David A. Zapala

A comparison of water and air caloric responses and their ability to distinguish between patients with normal and impaired ears.

Objectives: The caloric test is a mainstay of modern vestibular assessment. Yet caloric test methods have not been well standardized, and normal response values have not been universally agreed upon. The air caloric test has been particularly problematic. In this article, we present our efforts to establish a population-based description of the caloric response evoked by water and air stimuli at both cool and warm temperatures. Design: Data were collected from a retrospective record review of patients who underwent caloric testing at Mayo Clinic Jacksonville between 2002 and 2006. Two subgroups were identified. One group was found to have no vestibulopathy after comprehensive medical investigation. The second group was found to have severe bilateral vestibular weakness; this diagnosis was based on medical evaluation and objective test results. Caloric response distributions and associated probability estimates were developed from each group. Results: A total of 2587 medical records were found to contain caloric response data. Of these, 693 patients met the criteria to be classified as having no identifiable vestibulopathy (otologically normal patients with normal caloric responses). Sixty-eight patients met the criteria for bilateral vestibular weakness (reduced or absent rotatory chair responses). Our analysis yielded the following results: (1) there were differences between nystagmus distributions across stimuli. On average, the magnitude of cool water (30°C) maximum slow-phase velocities was smaller than those from warm water (44°C). Maximum slow-phase velocity distributions from cool (21°C) and warm (51°C) air stimuli were more similar to each other than were responses to water stimuli and fell between the water distributions. (2) Combined metrics (combined eye speed and total eye speed) were comparable for water and air stimuli. (3) Response distributions from otologically normal patients were different from those of patients with bilateral vestibular weakness. (4) Derived probability estimates allowed for quantification of caloric response normal limits, sensitivity, specificity, and error rates. Conclusions: Current bithermal test methods assume an equivalence of caloric response strength from warm and cool stimuli. Our results show standard cool and warm water stimuli provoke substantially different response magnitudes, with warm stimuli provoking stronger responses. When calibrated as described herein, air stimuli perform comparably with water stimuli for bithermal caloric test purposes, with more uniform and less variable response distributions. Both air- and water-based tests were able to distinguish between normal and abnormally weak ears with sensitivity and specificity values between 0.82 and 0.84. We advocate for the calibration of all caloric stimuli based on the test’s statistical performance and not arbitrary assumptions about stimulus equivalence.

Love and Fear of Heights: The Pathophysiology and Psychology of Height Imbalance

Abstract Individual psychological responses to heights vary on a continuum from acrophobia to height intolerance, height tolerance, and height enjoyment. This paper reviews the English literature and summarizes the physiologic and psychological factors that generate different responses to heights while standing still in a static or motionless environment. Perceptual cues to height arise from vision. Normal postural sway of 2 cm for peripheral objects within 3 m increases as eye-object distance increases. Postural sway >10 cm can result in a fall. A minimum of 20 minutes of peripheral retinal arc is required to detect motion. Trigonometry dictates that a 20-minute peripheral retinal arch can no longer be achieved in a standing position at an eye-object distance of >20 m. At this distance, visual cues conflict with somatosensory and vestibular inputs, resulting in variable degrees of imbalance. Co-occurring deficits in the visual, vestibular, and somatosensory systems can significantly increase height imbalance. An individuals psychological makeup, influenced by learned and genetic factors, can influence reactions to height imbalance. Enhancing peripheral vision and vestibular, proprioceptive, and haptic functions may improve height imbalance. Psychotherapy may improve the troubling subjective sensations to heights.

Cartilage cap occlusion technique for dehiscent superior semicircular canals

Objective: Assessment of a cartilage cap occlusion of dehiscent superior semicircular canals via a transmastoid and tegmen mini-craniotomy approach surgical technique. Study Design: Retrospective case review. Setting: Tertiary referral center. Patients: Thirty-seven patients over a 2 year time period underwent cartilage cap occlusion of a dehiscent superior semicircular canal. Intervention: Therapeutic. Main Outcome Measure: Subjective improvement and/or resolution of dizziness postoperatively. Results: Of 37 patients, 29 (78%) felt much better and had resolution of their dizziness. Of 37 patients, 5 (14%) felt some definite improvement, although not complete resolution. Two patients (5%) felt their dizziness was neither better nor worse, and 1 patient (3%) felt dizziness was worse after surgery. Conclusion: The cartilage cap occlusion technique of dehiscent superior semicircular canals via a transmastoid and tegmen mini-craniotomy approach is a good option for managing symptomatic patients with a dehiscent superior semicircular canal.

Oculo-vestibular recoupling using galvanic vestibular stimulation to mitigate simulator sickness.

INTRODUCTION Despite improvement in the computational capabilities of visual displays in flight simulators, intersensory visual-vestibular conflict remains the leading cause of simulator sickness (SS). By using galvanic vestibular stimulation (GVS), the vestibular system can be synchronized with a moving visual field in order to lessen the mismatch of sensory inputs thought to result in SS. METHODS A multisite electrode array was used to deliver combinations of GVS in 21 normal subjects. Optimal electrode combinations were identified and used to establish GVS dose-response predictions for the perception of roll, pitch, and yaw. Based on these data, an algorithm was then implemented in flight simulator hardware in order to synchronize visual and GVS-induced vestibular sensations (oculo-vestibular-recoupled or OVR simulation). Subjects were then randomly exposed to flight simulation either with or without OVR simulation. A self-report SS checklist was administered to all subjects after each session. An overall SS score was calculated for each category of symptoms for both groups. RESULTS The analysis of GVS stimulation data yielded six unique combinations of electrode positions inducing motion perceptions in the three rotational axes. This provided the algorithm used for OVR simulation. The overall SS scores for gastrointestinal, central, and peripheral categories were 17%, 22.4%, and 20% for the Control group and 6.3%, 20%, and 8% for the OVR group, respectively. CONCLUSIONS When virtual head signals produced by GVS are synchronized to the speed and direction of a moving visual field, manifestations of induced SS in a cockpit flight simulator are significantly reduced.

Vestibular evoked myogenic potentials in patients with vestibular migraine.

Objective Literature investigating otolith reflexes in patients with vestibular migraine (VM) is variable and primarily describes the descending saccular pathway. This research aimed to study ocular vestibular evoked myogenic potential (oVEMP) and cervical vestibular evoked myogenic potential (cVEMP) prevalence and response characteristics in patients with suspected VM and in control patients. The purpose is to assess vulnerabilities within the ascending utricular and descending saccular pathways in the VM population. Study Design Retrospective study Setting Tertiary academic referral center Patients 39 adults with VM, 29 control patients Main Outcome Measure(s) Air conducted oVEMPs and cVEMPs measured with 500 Hz tone burst stimuli Results Age of headache onset was most often in childhood or adolescence, with dizziness onset occurring later. The rate of bilaterally absent oVEMPs was significantly higher (28%, p < 0.01) in the VM group compared with the control group (0%). oVEMP amplitude asymmetry ratios were significantly higher for the definite VM (p < 0.01) and probable VM (p = 0.023) groups than the control group. Eleven patients also had history of concussion; they were significantly more likely to demonstrate bilaterally absent oVEMPs (p < 0.01) in comparison to the control patients. When VM patients with a history of concussion were omitted from analysis, differences in oVEMP amplitude asymmetry (p < 0.01) and bilateral oVEMP absence remained significant (p = 0.015). There were no differences in the rate of bilateral cVEMP presence or response parameters between VM and control groups. Conclusion VEMP presentation differs for some patients diagnosed with VM. The higher rates of abnormal oVEMPs may suggest greater vulnerability within the ascending utricular–ocular pathway in patients with VM.

Dizziness handicap after cartilage cap occlusion for superior semicircular canal dehiscence.

Objective 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). Study Design Repeated measures, retrospective chart review. Setting Tertiary referral center. Patients Twenty patients over a 2-year period who underwent surgical repair of SCD using the cartilage cap occlusion technique. Intervention Therapeutic. Main Outcome Measure Preoperative and postoperative Dizziness Handicap Inventory (DHI) questionnaires were completed (median, interquartile range). Results 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). Conclusion 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.

Safety of Audiology Direct Access for Medicare Patients Complaining of Impaired Hearing

BACKGROUND Allowing Medicare beneficiaries to self-refer to audiologists for evaluation of hearing loss has been advocated as a cost-effective service delivery model. Resistance to audiology direct access is based, in part, on the concern that audiologists might miss significant otologic conditions. PURPOSE To evaluate the relative safety of audiology direct access by comparing the treatment plans of audiologists and otolaryngologists in a large group of Medicare-eligible patients seeking hearing evaluation. RESEARCH DESIGN Retrospective chart review study comparing assessment and treatment plans developed by audiologists and otolaryngologists. STUDY SAMPLE 1550 records comprising all Medicare eligible patients referred to the Audiology Section of the Mayo Clinic Florida in 2007 with a primary complaint of hearing impairment. DATA COLLECTION AND ANALYSIS Assessment and treatment plans were compiled from the electronic medical record and placed in a secured database. Records of patients seen jointly by audiology and otolaryngology practitioners (Group 1: 352 cases) were reviewed by four blinded reviewers, two otolaryngologists and two audiologists, who judged whether the audiologist treatment plan, if followed, would have missed conditions identified and addressed in the otolaryngologists treatment plan. Records of patients seen by audiology but not otolaryngology (Group 2: 1198 cases) were evaluated by a neurotologist who judged whether the patient should have seen an otolaryngologist based on the audiologists documentation and test results. Additionally, the audiologist and reviewing neurotologist judgments about hearing asymmetry were compared to two mathematical measures of hearing asymmetry (Charing Cross and AAO-HNS [American Academy of Otolaryngology-Head and Neck Surgery] calculations). RESULTS In the analysis of Group 1 records, the jury of four judges found no audiology discrepant treatment plans in over 95% of cases. In no case where a judge identified a discrepancy in treatment plans did the audiologist plan risk missing conditions associated with significant mortality or morbidity that were subsequently identified by the otolaryngologist. In the analysis of Group 2 records, the neurotologist judged that audiology services alone were all that was required in 78% of cases. An additional 9% of cases were referred for subsequent medical evaluation. The majority of remaining patients had hearing asymmetries. Some were evaluated by otolaryngology for hearing asymmetry in the past with no interval changes, and others were consistent with noise exposure history. In 0.33% of cases, unexplained hearing asymmetry was potentially missed by the audiologist. Audiologists and the neurotologist demonstrated comparable accuracy in identifying Charing Cross and AAO-HNS pure-tone asymmetries. CONCLUSIONS Of study patients evaluated for hearing problems in the one-year period of this study, the majority (95%) ultimately required audiological services, and in most of these cases, audiological services were the only hearing health-care services that were needed. Audiologist treatment plans did not differ substantially from otolaryngologist plans for the same condition; there was no convincing evidence that audiologists missed significant symptoms of otologic disease; and there was strong evidence that audiologists referred to otolaryngology when appropriate. These findings are consistent with the premise that audiology direct access would not pose a safety risk to Medicare beneficiaries complaining of hearing impairment.

The effect of galvanic vestibular stimulation on distortion product otoacoustic emissions

Galvanic stimulation has long been used as a nonmechanical means of activating the vestibular apparatus through direct action on the vestibular nerve endings. This stimulation has been reported to be safe, but no studies have examined the potential changes in the corresponding cochlear receptors. The aim of the present study was to evaluate the effect of galvanic vestibular stimulation (GVS) on distortion product otoacoustic emissions (DPOAEs). Fourteen subjects underwent DPOAEs during several conditions of GVS. The DPOAEs ranged from ∼ 1 kHz to ∼ 8 kHz at 65/55 dB for f1/f2 and with an f2/f1 ratio of 1.2. The subjects were evaluated at 10 stimulation conditions that ranged from -2.0 mA to +2.0 mA for each frequency. Statistical analysis showed no significant differences in DPOAE amplitudes for all conditions with and without GVS. Results also showed no significant differences between DPOAE amplitudes before and after GVS. Multivariate analysis found subject variability in DPOAE amplitude, which was not thought to be GVS related. Results indicated that GVS produced neither temporary nor permanent changes in DPOAEs.

Development and Initial Validation of a Consumer Questionnaire to Predict the Presence of Ear Disease

Importance The already large population of individuals with age- or noise-related hearing loss in the United States is increasing, yet hearing aids remain largely inaccessible. The recent decision by the US Food and Drug Administration to not enforce the medical examination prior to hearing aid fitting highlights the need to reengineer consumer protections when increasing accessibility. A self-administered tool to estimate ear disease risk would provide disease surveillance without posing an unreasonable barrier to hearing aid procurement. Objective To develop and validate a consumer questionnaire for the self-assessment of risk for ear diseases associated with hearing loss. Design, Setting, and Participants The questionnaire was developed using established methods including expert opinion to validate and create questions, and cognitive interviews to ensure that questions were clear to respondents. Exploratory structural equation modeling, logistic regression, and receiver operating characteristic curve analysis were used to determine sensitivity and specificity with blinded neurotologist opinion as the criterion for evaluation. Patients 40 to 80 years old with ear or hearing complaints necessitating a neurotologic examination and a control group of participants with a diagnosis of age- or noise-related hearing loss participated at the Departments of Otorhinolaryngology and Audiology of Mayo Clinic Florida. Main Outcomes and Measures Sensitivity and specificity of the prototype questionnaire to identify individuals with targeted diseases. Results Of 307 participants (mean [SD] age, 62.9 [9.8] years; 148 [48%] female), 75% (n = 231) were enrolled with targeted disease(s) identified on neurotologic assessment and 25% (n = 76) with age- or noise-related hearing loss. Participants were randomly divided into a training sample (80% [n = 246; 185 with disease, 61 controls]) and a test sample (20% [n = 61; 46 with disease, 15 controls]). Using a simple scoring method, a sensitivity of 94% (95% CI, 89%-97%) and specificity of 61% (95% CI, 47%-73%) were established in the training sample. Applying this cutoff to the test sample resulted in 85% (95% CI, 71%-93%) sensitivity and 47% (95% CI, 22%-73%) specificity. Conclusions and Relevance This is the first self-assessment tool designed to assess an individual’s risk for ear disease. Our preliminary results demonstrate a high sensitivity to disease detection. A further validated and refined version of this questionnaire may serve as an efficacious tool for improving access to hearing health care while minimizing the risk for missed ear diseases.

Identifying and Prioritizing Diseases Important for Detection in Adult Hearing Health Care

PURPOSE The purpose of this research note is to identify and prioritize diseases important for detection in adult hearing health care delivery systems. METHOD Through literature review and expert consultation, the authors identified 195 diseases likely to occur in adults complaining of hearing loss. Five neurotologists rated the importance of disease on 3 dimensions related to the necessity of detection prior to adult hearing aid fitting. RESULTS Ratings of adverse health consequences, diagnostic difficulty, and presence of nonotologic symptoms associated with these diseases resulted in the identification of 104 diseases potentially important for detection prior to adult hearing aid fitting. CONCLUSIONS Current and evolving health care delivery systems, including direct-to-consumer sales, involve inconsistent means of disease detection vigilance prior to device fitting. The first steps in determining the safety of these different delivery methods are to identify and prioritize which diseases present the greatest risk for poor health outcomes and, thus, should be detected in hearing health care delivery systems. Here the authors have developed a novel multidimensional rating system to rank disease importance. The rankings can be used to evaluate the effectiveness of alternative detection methods and to inform public health policy. The authors are currently using this information to validate a consumer questionnaire designed to accurately identify when pre- fitting medical evaluations should be required for hearing aid patients.