Posture, Gait, Quality of Life, and Hearing with a Vestibular Implant.

BACKGROUND: Bilateral vestibular hypofunction is associated with chronic disequilibrium, postural instability, and unsteady gait owing to failure of vestibular reflexes that stabilize the eyes, head, and body. A vestibular implant may be effective in alleviating symptoms. METHODS: Persons who had had ototoxic (7 participants) or idiopathic (1 participant) bilateral vestibular hypofunction for 2 to 23 years underwent unilateral implantation of a prosthesis that electrically stimulates the three semicircular canal branches of the vestibular nerve. Clinical outcomes included the score on the Bruininks-Oseretsky Test of Motor Proficiency balance subtest (range, 0 to 36, with higher scores indicating better balance), time to failure on the modified Romberg test (range, 0 to 30 seconds), score on the Dynamic Gait Index (range, 0 to 24, with higher scores indicating better gait performance), time needed to complete the Timed Up and Go test, gait speed, pure-tone auditory detection thresholds, speech discrimination scores, and quality of life. We compared participants' results at baseline (before implantation) with those at 6 months (8 participants) and at 1 year (6 participants) with the device set in its usual treatment mode (varying stimulus pulse rate and amplitude to represent rotational head motion) and in a placebo mode (holding pulse rate and amplitude constant). RESULTS: The median scores at baseline and at 6 months on the Bruininks-Oseretsky test were 17.5 and 21.0, respectively (median within-participant difference, 5.5 points; 95% confidence interval [CI], 0 to 10.0); the median times on the modified Romberg test were 3.6 seconds and 8.3 seconds (difference, 5.1; 95% CI, 1.5 to 27.6); the median scores on the Dynamic Gait Index were 12.5 and 22.5 (difference, 10.5 points; 95% CI, 1.5 to 12.0); the median times on the Timed Up and Go test were 11.0 seconds and 8.7 seconds (difference, 2.3; 95% CI, -1.7 to 5.0); and the median speeds on the gait-speed test were 1.03 m per second and 1.10 m per second (difference, 0.13; 95% CI, -0.25 to 0.30). Placebo-mode testing confirmed that improvements were due to treatment-mode stimulation. Among the 6 participants who were also assessed at 1 year, the median within-participant changes from baseline to 1 year were generally consistent with results at 6 months. Implantation caused ipsilateral hearing loss, with the air-conducted pure-tone average detection threshold at 6 months increasing by 3 to 16 dB in 5 participants and by 74 to 104 dB in 3 participants. Changes in participant-reported disability and quality of life paralleled changes in posture and gait. CONCLUSIONS: Six months and 1 year after unilateral implantation of a vestibular prosthesis for bilateral vestibular hypofunction, measures of posture, gait, and quality of life were generally in the direction of improvement from baseline, but hearing was reduced in the ear with the implant in all but 1 participant. (Funded by the National Institutes of Health and others; ClinicalTrials.gov number, NCT02725463.).

The association of hearing loss with frailty among community-dwelling older adults: findings from the National Health and Aging Trends Study.

BACKGROUND: The identification of modifiable risk factors is crucial for the prevention and/or reversal of frailty, which is associated with significant morbidity and mortality. Hearing loss affects two-thirds of older adults in the United States (U.S.) and is associated with physical and cognitive decline which may increase frailty risk. We investigated the association of hearing loss and hearing aid use with frailty and pre-frailty in a nationally representative sample of older adults in the U.S. METHODS: Cross-sectional analysis of the National Health and Aging Trends Study (2021 round). The better-hearing ear pure-tone average (BPTA) at speech-frequencies (0.5-4 kHz) was modeled continuously (per 10 dB) and categorically (no ≤ 25 dB, mild 26-40 dB, moderate or greater > 40 dB hearing loss). Hearing aid use was self-reported. The physical frailty phenotype (frail, pre-frail, robust) was determined based on Fried criteria: unintentional weight loss, exhaustion, low physical activity, weakness, slow walking speed. We used multinomial multivariable regression adjusted for sociodemographic and health characteristics (odds ratios [95% Confidence Intervals]). RESULTS: Among 2,361 participants (mean age = 81 years, 56% female, 19% Black), 860 (36%) had mild and 864 (37%) had moderate or greater hearing loss. Worse hearing was associated with greater odds of being frail versus robust (OR = 1.20 [1.05-1.38] per 10 dB difference). Categorically, moderate or greater hearing loss was associated with greater odds of being frail (OR = 1.84 [1.01-3.08]) and pre-frail (OR = 1.46 [1.01-2.10]) versus robust. Among 1,724 participants with hearing loss, compared to hearing aid users (N = 522), nonusers had greater odds of being frail (OR = 2.54 [1.54-4.18]) and pre-frail (OR = 1.51 [1.05-2.17]) versus robust, and frail versus pre-frail (OR = 1.68 [1.04-2.72]). CONCLUSIONS: In a nationally representative sample of older adults in the U.S., using gold-standard hearing measures and a validated frailty phenotype, hearing loss and lack of hearing aid use was cross-sectionally associated with frailty and pre-frailty. Future longitudinal studies are needed to establish if hearing loss is a risk factor for frailty, which may have significant clinical importance.

Characterization of patient head motion in otologic surgery: Implications for TEES.

PURPOSE: Middle ear disease is increasingly being managed via transcanal endoscopic ear surgery (TEES). A limitation of TEES is that it restricts the surgeon to single-handed dissection. One solution to this would be an endoscope holder to facilitate two-handed dissection. Current endoscope holders are stationary, and can cause potential damage from endoscope contact with the ossicles or ear canal if unintended head motion occurs from inadequate anesthetic. A dynamic device that could detect and react to patient motion would mitigate these concerns, but currently there is little formal characterization of the frequency, velocity and acceleration of unintended patient head motion during otologic procedures performed under general anesthesia. The present study aims to characterize intraoperative patient head motion kinematics during cases utilizing TEES. MATERIALS AND METHODS: This is a prospective study of adults undergoing otologic procedures performed with general anesthesia and without paralysis. Head motion was characterized using a nine-axis inertial measurement unit (IMU), (LPMS-B2, Life Performance Research) mounted to each patient's forehead for the procedure duration. RESULTS: Data was collected across 10 cases; 50% of patients were female and mean age was 50 ± 14 years. There was observed patient head motion in 40% of cases with maximum linear acceleration of 0.75 m/s2 and angular velocity of 12.50 degrees/s. CONCLUSIONS: Patient movement during otologic procedures was commonly observed, demonstrating the need for a dynamic holder to allow two-handed TEES. Results from this study are the first objective characterization of patient head motion kinematics during otologic procedures performed under general anesthesia.

Characterization of patient head motion in otologic surgery: Implications for TEES.

PURPOSE: Middle ear disease is increasingly being managed via transcanal endoscopic ear surgery (TEES). A limitation of TEES is that it restricts the surgeon to single-handed dissection. One solution to this would be an endoscope holder to facilitate two-handed dissection. Current endoscope holders are stationary, and can cause potential damage from endoscope contact with the ossicles or ear canal if unintended head motion occurs from inadequate anesthetic. A dynamic device that could detect and react to patient motion would mitigate these concerns, but currently there is little formal characterization of the frequency, velocity and acceleration of unintended patient head motion during otologic procedures performed under general anesthesia. The present study aims to characterize intraoperative patient head motion kinematics during cases utilizing TEES. MATERIALS AND METHODS: This is a prospective study of adults undergoing otologic procedures performed with general anesthesia and without paralysis. Head motion was characterized using a nine-axis inertial measurement unit (IMU), (LPMS-B2, Life Performance Research) mounted to each patient's forehead for the procedure duration. RESULTS: Data was collected across 10 cases; 50% of patients were female and mean age was 50 ± 14 years. There was observed patient head motion in 40% of cases with maximum linear acceleration of 0.75 m/s2 and angular velocity of 12.50 degrees/s. CONCLUSIONS: Patient movement during otologic procedures was commonly observed, demonstrating the need for a dynamic holder to allow two-handed TEES. Results from this study are the first objective characterization of patient head motion kinematics during otologic procedures performed under general anesthesia.

Sudden Hearing Loss with Vertigo Portends Greater Stroke Risk Than Sudden Hearing Loss or Vertigo Alone.

BACKGROUND: Because it is unknown whether sudden hearing loss (SHL) in acute vertigo is a "benign" sign (reflecting ear disease) or a "dangerous" sign (reflecting stroke), we sought to compare long-term stroke risk among patients with (1) "SHL with vertigo," (2) "SHL alone," and (3) "vertigo alone" using a large national health-care database. METHODS: Patients with first-incident SHL (International Classification of Diseases, Ninth Edition, Clinical Modification [ICD-9-CM] 388.2) or vertigo (ICD-9-CM 386.x, 780.4) were identified from the National Health Insurance Research Database of Taiwan (2002-2009). We defined SHL with vertigo as a vertigo-related diagnosis ±30 days from the index SHL event. SHL without a temporally proximate vertigo diagnosis was considered SHL alone. The vertigo-alone group had no SHL diagnosis. All the patients were followed up until stroke, death, withdrawal from the database, or current end of the database (December 31, 2012) for a minimum period of 3 years. The hazards of stroke were compared across groups. RESULTS: We studied 218,656 patients (678 SHL with vertigo, 1998 with SHL alone, and 215,980 with vertigo alone). Stroke rates at study end were 5.5% (SHL with vertigo), 3.0% (SHL alone), and 3.9% (vertigo alone). Stroke hazards were higher in SHL with vertigo than in SHL alone (hazard ratio [HR], 1.93; 95% confidence interval [CI], 1.28-2.91) and in vertigo alone (HR, 1.63; 95% CI, 1.18-2.25). Defining a narrower window between SHL and vertigo (±3 days) increased the hazards. CONCLUSIONS: The combination of SHL plus vertigo in close temporal proximity is associated with increased subsequent stroke risk over SHL alone and vertigo alone. This suggests that SHL in patients with vertigo is not necessarily a benign peripheral vestibular sign.

Optimizing ocular vestibular evoked myogenic potential testing for superior semicircular canal dehiscence syndrome: electrode placement.

OBJECTIVE: To compare the sensitivity and specificity of ocular vestibular evoked myogenic potentials (oVEMPs) using 2 electrode montages for the diagnosis of superior canal dehiscence syndrome (SCDS). SUBJECTS: 16 SCDS patients (17 affected-SCDS ears, 15 contralateral-SCDS ears) and 12 controls (24 ears). METHODS: oVEMPs were recorded in response to 500-Hz tone bursts using 2 electrode montages. For both montages the active electrode was placed approximately 5 mm below each eye and a ground electrode on the sternum. For montage 1 (standard), the reference electrode was centered 2 cm below each active electrode. For montage 2, the reference electrode was placed on the chin. RESULTS: For either montage, the separation between oVEMP amplitudes in affected-SCDS ears and controls was significant (p < 0.001), with excellent sensitivity and specificity (>90%). CONCLUSION: oVEMP recordings with the standard montage remain a reliable method for evaluation of SCDS.

Superior Canal Dehiscence and the Risk of Additional Dehiscences: A Retrospective CT Cohort Study.

OBJECTIVE: Determine if superior canal dehiscence (SCD) found on flat-panel CT increases the risk for other defects in the otic capsule. STUDY DESIGN: Retrospective cohort study. SETTING: Tertiary care center. PATIENTS: One hundred ears (50 with SCD and 50 matched controls without SCD). INTERVENTIONS: Flat-panel CT imaging. MAIN OUTCOME MEASURES: (1) Prevalence of other dehiscences in SCD ears, (2) dehiscences in controls, and (3) otic capsule thickness in other reported dehiscence locations (cochlea-carotid, lateral semicircular canal [SCC] and mastoid, facial nerve-lateral SCC, vestibular aqueduct, posterior SCC-jugular bulb, posterior SCC-posterior fossa). Between-group comparisons were considered significant at p < 0.007 after applying the Bonferroni correction for multiple comparisons. RESULTS: Not including the SCD, there was a mean of 0.04 additional dehiscences in the SCD group (n = 2/50, 4%) and 0.04 non-SCD dehiscences in the controls (n = 2/50, 4%, p > 0.007). In the SCD group, there was one dehiscence between the cochlea and carotid artery and one between the posterior SCC and posterior fossa. The control group had one enlarged vestibular aqueduct and one dehiscence between the facial nerve and lateral SCC. As a group, SCD ears had wider vestibular aqueducts (0.68 ± 0.20 vs 0.51 ± 0.30 mm, p < 0.007) and thinner bone between the posterior SCC and posterior fossa (3.12 ± 1.43 vs 4.34 ± 1.67 mm, p < 0.007). The bone between the facial nerve and lateral SCC was thicker in SCD ears (0.77 ± 0.23 vs 0.55 ± 0.27 mm, p < 0.007) and no different for cochlea-carotid, and lateral SCC and mastoid (p > 0.007). CONCLUSIONS: SCD does not increase the likelihood of a second dehiscence in the same otic capsule. SCD patients may have congenitally thinner otic capsule bones compared to controls, particularly near the posterior SCC, where the vestibular aqueduct may be enlarged.

Quality of Popular Online Resources About Vestibular Migraine.

Objective: To evaluate the readability, understandability, actionability, and accuracy of online resources covering vestibular migraine (VM). Study Design: Cross-sectional descriptive study design. Setting: Digital collection of websites appearing on Google search. Methods: Google searches were conducted to identify common online resources for VM. We examined readability using the Flesch Reading Ease (FRE) and Flesch-Kincaid Grade Level scores, understandability and actionability using the Patient Education Materials Assessment Tool (PEMAT), and accuracy by comparing the website contents to the consensus definition of "probable vestibular migraine." Results: Eleven of the most popular websites were analyzed. Flesch-Kincaid Grade Level averaged at a 13th-grade level (range: 9th-18th). FRE scores averaged 35.5 (range: 9.1-54.4). No website had a readability grade level at the US Agency for Healthcare Research and Quality recommended 5th-grade level or an equivalent FRE score of 90 or greater. Understandability scores varied ranging from 49% to 88% (mean 70%). Actionability scores varied more, ranging from 12% to 87% (mean 44%). There was substantial inter-rater agreement for both PEMAT understandability scoring (mean κ = 0.76, SD = 0.08) and actionability scoring (mean κ = 0.65, SD = 0.08). Three sites included all 3 "probable vestibular migraine" diagnostic criteria as worded in the consensus statement. Conclusion: The quality of online resources for VM is poor overall in terms of readability, actionability, and agreement with diagnostic criteria.

Traumatic Events Preceding the Development of Superior Canal Dehiscence Syndrome.

OBJECTIVE: To describe the features of antecedent head trauma in patients with superior canal dehiscence syndrome (SCDS). STUDY DESIGN: Cross-sectional survey. SETTING: Tertiary referral center. METHODS: An online survey was sent to 450 adult patients who underwent surgical repair for SCDS patients asking questions about the nature of internal or external traumatic events preceding symptoms. RESULTS: One-hundred and thirty-six patients (avg. age, 51.9 years, 62.8% female) completed the survey, of which 61 (44.9%) described either preceding external head trauma (n = 35, 26%), preceding internal pressure event (n = 33, 25%), or both (8, 6%). Of those endorsing external trauma, 22 (63%) described a singular event (head hit by object (n = 8); head hit ground (n = 5); motor vehicle accident (n = 4); assault (n = 2); other (n = 3). One-third experienced loss of consciousness because of the trauma. For those describing internal pressure events (n = 33), the most common events were heavy physical exertion (9, 27%); pressure changes while flying (6, 18%); coughing, nose blowing with illness (5, 15%); childbirth (5, 15%); and self contained underwater breathing apparatus diving events (3, 9%). The interval between trauma and onset of symptoms averaged 5.6 years (SD, 10.7 years). One-third (n = 19) described onset of symptoms immediately after the external trauma or internal pressure event. Symptoms began on the side ipsilateral to the trauma in 91%. Sound- and pressure-induced vertigo/oscillopsia developed more commonly after external trauma versus internal pressure events (68% and 61% vs 44% and 32%, respectively). CONCLUSION: Trauma or internal pressure-related events precede SCDS symptoms in nearly half of cases, with roughly half of preceding events being external.

Patient-Reported Outcomes After Vestibular Implantation for Bilateral Vestibular Hypofunction.

Importance: Standard-of-care treatment proves inadequate for many patients with bilateral vestibular hypofunction (BVH). Vestibular implantation is an emerging alternative. Objective: To examine patient-reported outcomes from prosthetic vestibular stimulation. Design, Setting, and Participants: The Multichannel Vestibular Implant (MVI) Early Feasibility Study is an ongoing prospective, nonrandomized, single-group, single-center cohort study conducted at Johns Hopkins Hospital that has been active since 2016 in which participants serve as their own controls. The study includes adults with severe or profound adult-onset BVH for at least 1 year and inadequate compensation despite standard-of-care treatment. As of March 2023, 12 candidates completed the eligibility screening process. Intervention: The MVI system electrically stimulates semicircular canal branches of the vestibular nerve to convey head rotation. Main Outcomes and Measures: Patient-reported outcome instruments assessing dizziness (Dizziness Handicap Inventory [DHI]) and vestibular-related disability (Vestibular Disorders-Activities of Daily Living [VADL]). Health-related quality of life (HRQOL) assessed using the Short Form-36 Utility (SF36U) and Health Utilities Index Mark 3 (HUI3), from which quality-adjusted life-years were computed. Results: Ten individuals (5 female [50%]; mean [SD] age, 58.5 [5.0] years; range, 51-66 years) underwent unilateral implantation. A control group of 10 trial applicants (5 female [50%]; mean [SD] age, 55.1 [8.5] years; range, 42-73 years) completed 6-month follow-up surveys after the initial application. After 0.5 years of continuous MVI use, a pooled mean (95% CI) of within-participant changes showed improvements in dizziness (DHI, -36; 95% CI, -55 to -18), vestibular disability (VADL, -1.7; 95% CI, -2.6 to -0.7), and HRQOL by SF36U (0.12; 95% CI, 0.07-0.17) but not HUI3 (0.02; 95% CI, -0.22 to 0.27). Improvements exceeded minimally important differences in the direction of benefit (exceeding 18, 0.65, and 0.03, respectively, for DHI, VADL, and SF36U). The control group reported no mean change in dizziness (DHI, -4; 95% CI, -10 to 2), vestibular disability (VADL, 0.1; 95% CI, -0.9 to 1.1) or HRQOL per SF36U (0; 95% CI, -0.06 to 0.05) but an increase in HRQOL per HUI3 (0.10; 95% CI, 0.04-0.16). Lifetime HRQOL gain for MVI users was estimated to be 1.7 quality-adjusted life-years (95% CI, 0.6-2.8) using SF36U and 1.4 (95% CI, -1.2 to 4.0) using HUI3. Conclusions and Relevance: This cohort study found that vestibular implant recipients report vestibular symptom improvements not reported by a control group. These patient-reported benefits support the use of vestibular implantation as a treatment for bilateral vestibular hypofunction.

Transmastoid galvanic stimulation does not affect the vergence-mediated gain increase of the human angular vestibulo-ocular reflex.

Vergence is one of several viewing contexts that require an increase in the angular vestibular-ocular reflex (aVOR) response. A previous monkey study found that the vergence-mediated gain (eye/head velocity) increase of the aVOR was attenuated by 64 % when anodic currents, which preferentially lower the activity of irregularly firing vestibular afferents, were delivered to both labyrinths. We sought to determine whether there was similar evidence implicating a role for irregular afferents in the vergence-mediated gain increase of the human aVOR. Our study is based upon analysis of the aVOR evoked by head rotations, delivered passively while subjects viewed a near (15 cm) or far (124 cm) target and applying galvanic vestibular stimulation (GVS) via surface electrodes. We tested 12 subjects during 2-3 sessions each. Vestibular stimuli consisted of passive whole-body rotations (sinusoids from 0.05-3 Hz and 12-25°/s, and transients with peak ~15°, 50°/s, 500°/s(2)) and head-on-body impulses (peak ~30°, 150°/s, 3,000°/s(2)). GVS was on for 10 s every 20 s. All polarity combinations were tested, with emphasis on uni- and bi-lateral anodic inhibition. The average stimulus current was 5.9 ± 1.6 mA (range: 3-9.5 mA), vergence angle (during near viewing) was 22.6 ± 2.8° and slow-phase eye velocity caused by left anodic current stimulation with head stationary was -3.4 ± 1.1°/s, -0.2 ± 0.6°/s and 2.5 ± 1.4°/s (torsion, vertical, horizontal). No statistically significant GVS effects were observed, suggesting that surface electrode GVS has no effect on the vergence-mediated gain increase of the aVOR at the current levels (~6 mA) tolerated by most humans. We conclude that clinically practical transmastoid GVS does not effectively silence irregular afferents and hypothesize that currents >10 mA are needed to reproduce the monkey results.

Cochlear Aqueduct Morphology in Superior Canal Dehiscence Syndrome.

The cochlear aqueduct (CA) connects the scala tympani to the subarachnoid space and is thought to assist in pressure regulation of perilymph in normal ears, however, its role and variation in inner ear pathology, such as in superior canal dehiscence syndrome (SCDS), is unknown. This retrospective radiographic investigation compared CA measurements and classification, as measured on flat-panel computerized tomography, among three groups of ears: controls, n = 64; anatomic superior canal dehiscence without symptoms (SCD), n = 28; and SCDS, n = 64. We found that in a multinomial logistic regression adjusted for age, sex, and BMI, an increase in CA length by 1 mm was associated with a lower odds for being in the SCDS group vs. control (Odds ratio 0.760 p = 0.005). Hierarchical clustering of continuous CA measures revealed a cluster with small CAs and a cluster with large CAs. Another multinomial logistic regression adjusted for the aforementioned clinical covariates showed an odds ratio of 2.97 for SCDS in the small CA cluster as compared to the large (p = 0.004). Further, no significant association was observed between SCDS symptomatology-vestibular and/or auditory symptoms-and CA structure in SCDS ears. The findings of this study lend support to the hypothesis that SCDS has a congenital etiology.

Augmented Reality in Otology/Neurotology: A Scoping Review with Implications for Practice and Education.

OBJECTIVE: To determine how augmented reality (AR) has been applied to the field of otology/neurotology, examine trends and gaps in research, and provide an assessment of the future potential of this technology within surgical practice and education. DATA SOURCES: PubMed, EMBASE, and Cochrane Library were assessed from their inceptions through October 2022. A manual bibliography search was also conducted. REVIEW METHODS: A scoping review was conducted and reported according to PRISMA-ScR guidelines. Data from studies describing the application of AR to the field of otology/neurotology were evaluated, according to a priori inclusion/exclusion criteria. Exclusion criteria included non-English language articles, abstracts, letters/commentaries, conference papers, and review articles. RESULTS: Eighteen articles covering a diverse range of AR platforms were included. Publication dates spanned from 2007 to 2022 and the rate of publication increased over this time. Six of 18 studies were case series in human patients although the remaining were proof of concepts in cadaveric/artificial/animal models. The most common application of AR was for surgical navigation (14 of 18 studies). Computed tomography was the most common source of input data. Few studies noted potential applications to surgical training. CONCLUSION: Interest in the application of AR to otology/neurotology is growing based on the number of recent publications that use a broad range of hardware, software, and AR platforms. Large gaps in research such as the need for submillimeter registration error must be addressed prior to adoption in the operating room and for educational purposes. LEVEL OF EVIDENCE: N/A Laryngoscope, 133:1786-1795, 2023.

Detection and Quantification of Calcitonin Gene-Related Peptide (CGRP) in Human Plasma Using a Modified Enzyme-Linked Immunosorbent Assay.

Calcitonin gene-related peptide (CGRP) is a vasoactive neuropeptide that plays a putative role in the pathophysiology of migraine headaches and may be a candidate for biomarker status. CGRP is released from neuronal fibers upon activation and induces sterile neurogenic inflammation and arterial vasodilation in the vasculature that receives trigeminal efferent innervation. The presence of CGRP in the peripheral vasculature has spurred investigations to detect and quantify this neuropeptide in human plasma using proteomic assays, such as the enzyme-linked immunosorbent assay (ELISA). However, its half-life of 6.9 min and the variability in technical details of assay protocols, which are often not fully described, have yielded inconsistent CGRP ELISA data in the literature. Here, a modified ELISA protocol for the purification and quantification of CGRP in human plasma is presented. The procedural steps involve sample collection and preparation, extraction using a polar sorbent as a means of purification, additional steps to block non-specific binding, and quantification via ELISA. Further, the protocol has been validated with spike and recovery and linearity of dilution experiments. This validated protocol can theoretically be used to quantify CGRP concentrations in the plasma of individuals not only with migraine, but also with other diseases in which CGRP may play a role.

Otolith Membrane Herniation, not Semicircular Canal Duct Dilation, Is Associated with Decreased Caloric Responses in Ménière's Disease.

Ménière's disease (MD) is a debilitating disorder with unclear pathophysiology whose diagnosis often relies on clinical judgment rather than objective testing. To complicate matters further, a dissociation has emerged between two vestibular function tests commonly used in patients with MD to examine the same end-organ (the semicircular canals): the caloric test and video head impulse testing (vHIT). Caloric responses are often abnormal, while vHIT results remain normal. Explaining this dissociation could reveal novel insights into MD pathophysiology. Here, we conduct a histopathological study using temporal bone specimens (N = 58, 21 MD-affected ears and 37 age-matched controls) and their clinical testing data to examine current hypotheses aimed at this dissociation. We find otolith membrane herniation into the horizontal semicircular canal in 69% of MD ears, with 90% of these ears demonstrating a diminished caloric response. No ears with a normal response had this herniation. Moreover, we evaluated the semicircular canals for endolymphatic hydrops, which had been hypothesized to contribute to the dissociation, and found no evidence of duct dilation/hydrops. We did, however, note a potentially novel morphologic finding-smaller bony labyrinth cross-sectional diameters/areas in some MD ear canals compared to controls, suggesting relative size of the membranous duct to the bony canal rather than absolute size may be of importance. Taken together, this study refines hypotheses on the vestibular test dissociation in MD, holding diagnostic implications and expanding our understanding of the mechanisms underlying this enigmatic disease.

Vestibular Implantation Can Work Even After More Than 20 Years of Bilateral Vestibular Hypofunction.

OBJECTIVE: To determine whether prosthetic stimulation delivered via a vestibular implant can elicit artificial sensation of head movement despite long (23-yr) duration adult-onset ototoxic bilateral vestibular hypofunction (BVH). STUDY DESIGN: Case report. SETTING: Tertiary care center as part of a first-in-human clinical trial. PATIENTS: One. INTERVENTIONS: Unilateral vestibular implantation with an investigational multichannel vestibular implant in a 55-year-old man with a well-documented 23-year history of aminoglycoside-induced BVH. MAIN OUTCOME MEASURES: Electrically evoked vestibulo-ocular reflexes (eeVOR). RESULTS: Vestibular implant stimulation can drive stimulus-aligned eeVOR and elicit a vestibular percept 23 years after the onset of bilateral vestibulopathy. Prosthetic stimulation targeting individual semicircular canals elicited eye movements that approximately aligned with each targeted canal's axis. The magnitude of the eeVOR response increased with increasing stimulus current amplitude. Response alignment and magnitude were similar to those observed for implant recipients who underwent vestibular implantation less than 10 years after BVH onset. Responses were approximately stable for 18 months of continuous device use (24 h/d except during sleep). CONCLUSIONS: Vestibular implantation and prosthetic electrical stimulation of semicircular canal afferent nerves can drive canal-specific eye movement responses more than 20 years after the onset of ototoxic vestibular hypofunction.

2D Measurements of the Angle of the Vestibular Aqueduct Using CT Imaging.

Recently, Bächinger et al. developed a software that measures the angle between the vestibular aqueduct proximal to the vestibule and the distal vestibular aqueduct on computed tomography (CT) scans and found differences in the vestibular aqueduct angle between the hypoplastic and degenerative categories of Meniere's disease (MD). Hypoplastic radiological findings were associated with the development of bilateral MD and hypoplastic changes were not found outside of fetal temporal bones and individuals with MD. The purpose of this study is to examine how the software developed by Bächinger et al. performs when applied to a large dataset of adult patients with varied otologic diagnoses. Adult patients who underwent high resolution flat panel CT scans without intravenous contrast (n = 301) were retrospectively reviewed. Measurements of the angle of the vestibular aqueduct were made using the previously developed software tool. The tool could be applied to measure the vestibular aqueduct angle in most CT scans of the temporal bones (n = 572 ears, 95%). While the majority of ears fell within the normal range of <120 degrees (n = 462, 80%), fourteen ears (2.3%) in 13 patients were found to have vestibular aqueduct angles that meet criteria for hypoplastic MD (>140 degrees). Only one of the 13 patients had a diagnosis of MD and not in the ear in the hypoplastic category. An inconsistent pattern of other otologic diagnoses were found among the 13 individuals meeting criteria for hypoplastic MD. Although prior reports indicate the software has prognostic value in individuals with MD, these results suggest that the software may have lower positive predictive value when applied to a large population of individuals with varied otologic diagnoses.

Predictive Factors for Concurrent Tegmen Dehiscence in Superior Canal Dehiscence Syndrome.

OBJECTIVES: To describe factors predictive of tegmen dehiscence in subjects with superior semicircular canal dehiscence syndrome (SCDS). STUDY DESIGN: Retrospective case series. SETTING: Tertiary referral center. PATIENTS: Subjects with SCDS who underwent middle fossa craniotomy (MFC) for plugging/resurfacing. MAIN OUTCOME MEASURES: Operative and radiographic findings of tegmen dehiscences, preoperative low frequency air-bone gaps (LF-ABGs), ocular vestibular evoked myogenic potential (oVEMP) amplitudes, size of superior semicircular canal dehiscence (SCD), and history of obesity or obstructive sleep apnea (OSA). RESULTS: One hundred thirty six patients (avg. age, 50.6 yr, 55.1% female) underwent MFC for repair of SCDS. Tegmen dehiscences were commonly found intraoperatively (tegmen tympani dehiscence [TTD] in 19.9% [11% with dural contact of ossicles], tegmen mastoideum dehiscence [TMD] in 28.7%). There were no differences in preoperative LF-ABGs and preoperative oVEMP amplitudes with respect to tegmen status. The sensitivity and specificity of computed tomography (CT) for predicting an intraoperatively confirmed TTD was 85 and 74%, respectively, and 44 and 79% for TMD. History of obesity and OSA did not differ between those with and without tegmen dehiscences. The presence of contralateral SCD and increasing cross-sectional area of SCD were both significantly associated with concurrent tegmen defects. CONCLUSIONS: Obesity, OSA, preoperative oVEMP, and LF-ABG do not differ between those with SCD alone and those with SCD and concurrent tegmen dehiscences. Likewise, CT scans have relatively low sensitivity for identifying tegmen dehiscences. The presence of concurrent tegmen defects is more common in subjects with larger SCD cross-sectional areas and contralateral SCD.

Combined Arterial and Venous Phase Computed Tomographic Imaging of the Skull Base in Pulsatile Tinnitus.

OBJECTIVE: To describe the demographic, clinical, and radiologic findings in a consecutive series of patients presenting with a chief complaint of pulsatile tinnitus (PT). STUDY DESIGN: Retrospective review of 157 patients undergoing a combined arterial/venous phase computed tomographic (CT) imaging study. SETTING: Tertiary referral center. PATIENTS: Adult patients referred to neurotology faculty for evaluation of PT between 2016 and 2020. INTERVENTIONS: Triple phase high-resolution arteriography/venography/temporal bone CT. MAIN OUTCOME MEASURES: Prevalence of osseous, venous, and/or arterial pathology, clinicodemographic characteristics. RESULTS: One hundred fifty-seven adults (mean age, 52 years; 79.6% female) were evaluated. A history of migraine headaches was common (19.7%). The average body mass index was 30.0 (standard deviation, 6.8), and 17.2% of subjects had a diagnosis of obstructive sleep apnea. Idiopathic intracranial hypertension was diagnosed by elevated opening pressure on lumbar puncture in 13.4%. Comorbid depression and anxiety were common (25.5% and 26.1%, respectively). Overall, abnormalities were found in 79.0% of scans, with bilateral transverse sinus stenosis (TSS) seen in 38.9% and unilateral TSS found in 20.4%. Fifteen subjects (9.6%) had evidence of osseous etiologies, including superior canal dehiscence or thinning in 8.9% and sigmoid sinus dehiscence in one subject. There were 3 dural arteriovenous fistulae identified. Unilateral PT was ipsilateral to the side of TSS in 84.4% of subjects with unilateral TSS. CONCLUSION: In a large consecutive series of patients with PT referred for CT venography/arteriography, transverse sinus stenosis was the most common finding at 59%. Venous etiologies for PT should be suspected when patients are referred to neurotologists for evaluation.

Ataxia telangiectasia: a "disease model" to understand the cerebellar control of vestibular reflexes.

Experimental animal models have suggested that the modulation of the amplitude and direction of vestibular reflexes are important functions of the vestibulocerebellum and contribute to the control of gaze and balance. These critical vestibular functions have been infrequently quantified in human cerebellar disease. In 13 subjects with ataxia telangiectasia (A-T), a disease associated with profound cerebellar cortical degeneration, we found abnormalities of several key vestibular reflexes. The vestibuloocular reflex (VOR) was measured by eye movement responses to changes in head rotation. The vestibulocollic reflex (VCR) was assessed with cervical vestibular-evoked myogenic potentials (cVEMPs), in which auditory clicks led to electromyographic activity of the sternocleidomastoid muscle. The VOR gain (eye velocity/head velocity) was increased in all subjects with A-T. An increase of the VCR, paralleling that of the VOR, was indirectly suggested by an increase in cVEMP amplitude. In A-T subjects, alignment of the axis of eye rotation was not with that of head rotation. Subjects with A-T thus manifested VOR cross-coupling, abnormal eye movements directed along axes orthogonal to that of head rotation. Degeneration of the Purkinje neurons in the vestibulocerebellum probably underlie these deficits. This study offers insights into how the vestibulocerebellum functions in healthy humans. It may also be of value to the design of treatment trials as a surrogate biomarker of cerebellar function that does not require controlling for motivation or occult changes in motor strategy on the part of experimental subjects.