Probabilities of Isolated and Co-Occurring Vestibular Disorder Symptom Clusters Identified Using the Dizziness Symptom Profile.

OBJECTIVES: Dizziness is among the most common reasons people seek medical care. There are data indicating patients with dizziness, unsteadiness, or vertigo may have multiple underlying vestibular disorders simultaneously contributing to the overall symptoms. Greater awareness of the probability that a patient will present with symptoms of co-occurring vestibular disorders has the potential to improve assessment and management, which could reduce healthcare costs and improve patient quality of life. The purpose of the current investigation was to determine the probabilities that a patient presenting to a clinic for vestibular function testing has symptoms of an isolated vestibular disorder or co-occurring vestibular disorders. DESIGN: All patients who are seen for vestibular function testing in our center complete the dizziness symptom profile, a validated self-report measure, before evaluation with the clinician. For this retrospective study, patient scores on the dizziness symptom profile, patient age, and patient gender were extracted from the medical record. The dizziness symptom profile includes symptom clusters specific to six disorders that cause vestibular symptoms, specifically: benign paroxysmal positional vertigo, vestibular migraine, vestibular neuritis, superior canal dehiscence, Meniere disease, and persistent postural perceptual dizziness. For the present study, data were collected from 617 participants (mean age = 56 years, 376 women, and 241 men) presenting with complaints of vertigo, dizziness, or imbalance. Patients were evaluated in a tertiary care dizziness specialty clinic from October 2020 to October 2021. Self-report data were analyzed using a Bayesian framework to determine the probabilities of reporting symptom clusters specific to an isolated disorder and co-occurring vestibular disorders. RESULTS: There was a 42% probability of a participant reporting symptoms that were not consistent with any of the six vestibular disorders represented in the dizziness symptom profile. Participants were nearly as likely to report symptom clusters of co-occurring disorders (28%) as they were to report symptom clusters of an isolated disorder (30%). When in isolation, participants were most likely to report symptom clusters consistent with benign paroxysmal positional vertigo and vestibular migraine, with estimated probabilities of 12% and 10%, respectively. The combination of co-occurring disorders with the highest probability was benign paroxysmal positional vertigo + vestibular migraine (~5%). Probabilities decreased as number of symptom clusters on the dizziness symptom profile increased. The probability of endorsing vestibular migraine increased with the number of symptom clusters reported. CONCLUSIONS: Many patients reported symptoms of more than one vestibular disorder, suggesting their symptoms were not sufficiently captured by the symptom clusters used to summarize any single vestibular disorder covered by the dizziness symptom profile. Our results indicate that probability of symptom clusters indicated by the dizziness symptom profile is comparable to prior published work on the prevalence of vestibular disorders. These findings support use of this tool by clinicians to assist with identification of symptom clusters consistent with isolated and co-occurring vestibular disorders.

Quantitative three-dimensional image analysis of the superior canal after surgical plugging to treat superior semicircular canal dehiscence.

Surgical plugging to treat superior semicircular canal dehiscence (SCD) has been proven to impede the effect of the third mobile window, abating cochleovestibular symptoms. Knowledge of superior semicircular canal (SC)-plugging status has been proposed to serve as a guide for adjuvant treatment. Here, we investigated disturbances in the inner ear fluid space following SC plugging using a novel three-dimensional (3D) reconstruction-based method. This approach used a semi-automatic segmentation algorithm and a direct volume rendering method derived from conventional magnetic resonance images. The variable extents of filling defects at the sites of SC plugging and the positional relation of the defect to the ampulla and common crus were identified. The success group exhibited markedly reduced volumes following surgery, whereas the failure group displayed no changes in volume. These results indicate that the success or failure of SC plugging was related to 3D volume changes in the labyrinth fluid signal. Collectively, this study presents individualized SC-plugging statuses using a novel 3D reconstruction-based method and it facilitates future work regarding easy-to-measure 3D volume changes. This current technology also aids in the exploration of pathologic changes in various targets of interest.

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

OBJECTIVE: To evaluate patients who become symptomatic from superior semicircular canal dehiscence (SSCD) following head trauma. STUDY DESIGN: Case series assessing patients presenting with SSCD after a trauma. METHODS: 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). RESULTS: 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). CONCLUSION: 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. LEVEL OF EVIDENCE: 4 Laryngoscope, 131:E2810-E2818, 2021.

Dural Contact to the Malleus Head in Patients with Superior Semicircular Canal Dehiscence (SSCD): Case Series and Review of SSCD and Tegmen Defects.

OBJECTIVE: Report a series of cases in which patients have concomitant superior semicircular canal dehiscence (SSCD) and a dehiscent tegmen tympani with Dural contact to the malleus head (DCMH). METHODS: An analysis of radiologic and audiologic data in 4 patients who presented with SSCD and DCMH at a tertiary care institution. A pertinent literature review was performed. RESULTS: Four patients (5 ears) had SSCD and DCMH. In 3 patients with unilateral DCMH, the mean maximum air-bone gap was 15 dB in the ear with DCMH compared to 50 dB in the ear without DCMH. Of the 5 ears with DCMH, the mean air conduction threshold at 250 Hz was 17 dB compared to 42 dB in the 3 ears without DCMH. CONCLUSIONS: We report the findings of DCMH in a series of 4 patients with bilateral SSCD. This limited series suggests that ears with SSCD and DCMH have less of an air-bone gap than would be expected, as 1 would expect an additive effect of DCMH and SSCD on the air-bone gap.

Video-head impulse test in superior canal dehiscence.

BACKGROUND: Superior Canal Dehiscence is classically diagnosed with typical abnormalities on Vestibular Evoked Myogenic Potentials (VEMPs) and Computed Tomography (CT) scans. AIM: This paper discusses the utility of the video Head Impulse Test (vHIT) in SCD. METHODS: Data from 11 ears (8 patients) with SCD were retrospectively reviewed. Results from vHIT, VEMPs and CT and when possible, MRI scans were correlated. An audit of 300 vHIT from patients undergoing routine testing for any neurotological complaint was also conducted to look at the incidence of isolated abnormal superior canal function. RESULTS: 82% of patients (9 ears) with SCD showed abnormal vHIT (reduced gain and catch-up saccades) isolated to the affected superior semicircular canal. CONCLUSION: Correlation of the CT and VEMPs are important in forming a diagnosis of SCD. However, if isolated superior canal vHIT abnormalities are demonstrated, it is suggestive of SCD and such patients should be referred for further investigations.

Influence of Semicircular Canal Dehiscence on Cochlear Implant Outcome.

INTRODUCTION: Semicircular canal dehiscence (SCD) is defined as a defect of the bone overlying the semicircular canal. It has a relatively high prevalence of 3% in the general population, which makes it likely that a certain number of patients receiving a cochlear implant (CI) would have it. However, little is known about the influence of SCD on the CI outcome. Therefore, the aim of this study was to determine the influence of SCD on CI outcome with regard to short- and long-term word perception and hearing preservation. METHODS: This study was a retrospective analysis of postoperative word perception ability in the electric-only condition after 6, 12, and ≥18 months and of hearing preservation 4 weeks after surgery in CI recipients with and without SCD. All patients received a preoperative 1.5- or 3-tesla magnetic resonance imaging. RESULTS: Fifty-five patients were included. Forty-eight patients (87%) had no SCD, and 7 patients (13%) had SCD. Mean postoperative word perception scores were 66% in the non-SCD group versus 50% in the SCD group (p = 0.17) after 6 months, 74 versus 64% (p = 0.28) after 12 months, and 77 versus 73% (p = 0.62) after 18 or more months. The mean postoperative hearing loss in patients with functional residual hearing before surgery (n = 34) was 22 dB in the non-SCD group versus 31 dB in the SCD group (p = 0.15). CONCLUSIONS: CI outcome is comparable between recipients without and with SCD. Specifically, hearing preservation rate and word perception ability in the electric-only condition seem not affected by SCD. The rate of progress of word perception ability in the first 12 months after cochlear implantation is not influenced by SCD.

Bone-conduction hyperacusis induced by superior canal dehiscence in human: the underlying mechanism.

Our ability to hear through bone conduction (BC) has long been recognized, but the underlying mechanism is poorly understood. Why certain perturbations affect BC hearing is also unclear. An example is BC hyperacusis (hypersensitive BC hearing)-an unnerving symptom experienced by patients with superior canal dehiscence (SCD). We measured BC-evoked sound pressures in scala vestibuli (PSV) and scala tympani (PST) at the basal cochlea in cadaveric human ears, and estimated hearing by the cochlear input drive (PDIFF = PSV - PST) before and after creating an SCD. Consistent with clinical audiograms, SCD increased BC-driven PDIFF below 1 kHz. However, SCD affected the individual scalae pressures in unexpected ways: SCD increased PSV below 1 kHz, but had little effect on PST. These new findings are inconsistent with the inner-ear compression mechanism that some have used to explain BC hyperacusis. We developed a computational BC model based on the inner-ear fluid-inertia mechanism, and the simulated effects of SCD were similar to the experimental findings. This experimental-modeling study suggests that (1) inner-ear fluid inertia is an important mechanism for BC hearing, and (2) SCD facilitates the flow of sound volume velocity through the cochlear partition at low frequencies, resulting in BC hyperacusis.

The Sensitivity of the cVEMP Test in Detecting A Superior Semicircular Canal Dehiscence and the Influence of a Coexisting Incudal Lysis: A Case Report.

In this case report, the air-conducted cervical vestibular evoked myogenic potentials (AC cVEMP) test was only sensitive for the left superior semicircular canal dehiscence (SCD), even though the contralateral SCD was of equal length (2.5 mm). Furthermore, a lysis of the processus lenticularis incudis caused a real conductive hearing loss in the left ear. A diminished left AC cVEMP was thus expected, but the opposite was shown (increased corrected amplitude, lowered detection threshold). The patient only experienced hearing loss, so middle ear surgery was performed to repair the lysis. The postoperative AC cVEMP showed a further "uncovering" of the SCD with increased corrected amplitude on the left but no vestibular symptoms. The significance of an SCD should be interpreted with caution, even when the AC cVEMP and the imaging are significant. Furthermore, AC cVEMPs should not be considered as evidence for the absence or presence of conductive hearing loss.

Superior Semicircular Canal Dehiscence Syndrome.

Superior canal dehiscence syndrome (SCDS) is a vestibular disorder caused by a pathologic third window into the labyrinth that can present with autophony, sound- or pressure-induced vertigo, and chronic disequilibrium among other vestibulocochlear symptoms. Careful history taking and examination in conjunction with appropriate diagnostic testing can accurately diagnose the syndrome. Key examination techniques include fixation-suppressed ocular motor examination investigating for sound- or pressure-induced eye movements in the plane of the semicircular canal. Audiometry, vestibular evoked myogenic potentials, and computed tomography confirm the diagnosis. Corrective surgical techniques can be curative, but many patients find their symptoms are not severe enough to undergo surgery. Although a primarily peripheral vestibular disorder, as first-line consultants for most dizziness complaints, neurologists will serve their patients well by understanding SCDS and its role in the differential diagnosis of vestibular disorders.

Symptoms, Audiometric and Vestibular Laboratory Findings, and Imaging in a Concurrent Superior Canal Dehiscence Syndrome and Vestibular Schwannoma: A Case Report.

BACKGROUND: Dizziness is a common complaint that can arise from multiple systems in the body. Objective vestibular tests are used to understand the underlying function of the vestibular system and whether or not it may be contributing to the dizziness symptoms experienced by the patient. Even when comprehensive case history is consistent with an otologic etiology, audiometric and vestibular tests are ordered to objectively characterize inner ear function to help further refine the differential diagnoses and aid in guiding treatment options. Few reports in the literature describe audiometric and vestibular results in patients with multiple concurrent otologic etiologies. PURPOSE: This case provides a description of audiometric, vestibular, and imaging results in a case of concurrent bilateral superior canal dehiscence, right-sided vestibular schwannoma, and right-sided posterior canal benign paroxysmal positional vertigo. The patient's symptoms and laboratory findings are described in detail and, where appropriate, highlight challenges that may arise in interpretation. RESEARCH DESIGN: A case report. RESULTS: The patient presented for evaluation of dizziness, asymmetric hearing loss, and autophony. Comprehensive audiometric evaluation shows asymmetric sensorineural hearing loss and an air-bone gap at 250 Hz in the right ear. Vestibular evaluation shows right caloric asymmetry along with abnormal cervical vestibular- and ocular vestibular-evoked myogenic potentials, with the left ear showing results consistent with the third-window pathology. CONCLUSIONS: Comprehensive assessment of symptoms and critical thinking while performing testing are necessary when examining multiple concurrent otologic etiologies in a patient. Knowledge of anticipated test results and physiology may help the audiologist to synthesize results and make appropriate clinical recommendations as part of the multidisciplinary team.

A Comparison of Two Recording Montages for Ocular Vestibular Evoked Myogenic Potentials in Patients with Superior Canal Dehiscence Syndrome.

OBJECTIVE: The purpose of this investigation was to evaluate the sensitivity and specificity of the ocular vestibular evoked myogenic potential (oVEMP) using two electrode montages in patients with confirmed unilateral superior semicircular canal dehiscence syndrome (SCDS). STUDY DESIGN: This study evaluated oVEMP response characteristics measured using two different electrode montages from 12 unilateral SCDS ears and 36 age-matched control ears (age range = 23-66). The oVEMP responses were elicited using 500 Hz tone-burst air conduction stimuli presented at an intensity of 95 dB nHL and a rate of 5.1/sec. The two electrode montages used are described as an "infraorbital" montage and a "belly-tendon" montage. SETTING: Balance function laboratory embedded in a large, tertiary care otology clinic. RESULTS: The belly-tendon electrode montage resulted in significantly larger amplitude responses than the infraorbital electrode montage for the ears with SCDS and the normal control ears. For both electrode montages the ear with SCDS exhibited a significantly larger amplitude response, ∼50% larger than the response amplitude from the normal control ear. The belly-tendon montage additionally produced larger median increases in amplitude compared with the infraorbital montage. Specifically, the median increase in oVEMP N1-P1 amplitudes using the belly-tendon montage was 39% greater in control ears, 76% greater in the SCDS ears, and 17% greater in the contralateral SCDS ears. CONCLUSIONS: The belly-tendon electrode montage yields significantly larger oVEMP amplitude responses for participants with SCDS and normal control participants.