Oculomotor and Perceptual Measures of Visual Motion Sensitivity in Patients With Chronic Dizziness Symptoms.

OBJECTIVE: The purpose of this study was to provide empirical data describing the relationship between behavioral responses to dynamic visual motion in adults with chronic dizziness symptoms with and without clinically identifiable peripheral vestibular impairment. DESIGN: Prospective, quasi-experimental study including individuals with chronic dizziness symptoms with identified unilateral peripheral vestibular impairment (n=27), and individuals with chronic dizziness symptoms without identified vestibular impairment (n=26). We measured (a) visual perception of verticality in a dynamic background, (b) postural displacement in a dynamic background, (c) eye movement behaviors in various visual contexts, and (d) self-rating degree of anxiety. RESULTS: Status of peripheral vestibular function was not a significant predictor of behavioral responses to visual motion. The data show that the ability to fixate on a visual target was predictive of postural control in a dynamic visual background. Trial-to-trial variability in verticality responses and degree of self-rated anxiety were also associated with postural control. CONCLUSIONS: Apart from vestibular function, oculomotor control is important for maintaining control of whole-body motor responses during exposure to a dynamic visual stimulus. Vertical perception precision-not accuracy-may be more important for understanding real-world consequences of visual motion sensitivity. Traditional diagnostic evaluations focusing exclusively on characterizing the peripheral vestibular system may not provide insight into the behaviors associated with visual motion sensitivity.

Development and Preliminary Findings of the Dizziness Symptom Profile.

OBJECTIVES: Dizziness, vertigo, and unsteadiness are common complaints of patients who present to primary care providers. These patients often are referred to otology for assessment and management. Unfortunately, there are a small number of specialists to manage these patients. However, there are several dizziness disorders that can be successfully managed by primary care providers if the disorder is properly identified. To assist in the identification of several of the most common dizziness disorders, we developed the dizziness symptom profile (DSP). The DSP is a self-report questionnaire designed to generate one or more differential diagnoses that can be combined with the patient's case history and physical examination. DESIGN: This report describes three investigations. Investigations 1 and 2 (i.e., exploratory and confirmatory investigations, N = 514) describe the development of the DSP. Investigation 3 (N = 195) is a validation study that describes the level of agreement between the DSP completed by the patient, and, the differential diagnosis of the otologist. RESULTS: The final version of the DSP consists of 31 items. Preliminary findings suggest that the DSP is in agreement with the differential diagnoses of ear specialists for Meniere's disease (100% agreement), vestibular migraine (95% agreement), and benign paroxysmal positional vertigo (82% agreement). CONCLUSIONS: Early results suggest that DSP may be useful in the creation of differential diagnoses for dizzy patients that can be evaluated and managed locally. This has the potential to reduce the burden on primary care providers and reduce delays in the diagnosis of common dizziness and vertigo disorders.

Examination of Utricular Response Using oVEMP and Unilateral Centrifugation Rotation Testing.

OBJECTIVES: Significant advancements have been made toward the clinical assessment of utricular function through ocular vestibular-evoked myogenic potentials (oVEMP) and unilateral centrifugation (UCF) testing. To date, no study has examined intrasubject relationships between these measures. The study hypothesis was that intrasubject responses from oVEMP and UCF testing would be correlated inasmuch as both tests have been reported to assess utricular function. DESIGN: UCF rotations and oVEMP testing were performed on healthy volunteers, aged 18 to 62 years. A within-subject study design compared and correlated UCF outcome measures of ocular counterroll, subjective visual vertical, and ocular counterroll-gravitational inertial acceleration slope against peak to peak oVEMP N1-P1 amplitude. RESULTS: Correlational analyses failed to reveal any significant relationships between oVEMP amplitude and UCF responses suggesting that these tests may be inciting different response properties within the utricular system. CONCLUSIONS: Various anatomical and physiological differences within the utricle, in addition to the fundamental differences in stimulus properties between the oVEMP and UCF tests, could explain the lack of significant correlations between these measures and suggest that oVEMP and UCF testing may be complimentary in their evaluation of the utricular system. These data reinforce the complexities of the utricular system and provide further insight into the difficulties encountered in its clinical assessment.

Predictive properties of the video head impulse test: measures of caloric symmetry and self-report dizziness handicap.

OBJECTIVES: The purpose of this investigation was to determine whether a predictable relationship existed between self-reported dizziness handicap and video Head Impulse Test (vHIT) results in a large sample of patients reporting to a dizziness clinic. Secondary objectives included describing the characteristics of the vHIT ipsilesional and contralesional vestibulo-ocular reflex slow-phase velocity in patients with varying levels of canal paresis. Finally, the authors calculated the sensitivity and specificity of the vHIT for detecting horizontal semicircular canal impairment using the caloric test as the "gold standard." DESIGN: Participants were 115 adults presenting to a tertiary medical care center with symptoms of dizziness. Participants were administered a measure of self-report dizziness handicap (i.e., Dizziness Handicap Inventory) and underwent caloric testing and vHIT at the same appointment. RESULTS: Results showed that (1) there were no significant group differences (i.e., vHIT normal versus vHIT abnormal) in the Dizziness Handicap Inventory total score, (2) both ipsilesional and contralateral velocity gain decreased with increases in caloric paresis, and (3) a caloric asymmetry of 39.5% was determined to be the cutoff that maximized discrimination of vHIT outcome. CONCLUSIONS: The level of self-reported dizziness handicap is not predicted by the outcome of the vHIT, which is consistent with the majority of published reports describing the poor relationship between quantitative tests of vestibular function and dizziness handicap. Further, the study findings have demonstrated that vHIT and caloric data are not redundant, and each test provides unique information regarding the functional integrity of the horizontal semicircular canal at different points on the frequency spectrum. The vHIT does offer some advantages over caloric testing, but at the expense of sensitivity. The vHIT can be completed in less time, is not noxious to the patient, and requires very little laboratory space. However, the study data show that a caloric asymmetry of 39.5% is required to optimize discrimination between an abnormal and normal vHIT. It is the authors' contention that the vHIT is a complementary test to the balance function examination and should viewed as such rather than as a replacement for caloric testing.

Development of an Automated Triage System for Longstanding Dizzy Patients Using Artificial Intelligence.

Objective: To report the first steps of a project to automate and optimize scheduling of multidisciplinary consultations for patients with longstanding dizziness utilizing artificial intelligence. Study Design: Retrospective case review. Setting: Quaternary referral center. Methods: A previsit self-report questionnaire was developed to query patients about their complaints of longstanding dizziness. We convened an expert panel of clinicians to review diagnostic outcomes for 98 patients and used a consensus approach to retrospectively determine what would have been the ideal appointments based on the patient's final diagnoses. These results were then compared retrospectively to the actual patient schedules. From these data, a machine learning algorithm was trained and validated to automate the triage process. Results: Compared with the ideal itineraries determined retrospectively with our expert panel, visits scheduled by the triage clinicians showed a mean concordance of 70%, and our machine learning algorithm triage showed a mean concordance of 79%. Conclusion: Manual triage by clinicians for dizzy patients is a time-consuming and costly process. The formulated first-generation automated triage algorithm achieved similar results to clinicians when triaging dizzy patients using data obtained directly from an online previsit questionnaire.

Effects of age on the tuning of the cVEMP and oVEMP.

OBJECTIVES: The purpose of the present investigation was to define for young, middle-aged, and older adults the optimal frequency (cies) to record both the cervical vestibular-evoked myogenic potential (cVEMP) and the ocular vestibular-evoked myogenic potential (oVEMP). Further, this study aimed to describe age-related changes in the tuning of these two vestibular-evoked myogenic potentials. DESIGN: This was a prospective study. Participants were 39 healthy adults (mean age 46.3 ± 15.7 years; range = 22 to 78 years; 15 men) equally divided into 3 age groups of 13 participants each: young adult (18 to 39 years), middle age (40 to 59 years), and old adult (≥60 years). cVEMPs and oVEMPs were recorded using air-conduction tone bursts at stimulus frequencies of 125, 250, 500, 750, 1000, 1500, and 2000 Hz presented at 127 dB pSPL. RESULTS: There was a significant main effect of age group and frequency on the amplitude of both the cVEMP and the oVEMP. Amplitudes were largest for the Young adult group for the cVEMP and for the young adult and Middle age group for the oVEMP. The largest average peak-to-peak amplitude occurred in response to a 750 Hz tone burst for both responses. No significant differences in mean amplitude of the cVEMP or oVEMP were observed for 500, 750, or 1000 Hz stimuli. There was a significant interaction of age group and frequency for the cVEMP, suggesting a loss of tuning for the old adult group. Compared with the young adult group, the tuning of the cVEMP and oVEMP for the older adjults appeared to shift to a higher frequency. CONCLUSION: There is no sharp tuning in the saccule and utricle. Instead, there is a range of best frequencies that may be used to evoke the cVEMP and oVEMP responses. The results of the present investigation also demonstrate that the optimal stimulus frequency to elicit a VEMP may change with age. Accordingly, 500 Hz may not be the ideal frequency to elicit VEMPs for all age groups. For this reason, in cases where the VEMP response is absent at 500 Hz it is recommended that attempts be made to record the VEMP for tone-burst frequencies of 750 or 1000 Hz.

The effects of amplitude normalization and EMG targets on cVEMP interaural amplitude asymmetry.

OBJECTIVES: The purpose of this investigation was to determine whether the use of visual feedback of tonic electromyographic (EMG) activity, or the use of amplitude normalization techniques would reduce significantly the variability in cervical vestibular evoked myogenic potential (cVEMP) P13-N23 interaural amplitude asymmetry data in otologically and neurologically intact children and adults. DESIGN: There were 97 subjects, both pediatric and adult, from whom the authors recorded cVEMPs with and without the use of an EMG target and amplitude normalization techniques. The four conditions were: (1) conventional recording (condition 1), (2) conventional recording with an EMG target (condition 2), (3) same as condition 1, with the addition of postacquisition amplitude normalization techniques, and (4) same as condition 2, with the addition of postacquisition amplitude normalization techniques. The absolute peak to peak amplitude of positive-negative response (P13-N23), absolute latency of P13, and the left or right amplitude asymmetry of P13-N23 were measured. RESULTS: Neither P13-N23 amplitudes nor latencies, neither mean root mean square (RMS) of the full wave rectified EMG activity, nor the standard deviation of the RMS EMG activity differed significantly when subjects were, and were not, asked to ensure their tonic EMG activity exceeded a visual target (i.e., representing >50 µV RMS EMG). Amplitude normalization of the cVEMP waveforms failed to reduce significantly the variability in the amplitude asymmetry data. CONCLUSIONS: Activating the sternocleidomastoid muscle with the patient in a semirecumbent position, with head turned away from the stimulated ear and head elevated (i.e., an optimal activation technique) was sufficient to produce the highest amplitude cVEMPs with an acceptable amount of variability in subjects of all ages. Group data suggested that the use of visual targets and amplitude normalization routines did not reduce significantly the variability in cVEMP interaural amplitude asymmetry measures. However, in isolated cases amplitude normalization converted an "abnormal" cVEMP into a "normal" cVEMP although the reverse occurred as well, suggesting that these techniques may be beneficial for a subset of patients receiving a less than perfectly administered test procedure.

Electrocochleography in the diagnosis of third window conditions.

Introduction: Superior semicircular canal dehiscence (SSCD) is the best-known and most common presentation of so-called "third window conditions." There are a variety of diagnostic measures and tests for this condition in the current literature, including air-bone gap, vestibular-evoked myogenic potentials, and electrocochleography (EcochG). The purpose of this study was to investigate the diagnostic utility of EcochG and its relationship to air-bone gap in a cohort of patients with confirmed SSCD. Methods: We reviewed data from 20 patients (11 female and 9 male subjects, age ranging 21-78 years), with confirmed unilateral or bilateral superior canal dehiscence. In total, 11 patients had unilateral SSCD and 9 patients had bilateral SSCD as determined by high-resolution CT scan. This resulted in the inclusion of twenty-nine ears with superior canal dehiscence and 11 normal ears. Results: Our results indicated that all confirmed SSCD ears presented with an abnormal EcochG SP/AP value and that there was a statistically significant difference between normal and dehiscent ears. There was no statistically significant relationship between air-bone gap and SP/AP ratio in the ears diagnosed with SSCD nor was there a significant difference between dehiscent and normal ears in terms of air-bone gap at three frequencies. Discussion: These results are consistent with previous studies showing the diagnostic utility of EcochG for this condition and the variability of air-bone gap. While an unexpected air-bone gap continues to be a red flag for SSCD, its absence along with the presence of subjective symptoms is a reasonable indicator for further clinical investigation to include EcochG.

Effect of Sound Source Location and Spatial Hearing on the Vestibulo-Ocular Reflex.

BACKGROUND: There have been conflicting results on the effect of auditory stimulation on the vestibulo-ocular reflex (VOR) with some studies indicating suppression, enhancement, or no effect. No studies to date have assessed the effect of sound source location on VOR gain or the relationship between spatial hearing ability and VOR gain. PURPOSE: The purpose of the present study was to determine if VOR gain was affected by moving the location of the sound source within participants and to determine if these effects were related to spatial hearing ability. RESEARCH DESIGN: A between subjects repeated measures experimental design was utilized. STUDY SAMPLE: Two groups of participants (adult and child) with normal otologic, vestibular, and neurologic function. 22 adults (20 female and 2 male; average age = 23 years) and 16 children (9 female and 7 male; average age = 7.5 years) were included in data analysis. DATA COLLECTION AND ANALYSIS: VOR gain was measured using rotational chair stimulation in the following auditory conditions: silent, insert earphones, external loudspeaker at 0° azimuth rotating with participant, and external stationary speaker. Localization ability was measured using root mean square (RMS) error. RESULTS: Results indicated a significant effect for sound source location on VOR gain and VOR difference gain in both groups. RMS error was positively correlated for the moving and fixed sound source locations for both adults and children. CONCLUSION: VOR gain was significantly affected by location of the sound source. Findings suggest the presence and location of an auditory stimulus during rotational testing can alter results during the assessment.

Outcomes and Patient Experience in Individuals With Longstanding Dizziness.

PURPOSE: This study aimed to describe the relationship between changes in pre and post self-perceived dizziness handicap, scores on the patient health questionnaire, and perceptions of patient's value of being evaluated and managed by a multidisciplinary team. METHOD: Seventy-eight patients completed the Dizziness Handicap Inventory (DHI) and Patient Health Questionnaire-Fourth Edition (PHQ-4) questionnaires post multidisciplinary clinical consultations and testing for the chief complaints of dizziness, unsteadiness, vertigo, or balance problems. The diagnoses of each patient were recorded from the clinical reports of each specialty consultation and were classified as structural, functional, or psychiatric. They were contacted by phone at least 6 months after their visit to obtain feedback regarding their symptoms and overall patient experience. RESULTS: The change in DHI total score did not differ significantly by diagnosis (p = .56), indicating that patients experienced an improvement in DHI total score regardless of diagnosis. PHQ-4 anxiety scores worsened by a mean of 0.7 points for those with structural diagnoses (p = .04), improved by a mean of 0.7 points for psychiatric diagnoses (p = .16), and improved by a mean of 0.3 points for functional diagnoses (p = .39). Only seven patients would not recommend the team to a family or friend; these patients tended to report worsening DHI total scores (p = .27) compared to the significant improvement in DHI total scores for patients who would make such a recommendation (p < .001). Similarly, only 13 patients did not feel the information they received had a positive impact; these patients tended to report worsening DHI total scores (p = .18) compared to the significant improvement in DHI total scores for patients who did feel the information had a positive impact (p < .001). DISCUSSION: The assessment and management of patients with chronic dizziness is challenging due to symptoms arising from multiple etiologies. Our finding of a vast difference between high satisfaction and relatively unchanged dizziness handicap suggests that there is value in seeing a multidisciplinary team where consultations are unhurried, care is coordinated, and expectations regarding treatment can be managed.

Development and validation of a new disease-specific quality of life instrument for sporadic vestibular schwannoma: the Mayo Clinic Vestibular Schwannoma Quality of Life Index.

OBJECTIVE: Facial nerve function, hearing preservation, and tumor control have been the primary benchmarks used to assess vestibular schwannoma (VS) outcomes. Acknowledging the frequent discrepancy between what physicians prioritize and what patients value, there has been increasing prioritization of patient-reported outcome measures when evaluating the impact of VS diagnosis and its treatment. Motivated by reported limitations of prior instruments used to assess quality of life (QOL) in patients with VS, the authors describe the development and validation of a new disease-specific QOL measure: the Vestibular Schwannoma Quality of Life (VSQOL) Index. METHODS: The content development phase comprised identification of clinically important domains and prioritization of feelings or concerns individuals with VS may have. The validation phase encompassed determining how items were grouped into domains and eliminating redundant items. Both phases leveraged data from cross-sectional and longitudinal surveys, expertise from a multidisciplinary working group, and patients with a broad range of experiences with VS (n = 42 during content development and n = 263 during validation). Domain scores from the new instrument were assessed for reliability and correlation with other measures of similar constructs. RESULTS: The VSQOL Index consists of 40 items that evaluate the impact of VS diagnosis and its management on QOL, treatment satisfaction, and employment and is estimated to take 8-10 minutes to complete. Domain scores range from 0 (worst) to 100 (best) and demonstrate excellent psychometric properties, including content, construct, and convergent validity and both internal consistency (Cronbach's alphas 0.83 to 0.91) and test-retest reliability (reliability coefficients 0.86 to 0.96). CONCLUSIONS: The VSQOL Index is a valid and reliable measure that overcomes several limitations of prior instruments, including omission or underrepresentation of domains that frequently impact well-being, such as pain, cognition, satisfaction or regret surrounding treatment decisions, and occupational limitations, to comprehensively evaluate the impact of VS diagnosis or its treatment on QOL.

Characterization of Postural Sway in Patients With Persistent Postural-Perceptual Dizziness (PPPD) Using Wearable Motion Sensors.

OBJECTIVE: To extend previous investigations of postural control in patients with persistent-postural perceptual dizziness (PPPD). STUDY DESIGN: Case-controlled, cross-sectional, observational investigation. SETTING: Tertiary care center. PATIENTS: Fifteen patients with PPPD, 15 control volunteers. INTERVENTIONS: Measurement of anterior-posterior (AP) and medial-lateral (ML) sway at the waist using wearable accelerometers during posturography; assessment of reach and gait. MAIN OUTCOME MEASURES: Peak-to-peak AP and ML sway displacement on the six conditions of the Sensory Organization Test (SOT); Scores on the SOT, Functional Reach Test (FRT), and Dynamic Gait Index (DGI). RESULTS: Compared to control volunteers, patients with PPPD had significantly greater sway displacement at the waist in the AP direction in SOT conditions 3, 5, and 6 and in the ML direction in SOT conditions 2 and 4, resulting in significantly lower median equilibrium scores on the composite index and all six SOT conditions. Patients with PPPD had significantly lower scores on the FRT and DGI that were not correlated with SOT performance. AP sway in conditions 3 and 6 differentiated patients with PPPD from controls with high sensitivity (≥0.87) and specificity (≥0.87). CONCLUSIONS: This study replicated previous work showing poor SOT performance by patients with PPPD who had greater AP sway associated with visual dependence and greater ML sway in low demand conditions than controls. Patients with PPPD also performed poorer on the FRT and DGI, but lack of correlation with SOT scores suggested different mechanisms of impairment in postural control, reach, and ambulation. AP sway demonstrated potential as a diagnostic marker.

Insensitivity of the "Romberg test of standing balance on firm and compliant support surfaces" to the results of caloric and VEMP tests.

OBJECTIVE: The objective of this study was to assess the sensitivity, specificity, and positive and negative predictive value of the Romberg Test of Standing Balance on Firm and Compliant Support Surfaces (RTSBFCSS) for the identification of patients with vestibular system impairments affecting the horizontal semicircular canal, saccule, and/or inferior and superior vestibular nerves. The RTSBFCSS was developed for the National Health and Nutrition Examination Survey (NHANES) and was used recently to estimate the numbers of individuals aged 40 yr or older with vestibular system impairments among the general population of the United States. DESIGN: A retrospective analysis of the medical records of 103 consecutive patients aged 40 yr or older (mean age 59 ± 12 yr, 71 females) who had undergone vestibular assessment at the Balance Disorders Clinic at the Vanderbilt University School of Medicine. Patients with complete electro- or videonystagmography testing, cervical vestibular evoked myogenic potential (cVEMP) testing, and the RTSBFCSS screening test were included in the analysis. A series of 2 × 2 tables were created that represented the number of "true positives," "true negatives," "false positives," and "false negatives" of the RTSBFCSS under conditions where the caloric test was abnormal and then separately where the cVEMP test was abnormal. The data were analyzed in a manner such that sensitivity, specificity, and both positive and negative predictive value of the RTSBFCSS could be calculated. RESULTS: When the caloric test was used as the criterion standard and the subject selection criteria in the NHANES study were used (i.e., subjects who were able to maintain postural stability for trials 1-3 of the RTSBFCSS; N = 45), the sensitivity and specificity of the RTSBFCSS to impairment of the horizontal semicircular canal or superior vestibular nerve were 55% and 64%, respectively, yielding positive and negative predictive values of 55% and 64%, respectively. When all patients aged 40 yr or older were evaluated (N = 103), the sensitivity and specificity were 61% and 58%, respectively, yielding positive and negative predictive values of 39% and 78%, respectively. Using the cVEMP test as the criterion standard for the detection of impairment affecting the saccule and/or inferior vestibular nerve did not improve the performance criteria of the NHANES screening measure. CONCLUSIONS: The RTSBFCSS should not be used as a screening measure for vestibular impairment.

Normal characteristics of the ocular vestibular evoked myogenic potential.

BACKGROUND: Stimulus-evoked electromyographic changes can be recorded from the extraocular muscles. These short-latency negative-polarity evoked myogenic potentials are called ocular vestibular evoked myogenic potentials (oVEMPs). To date there has not yet been a large-scale study examining the effects of age on the amplitude, latency, threshold, and interaural differences of the oVEMP to air-conducted stimuli. Further, before the oVEMP can become a useful clinical tool, the test-retest reliability of the response must be established. The oVEMP response, once more completely understood, may provide diagnostic information that is complementary to the cervical vestibular evoked myogenic potential (cVEMP; i.e., sternocleidomastoid muscle). PURPOSE: To describe the normal characteristics of oVEMP in a cohort of age-stratified subjects, to assess the test-retest reliability of the oVEMP, and to determine if reference contamination occurs using a common recommended infraorbital reference electrode derivation. RESEARCH DESIGN: A prospective, descriptive study design was used for an investigation with a threefold purpose in which oVEMP recordings were made from the extraocular muscles (e.g., inferior oblique muscle). STUDY SAMPLE: Fifty otologically and neurologically normal adults and children served as subjects. Subjects ranged in age from 8 to 88 yr. DATA COLLECTION AND ANALYSIS: In Investigation 1, oVEMPs were recorded from the ipsilateral and contralateral inferior oblique muscles for all subjects. The stimulus was a 95 dB nHL 500 Hz tone burst. Next, oVEMP thresholds were obtained. Amplitude, latency, and thresholds were tabulated, and descriptive statistics were used to calculate normative values. Age-related differences in oVEMP component latencies, amplitudes, interaural amplitude asymmetries (IAAs), and thresholds were determined using an analysis of variance. In Investigation 2, oVEMPs were recorded twice in 10 subjects, once (test) and once approximately 10 weeks later (retest). Test-retest reliability for the oVEMP peak-to-peak amplitude, n1 latency, p1 latency, n1 threshold, and IAA were assessed with intraclass correlation coefficients (ICCs) calculated using a two-way random-effects, absolute-agreement model. In Investigation 3, a four-channel oVEMP recording was conducted in 10 subjects. Both observational methods and paired-sample t-tests were used to evaluate the effect that reference electrode location had on the oVEMP. RESULTS: oVEMP responses were present bilaterally in 90% of our subjects. The upper limit of oVEMP amplitude asymmetry, defined as the mean plus two standard deviations, was 34% (mean = 14%, SD 10), and the mean n1 latency was 12.5 (SD 1.0) msec. The amplitude of the response significantly decreased and the threshold significantly increased with increasing age, with the greatest age effects occurring in subjects 50 yr and older. Test-retest reliability was acceptable (ICCs for the measurement variables ranged from .53 to .87). Using conventional recommended recording techniques, evidence of reference contamination occurred for all subjects, resulting in a mean amplitude reduction of 30% (range = 18%-43%). CONCLUSIONS: Age results in systematic changes in oVEMP measurement parameters. The test-retest reliability is acceptable, and reference contamination averaging 30% is guaranteed using a second infraorbital electrode as the inverting input (i.e., reference electrode) for bipolar recordings. The oVEMP can be used as a complementary diagnostic tool to the cVEMP in evaluating subjects with suspected peripheral vestibular disorders.

The influence of unilateral saccular impairment on functional balance performance and self-report dizziness.

BACKGROUND: Postural stability in humans is largely maintained by vestibular, visual, and somatosensory inputs to the central nervous system. Recent clinical advances in the assessment of otolith function (e.g., cervical and ocular vestibular evoked myogenic potentials [cVEMPs and oVEMPs], subjective visual vertical [SVV] during eccentric rotation) have enabled investigators to identify patients with unilateral otolith impairments. This research has suggested that patients with unilateral otolith impairments perform worse than normal healthy controls on measures of postural stability. It is not yet known if patients with unilateral impairments of the saccule and/or inferior vestibular nerve (i.e., unilaterally abnormal cVEMP) perform differently on measures of postural stability than patients with unilateral impairments of the horizontal SCC (semicircular canal) and/or superior vestibular nerve (i.e., unilateral caloric weakness). Further, it is not known what relationship exists, if any, between otolith system impairment and self-report dizziness handicap. PURPOSE: The purpose of this investigation was to determine the extent to which saccular impairments (defined by a unilaterally absent cVEMP) and impairments of the horizontal semicircular canal (as measured by the results of caloric testing) affect vestibulospinal function as measured through the Sensory Organization Test (SOT) of the computerized dynamic posturography (CDP). A secondary objective of this investigation was to measure the effects, if any, that saccular impairment has on a modality-specific measure of health-related quality of life. RESEARCH DESIGN: A retrospective cohort study. Subjects were assigned to one of four groups based on results from balance function testing: Group 1 (abnormal cVEMP response only), Group 2 (abnormal caloric response only), Group 3 (abnormal cVEMP and abnormal caloric response), and Group 4 (normal control group). STUDY SAMPLE: Subjects were 92 adult patients: 62 were seen for balance function testing due to complaints of dizziness, vertigo, or unsteadiness, and 30 served as controls. INTERVENTION: All subjects underwent videonystagmography or electronystagmography (VNG/ENG), vestibular evoked myogenic potentials (VEMPs), self-report measures of self-perceived dizziness disability/handicap (Dizziness Handicap Inventory), and tests of postural control (Neurocom Equitest). DATA COLLECTION AND ANALYSIS: Subjects were categorized into one of four groups based on balance function test results. All variables were subjected to a multifactor analysis of variance (ANOVA). The Dizziness Handicap Inventory (DHI) total scores and equilibrium scores served as the dependent variables. RESULTS: Results showed that patients with abnormal unilateral saccular or inferior vestibular nerve function (i.e., abnormal cVEMP) demonstrated significantly impaired postural control when compared to normal participants. However, this group demonstrated significantly better postural stability when compared to the group with abnormal caloric responses alone and the group with abnormal caloric responses and abnormal cVEMP results. Patients with an abnormal cVEMP did not differ significantly on the DHI compared to the other two impaired groups. CONCLUSIONS: We interpret these findings as evidence that a significantly asymmetrical cVEMP in isolation negatively impacts performance on measures of postural control compared to normal subjects but not compared to patients with significant caloric weaknesses. However, patients with a unilaterally abnormal cVEMP do not differ from patients with significant caloric weaknesses in regard to self-perceived dizziness handicap.

Patterns of abnormality in cVEMP, oVEMP, and caloric tests may provide topological information about vestibular impairment.

BACKGROUND: The cervical vestibular evoked myogenic potential (cVEMP) is recorded from the sternocleidomastoid muscle (SCM) and represents a stimulus-evoked attenuation of electromyographic (EMG) activity following activation of the saccule and inferior vestibular nerve. In addition to the cVEMP, it is possible to record a biphasic response from the infraorbital region following stimulation that is identical to that used to record the cVEMP. This response is known as the ocular VEMP (oVEMP). The peripheral vestibular origins of the oVEMP elicited with air conduction remain controversial as some investigators argue the response originates from the saccule and others argue that the response emanates from the utricle. We review several lines of evidence and present several case studies supporting the contention that the oVEMP to air conduction stimulation derives its peripheral origins predominantly from the utricle and superior vestibular nerve. PURPOSE: To review the current evidence regarding the peripheral origins of the oVEMP. Further, a purpose of this report is to present case studies illustrating that the cVEMP and oVEMP to air conduction stimulation may vary independently of one another in patients with peripheral vestibular system impairments. RESEARCH DESIGN: A collection of case studies illustrating three common patterns of abnormality observed in patients complaining of vertigo seen in a tertiary care referral center. STUDY SAMPLE: Retrospective analysis of data from three patients complaining of dizziness and/or vertigo who have undergone vestibular function tests. RESULTS: Each case report illustrates a different pattern of abnormality of caloric, cVEMP, and oVEMP tests results from three patients with a vestibular nerve section, superior vestibular neuritis, and Ménière's disease, respectively. CONCLUSIONS: We have shown that the cVEMP and oVEMP can vary independent of one another, and in that way, provide topological information about the sites of impairment. We feel that, with caloric, oVEMP, and cVEMP tests, it is possible to augment the diagnostic information we are able to provide regarding the location, or locations, of vestibular system impairment. These findings suggest that air conduction oVEMPs measure a part of the peripheral vestibular system different from that measured by cVEMPs, perhaps the utricle, and similar to that measured by caloric testing, the superior portion of the vestibular nerve.

The Supine Superior Semicircular Canal Dehiscence Test.

Purpose The purpose of this clinical focus article is to describe a new method for assessment of superior semicircular canal dehiscence by laying the patient supine during Valsalva-induced nystagmus testing. Method The traditional Valsalva-induced nystagmus test is described, followed by a new method for assessment of superior semicircular dehiscence conducted by laying the patient supine during testing. A case study is presented to illustrate this new testing technique known as the Supine Superior Semicircular Canal Dehiscence Test. Results It is hypothesized that during Valsalva-induced nystagmus testing performed in the upright, seated position, the dura mater could potentially seal the superior semicircular canal fistula, thereby concealing a defect in the bony labyrinth and yielding a false-negative test. To circumvent this, the patient should be placed in the supine position during Valsalva-induced nystagmus testing in order to prevent the dura mater from inadvertently sealing itself against the petrous portion of the temporal bone. The Supine Superior Semicircular Canal Dehiscence Test may reveal the defect in the bony labyrinth and improve the sensitivity of the Valsalva-induced nystagmus test. Conclusions The Supine Superior Semicircular Canal Dehiscence Test may be more sensitive for identifying superior semicircular canal dehiscence in patients with traditional symptoms and a negative Valsalva-induced nystagmus test in the seated position. While a case study is presented to illustrate the potential benefits of including the Supine Superior Semicircular Canal Dehiscence Test in the battery of diagnostic tests, further research is needed in larger samples.

Vestibular Evoked Myogenic Potentials and Postural Control in Adults with Age-Related Hearing Loss.

BACKGROUND: Age-related changes to auditory function have been attributed to, through histopathological study, specific degradation of the sensory, supporting, and afferent structures of the cochlea. Similar to age-related hearing loss (ARHL), age-related changes to the vestibular sensory and supporting structures with specific degeneration of the saccule, utricle, otoconia, primary vestibular afferents have also been noted. Significant decreases in postural control with age are also well-documented in the literature attributed to multifactorial changes in function. PURPOSE: The purpose of this study is to further evaluate the association of ARHL and saccule/utricle function as measured by VEMPs and postural control measures. STUDY SAMPLE: Audiologic, vestibular and postural control results from 34 participants were analyzed. The age range was from 50 to 70 years old with 16 males and 18 females. Group 1 consisted of 33 ears from participants age 50-70 with normal hearing with average age of 60.8 years (sd 6.287 years) and an average speech-frequency PTA of 14.8 dB HL. Group 2 consisted of 27 ears from participants age 50-70 years with ARHL and an average age of 62.9 years (sd 4.984 years) with an average speech-frequency PTA of 39.9 dB HL. DATA COLLECTION AND ANALYSIS: Independent samples t-tests were used to assess group mean differences for dependent variables. The independent variable was group with 2 levels (normal hearing, ARHL). The dependent variables were cVEMP P1/N1 Amplitude, cVEMP P1 Latency, cVEMP N1 Latency, cVEMP P2 Latency, oVEMP N1/P1 Amplitude, oVEMP N1 Latency, and oVEMP P1 Latency. Additional analyses were completed using Pearson correlation to evaluate the relationship of audiometric findings to the dependent variables. RESULTS: Results indicated significantly decreased cVEMP P1/N1 amplitude and oVEMP N1/P1 amplitude adults 50-70-years of age with ARHL compared with their normal counterparts. Significant correlations were also found for audiometric results and both cVEMP and oVEMP measures. CONCLUSIONS: Overall, the results of this study describe concomitant auditory and vestibular degeneration as measured by audiometric testing and vestibular function testing involving the saccule and to a lesser degree the utricle.

A Comparison of Dizziness Handicap Inventory Scores by Categories of Vestibular Diagnoses.

OBJECTIVE: The Dizziness Handicap Inventory (DHI) is a 25-item self-report quantifying dizziness-related physical and emotional symptoms and restrictions in daily activities. DHI scores do not correlate with severity of structural vestibular deficits; thus, high DHI scores may reflect other causes of morbidity. This study investigated the relationship between total DHI scores and the presence of structural, functional, and psychiatric disorders in tertiary neurotology patients. STUDY DESIGN: Retrospective. SETTING: Tertiary center. PATIENTS: Eighty-five patients who underwent multidisciplinary neurotologic evaluations. INTERVENTION: Diagnostic. MAIN OUTCOME MEASURE(S): Active illnesses identified by a multidisciplinary neurotology team were abstracted from medical records, cataloged as structural, functional, or psychiatric disorders, and used to group patients into diagnostic categories: structural (structural disorders only), functional (functional disorders with/without structural disorders), and psychiatric (psychiatric disorders with/without other conditions). DHI scores were compared across diagnostic categories. Sensitivities and specificities of DHI scores for identifying structural versus functional or psychiatric disorders were calculated. RESULTS: Mean DHI scores differed significantly by diagnostic category (structural 35 ±â€Š18, functional 64 ±â€Š15, and psychiatric 65 ±â€Š19), before and after adjusting for age and sex (p < 0.001, Hedges' g>1.62 for structural versus functional and psychiatric categories). DHI≤30 (mild handicap) had specificity = 0.98 for structural disorders alone, whereas DHI>60 (severe handicap) had specificity = 0.88 for functional or psychiatric disorders. CONCLUSIONS: In this tertiary cohort, categories of illnesses had large effects on total DHI scores. Patients with scores ≤30 were likely to have structural disorders alone, whereas those with scores >60 were likely to have functional or psychiatric disorders, with or without coexisting structural conditions.

Agreement between the Skull Vibration-Induced Nystagmus Test and Semicircular Canal and Otolith Asymmetry.

BACKGROUND: How significant asymmetries in otolith organ function in the presence of symmetrical and asymmetrical semicircular canal function influence skull vibration-induced nystagmus testing (SVINT) has not been well described. PURPOSE: The aim of the study is to examine the agreement between SVINT and caloric testing, ocular vestibular-evoked myogenic potentials (oVEMP), and cervical vestibular-evoked myogenic potentials (cVEMP) for detecting asymmetric vestibular function. RESEARCH DESIGN: This is a retrospective study of patients presenting with the chief complaint of vertigo, dizziness, or imbalance. STUDY SAMPLE: A total of 812 patients were studied with a median age at testing of 59 years (interquartile range 46-70; range 18-93) and included 475 (59%) women. INTERVENTION: Either the monothermal warm caloric test or alternate binaural bithermal caloric test, oVEMP, and cVEMP tests were administered to all patients. All patients underwent the SVINT prior to vestibular laboratory testing. DATA COLLECTION AND ANALYSIS: Agreement between tests categorized as normal versus abnormal was summarized using percent concordance (PC). Sensitivity and specificity values were calculated for SVINT compared with other tests of vestibular function. RESULTS: There was higher agreement between ipsilateral and contralateral SVINT with the caloric test (PC = 80% and 81%, respectively) compared with oVEMP (PC = 63% and 64%, respectively) and cVEMP (PC = 76% and 78%, respectively). Ipsilateral and contralateral SVINT showed higher sensitivity for the caloric test (sensitivity = 47% and 36%, respectively) compared with oVEMP (sensitivity = 26% and 21%, respectively), or cVEMP (sensitivity = 33% vs. 27%, respectively). Specificity of SVINT was high (>80%) for all assessments of vestibular function. CONCLUSION: The presence of SVIN is a useful indicator of the asymmetry of vestibular function between the two ears when making judgments about semicircular canal asymmetry but is less sensitive to asymmetries in otolith organ function.