wall of the inner ear that can result in conductive hearing loss. The hearing loss is variable across patients, and the precise mechanism and source of variability are not fully understood. Simultaneous measurements of basal intracochlear sound pressures in scala vestibuli (SV) and scala tympani (ST) enable quantification of the differential pressure across the cochlear partition, the stimulus that excites the cochlear partition. We used intracochlear sound pressure measurements in cadaveric preparations to study the effects of SCD size. Sound-induced pressures in SV and ST, as well as stapes velocity and ear canal pressure were measured simultaneously for various sizes of SCD followed by SCD patching. Our results showed that at low frequencies (<600 Hz), SCD decreased the pressure in both SV and ST, as well as differential pressure, and these effects became more pronounced as dehiscence size was increased. Near 100 Hz, SV decreased by about 10 dB for a 0.5-mm dehiscence and by 20 dB for a 2-mm dehiscence, while ST decreased by about 8 dB for a 0.5-mm dehiscence and by 18 dB for a 2-mm dehiscence. Differential pressure decreased by about 10 dB for a 0.5-mm dehiscence and by about 20 dB for a 2-mm dehiscence at 100 Hz. In some ears, for frequencies above 1 kHz, the smallest pinpoint dehiscence had bigger effects on the differential pressure (10-dB decrease) than larger dehiscences (less than 10-dB decrease), suggesting larger hearing losses in this frequency range. These effects due to SCD were reversible by patching the dehiscence. We also showed that under certain circumstances such as SCD, stapes velocity is not related to how the ear can transduce sound across the cochlear partition because it is not directly related to the differential pressure, emphasizing that certain pathologies cannot be fully assessed by measurements such as stapes velocity.

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.

OBJECTIVE: To assess the change in hearing, vestibular function, and size of superior canal dehiscence (SCD) in patients with SCD syndrome over time. PATIENTS: 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). INTERVENTION: Audiometry, cVEMPs, and temporal bone CT were performed on patients with high clinical suspicion of disease progression. MAIN OUTCOME MEASURE: 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. RESULTS: 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. CONCLUSION: 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.

Cochlear implant outcomes in patients with superior canal dehiscence.

OBJECTIVE: To determine whether adult cochlear implant (CI) users with superior canal dehiscence syndrome (SCDS) or asymptomatic superior semicircular canal dehiscence (SCD) have different surgical, vestibular, and audiologic outcomes when compared to CI users with normal temporal bone anatomy. METHODS: A retrospective single institution review of CI users with either superior semicircular canal dehiscence syndrome or asymptomatic superior semicircular canal dehiscence identified eight post-lingually deafened adults with unilateral or bilateral cochlear implantation between 2006 and 2010. Preoperative and postoperative speech perception scores as well as medical and epidemiological data were recorded and analyzed. RESULTS: One patient with superior canal dehiscence syndrome and seven patients with asymptomatic superior semicircular canal dehiscence were identified, representing 7% or 8/113 of CI patients that fulfilled selection criteria. Average dehiscence length was 3.3 mm ± 0.79 SEM. Three patients received bilateral implants and five patients received a unilateral implant. Among asymptomatic superior semicircular canal dehiscence patients, subjective rates of post-operative dizziness were similar to those seen in patients with normal temporal bone anatomy (12.5 % vs. 15.9%, respectively). Speech perception abilities after surgery were poorer in SCD patients compared to the non-SCD cohort (Consonant Nucleus Consonant 33.7 ± 7.78 SEM vs. 56.7 ± 2.15 SEM P = 0.011), although both groups improved substantially relative to pre-operative performance. We also completed detailed analyses of auditory and vestibular outcomes in one patient with SCDS who underwent CI surgery in the symptomatic ear, which demonstrated preservation of vestibular function post-operatively, improved quality-of-life measures, and reduced dizziness symptomatology. CONCLUSIONS: Our data suggest that patients with asymptomatic superior canal dehiscence at the time of CI surgery have similar albeit decreased speech perception scores compared to non-SCD adult CI users. Subjective rate of dizziness or vertigo following CI surgery was similar in both asymptomatic SCD and non-SCD cohorts, with detailed analyses of a single symptomatic SCD patient revealing improved vestibular function and reduced SCD symptoms following CI.

Radiologic classification of superior canal dehiscence: implications for surgical repair.

OBJECTIVE: Surgical access to repair a superior canal dehiscence (SCD) is influenced by the location of the bony defect and its relationship to surrounding tegmen topography as seen on computed tomography. There are currently no agreed-upon methods of characterizing these radiologic findings. We propose a formal radiologic classification system of SCD based on dehiscence location and adjacent tegmen topography. STUDY DESIGN: Retrospective case review SETTING: Tertiary, neurotology referral center PATIENTS: We identified 298 patients with superior canal dehiscence on CT from February 2001 to October 2013. Of these, 251 had symptomatic superior canal dehiscence syndrome and were included in the study. INTERVENTION: Patients underwent high-resolution temporal bone CT scans with creation of axial, coronal, Pöschl, and Stenver reformatted images to examine the superior semicircular canal. Two residents-in-training and a head and neck radiologist independently read the scans. MAIN OUTCOME MEASURES: CT scans were assessed for (1) superior canal dehiscence or "near" dehiscence, (2) defect location relative to the skull base, (3) surrounding tegmen defects, (4) geniculate ganglion dehiscence, (5) superior petrosal sinus-associated dehiscence (SPS), (6) low-lying tegmen, and (7) the distance between the outer table of the temporal bone and the arcuate eminence.

Power reflectance as a screening tool for the diagnosis of superior semicircular canal dehiscence.

HYPOTHESIS: Power reflectance (PR) measurements in ears with superior canal dehiscence (SCD) have a characteristic pattern, the detection of which can assist in diagnosis. BACKGROUND: The aim of this study was to determine whether PR coupled with a novel detection algorithm can perform well as a fast, noninvasive, and easy screening test for SCD. The screening test aimed to determine whether patients with various vestibular and/or auditory symptom(s) should be further considered for more expensive and invasive tests that better define the diagnosis of SCD (and other third-window lesions). METHODS: Power reflectance was measured in patients diagnosed with SCD by high-resolution computed tomography. The study included 40 ears from 32 patients with varying symptoms (e.g., with and without conductive hearing loss, vestibular symptoms, and abnormal auditory sensations). RESULTS: Power reflectance results were compared to previously published norms and showed that SCD is commonly associated with a PR notch near 1 kHz. An analysis algorithm was designed to detect such notches and to quantify their incidence in affected and normal ears. Various notch detection thresholds yielded sensitivities of 80% to 93%, specificities of 69% to 72%, negative predictive values of 84% to 93%, and a positive predictive value of 67%. CONCLUSION: This study shows evidence that PR measurements together with the proposed notch-detecting algorithm can be used to quickly and effectively screen patients for third-window lesions such as SCD in the early stages of a diagnostic workup.

Rapid Systematic Review of the Epley Maneuver versus Vestibular Rehabilitation for Benign Paroxysmal Positional Vertigo.

OBJECTIVE: To evaluate the effectiveness of the Epley maneuver compared with vestibular rehabilitation on patient-reported symptom relief and conversion of the Dix-Hallpike from positive to negative in patients with posterior benign paroxysmal positional vertigo (p-BPPV). DATA SOURCES: PubMed, Embase, and the Cochrane Library. REVIEW METHODS: A systematic search was conducted. Studies reporting original study data were included. Relevance and risk of bias (RoB) of the selected articles were assessed. Studies with low relevance, high RoB, or both were excluded. For outcomes of interest, absolute risk differences and their 95% confidence intervals (CIs) were extracted. RESULTS: A total of 373 unique studies were retrieved. Five of these satisfied the eligibility criteria. One study with low RoB and 3 studies with moderate RoB showed that the Epley maneuver is more effective than vestibular rehabilitation at 1-week follow-up with regard to patient-reported symptom relief and conversion of the Dix-Hallpike maneuver from positive to negative (risk differences range from 10% [95% CI, 30-47] to 55% [95% CI, 35-71]). There is inconsistent evidence for the effectiveness of the Epley maneuver compared with vestibular rehabilitation at 1-month follow-up. Most studies suggest that the Epley maneuver and vestibular rehabilitation are equally effective at 1-month follow-up. CONCLUSION: The Epley maneuver is more effective in treating p-BPPV than vestibular rehabilitation at 1-week follow-up. There is inconsistent evidence for the effectiveness of the Epley maneuver compared with vestibular rehabilitation at 1-month follow-up.

Familial superior canal dehiscence syndrome.

IMPORTANCE: 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. OBSERVATIONS: 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. CONCLUSIONS AND RELEVANCE: 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.

Utility of cVEMPs in bilateral superior canal dehiscence syndrome.

OBJECTIVES/HYPOTHESIS: To determine the utility of cervical vestibular evoked myogenic potential (cVEMP) thresholds in the surgical management of bilateral superior canal dehiscence syndrome (SCDS). STUDY DESIGN: Retrospective review. METHODS: We identified patients who underwent surgical treatment for SCDS from our database of 147 patients diagnosed with superior canal dehiscence (SCD) between 2000 and 2011 at our institution. The diagnosis of SCDS was based on clinical signs and symptoms, audiometric and cVEMP testing, and high-resolution computed tomography. RESULTS: We identified 38 patients who underwent SCD surgery in 40 ears (2 bilateral). In seven patients with bilateral SCD, the more symptomatic ear had lower cVEMP thresholds, a larger air bone gap and a lateralizing tuning fork. In 13 patients with perioperative cVEMP testing, thresholds increased in 12 patients following primary repair, and no threshold shift was seen in one patient with persistence of symptoms after revision surgery. Audiometric data showed a significant mean decrease of the low-frequency air-bone gap and a mild (high-frequency) bone conduction loss after surgical repair. CONCLUSIONS: We found that, 1) preoperative cVEMP thresholds, the magnitude of the air-bone gap and tuning-fork testing are important to confirm the worse ear in patients with bilateral SCD, 2) elevation of cVEMP thresholds following surgery correlates with improvement of symptoms and underscores the importance of postoperative testing in patients with bilateral disease or recurrence of symptoms and, 3) SCD plugging is associated with a partial closure of the air-bone gap and a mild (high-frequency) sensorineural hearing loss.

Clinical factors associated with prolonged recovery after superior canal dehiscence surgery.

OBJECTIVE: To identify clinical factors associated with prolonged recovery after superior canal dehiscence surgery. STUDY DESIGN: Retrospective review. SETTING: Tertiary care academic medical center. PATIENTS: Thirty-three patients that underwent surgery for SCDS were identified from a database of 140 patients diagnosed with SCD (2000-2010) at the Massachusetts Eye and Ear Infirmary (U.S.A.). The diagnosis of SCDS was based on clinical signs and symptoms, audiometric and vestibular testing and high-resolution temporal bone computed tomography. INTERVENTION: For the primary repair, the superior canal was plugged in 31 patients through a middle fossa craniotomy approach and in 1 patient through a transmastoid approach. In 1 patient, the SCD was resurfaced through a middle fossa craniotomy approach. MAIN OUTCOME MEASURES: Postoperative clinical signs and symptoms and factors that may influence duration of disequilibrium after surgery. RESULTS: Thirty-three patients (15-71 yr; mean, 43 yr) underwent surgery for SCDS on 35 ears (2 bilateral). Mean follow-up was 28.7 months (range, 3 mo to 10 yr); 33 of 33 (100%) patients experienced initial improvement of the chief complaint. Three patients required revision surgery, improving symptoms in 2 patients. Six patients had dizziness lasting more than 4 months postoperatively, and all had bilateral SCD, migraines, and a dehiscence of 3 mm or greater. CONCLUSION: Surgical plugging of SCD is an effective management option to provide long-term improvement of the chief complaint in SCDS patients. Patients with bilateral SCD, a history of migraines, and larger defects may be at risk of prolonged recovery and should be appropriately counseled.