Effects of Age on the Frequency Amplitude Ratio of Cervical and Ocular Vestibular Evoked Myogenic Potentials.

PURPOSE: An increase in the 1000/500 Hz frequency amplitude ratio (FAR) of the cervical and ocular vestibular evoked myogenic potentials (cVEMP and oVEMP, respectively) may serve as a potential biomarker for diagnosing Meniere's disease (MD). However, the aging process can also result in an increased FAR for VEMPs. In older patients, distinguishing whether changes in VEMP FAR are due to MD or aging processes becomes difficult. We aimed to investigate the effects of age on VEMP FARs and establish a FAR-normative range for different age groups. METHOD: cVEMP and oVEMP were recorded from a total of 106 participants grouped as young, middle-aged, and older adults using air-conducted tone bursts at 500, 750, and 1000 Hz at 125 dB pSPL. The FAR was calculated for the cVEMP and oVEMP for the following frequencies: FAR1 = 1000/500, FAR2 = 1000/750, and FAR3 = 750/500. RESULTS: A significant age-related effect was observed on the cVEMP FAR. Although the oVEMP FAR showed an increasing trend with age, it was not statistically significant. Age-based normative FAR values are provided. CONCLUSIONS: Drawing from the normative FAR from this study, there is evidence that the existing MD diagnostic criteria would misidentify a considerable number of older adults. Therefore, to reduce false positives, we recommend a more stringent cVEMP and oVEMP FAR criterion in older adults.

Effects of Age and Middle Ear on the Frequency Tuning of the cVEMP and oVEMP.

BACKGROUND: Upward shift in the air conducted (AC) frequency tuning of vestibular evoked myogenic potentials (VEMPs) as an effect of aging is hypothesized to be due to the microstructural stiffening changes in the inner ear. However, with an AC stimulus, it may be possible that the shift in the frequency tuning of VEMPs as an effect of aging may also be due to contributions from the middle ear. PURPOSE: The main aim of this study was to examine the effects of age on the frequency tuning of the cervical VEMP (cVEMP) and ocular VEMP (oVEMP) and determine the role of middle ear transmission characteristics in shaping these effects. RESEARCH DESIGN: Standard group comparison. STUDY SAMPLE: One-hundred seven participants divided in three groups: young adult, middle-age, and older adults with "normal" middle ear and negative history of neurological or vestibular complaints. DATA COLLECTION AND ANALYSES: Middle ear measures included static admittance and middle ear resonant frequency. cVEMP and oVEMPs were elicited with AC tone bursts at 500, 750, and 1,000 Hz. RESULTS: No significant effect of age was observed on any of the middle ear measures. There was a significant effect of age on the amplitude of the cVEMP, but this effect was frequency specific. The age-related reduction in cVEMP corrected amplitude was only observed when the eliciting stimulus was 500 or 750 Hz, with no significant effect observed with a 1,000 Hz stimulus. For the oVEMP, the effects of age were apparent at all stimulus frequencies. We also observed a general upward shift in the frequency tuning of both the cVEMP and oVEMP for middle-age and older adults, with 750 and 1,000 Hz yielding higher response rates and larger amplitudes among middle-aged and older adults. Measurements of middle ear did not significantly contribute to the observed findings. CONCLUSIONS: The upward shift in frequency tuning of VEMPs among middle age and older adults could be due to the changes in the vestibular system and not from the middle ear. These results support the use of different frequency stimuli (i.e., 750 or 1,000 Hz) to elicit a VEMP if a response is absent using a 500 Hz stimulus, especially in patients over the age of 40.

Inter-trial coherence as a measure of synchrony in cervical vestibular evoked myogenic potentials.

BACKGROUND: Cervical vestibular evoked myogenic potentials (cVEMPs) are surface-recorded responses that reflect saccular function. Analysis of cVEMPs has focused, nearly exclusively, on time-domain waveform measurements such as amplitude and latency of response peaks, but synchrony-based measures have not been previously reported. NEW METHOD: Time-frequency analyses were used to apply an objective response-detection algorithm and to quantify response synchrony. These methods are new to VEMP literature and have been adapted from previous auditory research. Air-conducted cVEMPs were elicited using a 500 Hz tone burst in twenty young, healthy participants. RESULTS: Time-frequency characteristics of cVEMPs and time-frequency boundaries for response energy were established. An inter-trial coherence analysis approach revealed highly synchronous responses with representative inter-trial coherence values of approximately 0.7. COMPARISON WITH EXISTING METHODS: Inter-trial coherence measures were highly correlated with conventional amplitude measures in this group of young, healthy adults (R2 = 0.91 - 0.94), although the frequencies at which these measures had their largest magnitude were unrelated (R2 =.02). Conventional measures of peak-to-peak amplitude and latency were consistent with previous literature. Interaural asymmetry ratios were comparable between amplitude- and synchrony-based measures. CONCLUSIONS: Synchrony-based time-frequency analyses were successfully applied to cVEMP data and this type of analysis may be helpful to differentiate synchrony from amplitude in populations with disrupted neural synchrony.

Temporal Modulation Transfer Functions of Amplitude-Modulated Cervical Vestibular-Evoked Myogenic Potentials in Young Adults.

OBJECTIVES: Cervical vestibular-evoked myogenic potentials (cVEMPs) are widely used to evaluate saccular function in clinical and research applications. Typically, transient tonebursts are used to elicit cVEMPs. In this study, we used bone-conducted amplitude-modulated (AM) tones to elicit AMcVEMPs. This new approach allows the examination of phase-locked vestibular responses across a range of modulation frequencies. Currently, cVEMP temporal modulation transfer functions (TMTFs) are not well defined. The purposes of the present study were (1) to characterize the AMcVEMP TMTF in young, healthy individuals, (2) to compare AMcVEMP TMTFs across different analysis approaches, and (3) to determine the upper frequency limit of the AMcVEMP TMTF. DESIGN: Young adults (ages 21 to 25) with no history of vestibular lesions or middle ear pathologies participated in this study. Stimuli were amplitude-modulated tones with a carrier frequency of 500 Hz and modulation frequencies ranging from 7 to 403 Hz. Stimuli were presented at 65 dB HL via a B81 bone-oscillator. RESULTS: AMcVEMP waveforms consisted of transient onset responses, steady-state responses, and transient offset responses; the behavior of these different types of responses varied with modulation frequency. Differences in the TMTF shape were noted across different measures. The amplitude TMTF had a sharp peak, while signal-to-noise ratio and phase coherence TMTFs had broader shapes with plateaus across a range of modulation frequencies. Amplitude was maximal at modulation frequencies of 29 and 37 Hz. Signal-to-noise ratio maintained its peak value at modulation frequencies between 17 Hz and 127 Hz. Phase coherence and modulation gain maintained their peak values at modulation frequencies between 17 Hz and 143 Hz. CONCLUSIONS: AMcVEMPs reflect transient onset and offset responses, as well as a sustained response with the periodicity of an amplitude-modulation frequency. AMcVEMP TMTFs had variable shapes depending on the analysis being applied to the response; amplitude had a narrow shape while others were broader. Average upper frequency limits of the AMcVEMP TMTF were as high as approximately 300 Hz in young, healthy adults.

Agreement Between Caloric and Horizontal Video Head Impulse Testing in School-Aged Children Presenting With Dizziness.

OBJECTIVE: The purpose of this investigation was to determine the relationship between the horizontal semicircular canal video head impulse test (hvHIT) and the caloric test in a sample of school-age children evaluated due to complaints of dizziness or imbalance. In adults, these two tests provide different but complementary information regarding vestibular function and/or pathology. However, the most common causes of vestibular loss in children are different than those in adults, and it is not clear how these two tests of horizontal semicircular canal function are related in a pediatric population. METHOD: This is a retrospective study of electronic records of pediatric patients (< 18 years old) who were referred for vestibular function testing and completed both hvHIT and caloric testing. Agreement between both test results was evaluated by examining measures of sensitivity, specificity, and calculating Cohen's kappa. RESULTS: Results from 117 patients (mean age = 13.7 years, age range: 8-17 years, 37 males) were analyzed. Most patients (97/115 [84.3%]) demonstrated both normal hvHIT and caloric test results. Compared to caloric testing, the hvHIT had poor sensitivity (38.9%) and excellent specificity (98.0%). Cohen's kappa analysis revealed moderate agreement between the methods (coefficient = 0.49 [0.24, 0.73]). Where disagreement between the two tests occurred, the final diagnosis was not contingent on either test result. CONCLUSIONS: There is a moderate agreement between the hvHIT and the caloric test in pediatric patients presenting to a tertiary care medical center for a vestibular evaluation. Most patients in this cohort presented with normal findings. The specificity of hvHIT was excellent, although the sensitivity was low. This may be related to the low prevalence of peripheral vestibular system disease in this study cohort, and these results do not generalize to centers that serve populations of children where vestibular disorders are more prevalent (e.g., children with sensorineural hearing loss).

Nonlinearity in bone-conducted amplitude-modulated cervical vestibular-evoked myogenic potentials: harmonic distortion products.

Otolith organs of the balance system, the saccule and utricle, encode linear acceleration. Integrity of the saccule is commonly assessed using cervical vestibular-evoked myogenic potentials (cVEMPs) arising from an inhibitory reflex along the vestibulospinal pathway. Conventional approaches to eliciting these responses use brief, transient sounds to elicit onset responses. Here we used long-duration amplitude-modulated (AM) tones to elicit cVEMPs (AMcVEMPs) and analyzed their spectral content for evidence of nonlinear processing consistent with known characteristics of vestibular hair cells. Twelve young adults (ages 21-25) with no hearing or vestibular pathologies participated in this study. AMcVEMPs were elicited by bone-conducted AM tones with a 500-Hz carrier frequency. Eighteen modulation frequencies were used between 7 and 403 Hz. All participants had robust distortion products at harmonics of the modulation frequency. Total harmonic distortion ranged from approximately 10 to 80%. AMcVEMPs contain harmonic distortion products consistent with vestibular hair cell nonlinearities, and this new approach to studying the otolith organs may provide a noninvasive, in vivo method to study nonlinearity of vestibular hair cells in humans.NEW & NOTEWORTHY The otolith balance organs of humans are assessed for basic science and clinical applications by using vestibular-evoked myogenic potentials (VEMPs). Traditionally, VEMPs are elicited with brief, transient sounds to study onset responses. We used long-duration sounds to elicit steady-state VEMPs. This allowed us to measure nonlinear distortion products, consistent with nonlinear processing in vestibular hair cells. This new approach may help to better understand links between otolith organs and balance function.

Comparison of Bone-Conducted Cervical VEMPs Elicited by B71 and B81 Bone Vibrators.

OBJECTIVE: A variety of stimulus delivery methods can elicit vestibular evoked myogenic potentials (VEMPs). The current study compared bone conduction (BC) cervical VEMPs (cVEMPs) across two different clinical bone vibrators. It was hypothesized that the B81 transducer would be more effective for producing larger BC-cVEMP peak to peak amplitudes due to its low-frequency advantages in pure-tone audiometry applications. DESIGN: Twenty young adults under the age of 40 years with no reported history of hearing or balance disorders participated in the study. BC cVEMPs were elicited using two clinical bone transducers: the Radioear B71 bone vibrator and the Radioear B81 bone vibrator. Both transducers were calibrated using the acoustic method of calibration before data collection, and the linear dynamic range of the transducers was determined. Participants were asked to sit and match a fixed electromyography (EMG) target level of 100 µV, while BC cVEMPs were recorded using stimulus frequencies of 250, 500, and 750 Hz. RESULTS: Statistically significant differences in raw amplitude at 250 and 750 Hz between the B71 and B81 were observed; the B71 produced larger peak to peak amplitudes over the B81. At 500 Hz, larger amplitudes were observed with the B71, but results were not statistically significant. The B71 produced significantly lower cVEMP thresholds at all three frequencies. Across both transducers, 500 Hz produced the largest peak to peak amplitude compared with 250 and 750 Hz. Peak to peak amplitude did not increase above 55 dB nHL for 250 and 500 Hz, but amplitude continued to increase at 750 Hz. DISCUSSION: The present study found statistically significant differences in BC-cVEMP amplitude and threshold between the B71 and B81, but results were not what we hypothesized. In general, the B71 elicited larger BC-cVEMP amplitudes and lower thresholds compared with the B81. Additionally, 500 Hz was found to be the best frequency for both BC transducers, contrasting previous studies suggesting lower frequencies yield larger BC-cVEMP amplitudes. It is possible that these average differences could also be clinically significant when looking at individual amplitude differences. Larger peak to peak amplitudes at 500 Hz may be partially due to the underlying physical levels used in the current study, as well as the output spectra of the transducers, and may explain the larger response amplitudes observed at 500 Hz compared with 250 Hz.

Effects of Stimulus Polarity on Amplitude-Modulated Cervical Vestibular-Evoked Myogenic Potentials.

BACKGROUND: Traditional approaches to cervical vestibular-evoked myogenic potentials use a transient stimulus to elicit an onset response. However, alternate approaches with long duration stimuli may allow the development of new methodologies to better understand basic function of the vestibular system, as well as potentially developing new clinical applications. PURPOSE: The objective of this study was to examine the effects of stimulus polarity on response properties of amplitude-modulated cervical vestibular-evoked myogenic potentials (AMcVEMPs). RESEARCH DESIGN: Prospective, repeated-measures, within-subjects design. STUDY SAMPLE: Participants were 16 young, healthy adults (ages 21-38 years). DATA COLLECTION AND ANALYSIS: Amplitude-modulated tones, with carrier frequency of 500 Hz and modulation frequency of 37 Hz, were used to elicit AMcVEMPs. Responses were analyzed in three different stimulus polarity conditions: condensation, rarefaction, and alternating. The resulting data were analyzed for differences across polarity conditions. RESULTS: AMcVEMP amplitudes, both raw and corrected for tonic muscle activation, were equivalent across the different stimulus phase conditions. In addition, response signal-to-noise ratio and phase coherence were equivalent across the different phases of the stimulus. CONCLUSION: Analyses of AMcVEMPs are stable when the carrier frequency starting phase is altered and the phase of the temporal envelope is constant.

Test-Retest Reliability of the Dizziness Symptom Profile.

OBJECTIVES: This investigation was conducted to measure the test-retest reliability of the Dizziness Symptom Profile (DSP). The DSP was developed to assist primary care providers, general otolaryngologists, and other health care providers in the development of a differential diagnosis for patients who present with dizziness, vertigo, or unsteadiness. The DSP yields a score ranging from 0 to 100% for each of 7 subscales. Each subscale represents a different diagnosis including benign paroxysmal positional vertigo, Ménière's disease, persistent postural-perceptual dizziness (PPPD), superior semi-circular canal dehiscence, vestibular migraine, vestibular neuritis, and general unsteadiness. DESIGN: Subjects were 150 adult patients (mean age 56.79 years, SD 15.69 years) referred to the Balance Disorders Clinic at Vanderbilt University Medical Center. Subjects completed two administrations of the DSP. The mean interval between test administrations was 1.58 days (SD 1.78 days). The response modes for the DSP were both a 0 to 100 mm visual analog scale (scored 0 mm = "strongly disagree" to 100 mm = "strongly agree") and, by extrapolation, the original 5-point Likert scale where the anchors were "strongly disagree" (scored 0 points) and "strongly agree" (scored 4 points). RESULTS: Pearson correlation coefficients were calculated to assess test-retest reliability for individual DSP items, and ranged from r = 0.67 to 0.91 (mean 0.80; p < 0.001). Cronbach's α coefficients were calculated to assess internal consistency reliability of items comprising the seven subscales. Each subscale had an acceptable level of internal consistency (Cronbach's α coefficients > 0.7) with the exception of PPPD which approached 0.7. Intraclass correlation coefficient estimates and their 95% confidence intervals were also calculated to assess the relative reliability of the subscales. All 7 subscales showed moderate to strong test-retest reliability, with intraclass correlation coefficients ranging from 0.85 to 0.94. Minimal detectable change (MDC) scores were calculated to assess absolute variability/measurement error for the seven subscale scores (which range from 0 to 100%). MDC values ranged from 16% (PPPD) to 25% (unsteadiness). CONCLUSIONS: (1) The test-retest reliability of the DSP is moderate to strong. (2) MDC values for each subscale were determined. (3) The DSP coupled with the Dizziness Handicap Inventory enables the clinician to evaluate the constructs of dizziness impairment, and disability/handicap. (4) The DSP may help provide a window to the natural history of dizziness disease(s). (5) The DSP provides a less biased assessment of the symptoms reported by the patient.

Effects of Tonic Muscle Activation on Amplitude-Modulated Cervical Vestibular Evoked Myogenic Potentials (AMcVEMPs) in Young Females: Preliminary Findings.

Cervical vestibular evoked myogenic potentials (cVEMPs) are usually elicited by transient tonebursts, but when elicited by amplitude-modulated (AM) tones, they can provide new information about cVEMPs. Previous reports of cVEMPs elicited by AM tones, or AMcVEMPs, have not systematically examined the effects of tonic EMG activation on their response properties. Fourteen young, healthy female adults (ages 20-24) with clinically normal audiograms participated in this study. AMcVEMPs were elicited with bone-conducted 500 Hz tones amplitude modulated at a rate of 37 Hz and recorded for five different EMG targets ranging from 0 to 90 µV. Amplitude increased linearly as tonic EMG activation increased. Signal-to-noise ratio (SNR) was minimal at 0 µV, but robust and with equivalent values from 30 to 90 µV; phase coherence and EMG-corrected amplitude had findings similar to SNR across EMG target levels. Interaural asymmetry ratios for SNR and phase coherence were substantially lower than those for raw or corrected amplitude. AMcVEMP amplitude scaled with tonic EMG activation similar to transient cVEMPs. Signal-to-noise ratio, phase coherence, and EMG-corrected amplitude plateaued across a range of EMG values, suggesting that these properties of the response reach their maximum values at relatively low levels of EMG activation and that higher levels of EMG activation are not necessary to record robust AMcVEMPs.

Vestibular function after cochlear implantation: A test battery and case-by-case approach.

OBJECTIVES: The purpose of this study was to assess the effects of cochlear implantation on the functional integrity of the horizontal semicircular canal using multiple methodologies, and to discuss and highlight the limitations of using isolated vestibular tests to assess vestibular function in surgical ears. METHODS: Ten cochlear implant patients were consented to undergo a preoperative and 3-month postoperative vestibular assessment. The horizontal semicircular canal (SCC) was assessed using three different vestibular test measures that assess function using different stimuli and at different frequencies ranges: caloric testing, sinusoidal harmonic acceleration testing in the rotary chair, and video head impulse testing in the plane of the horizontal SCC. Data was analyzed using different methods: descriptive, statistical, and by an examination of individual case studies. RESULTS: Each analysis method yielded a different interpretation. Statistical analysis showed no significant group mean differences between baseline pre-op vestibular test results and 3-month post-op vestibular test results. Descriptive analysis showed 30% of individuals presented with postoperative abnormal vestibular testing findings. A case study examination showed that only one patient presented with a post-op decrease in vestibular function in the implanted ear. CONCLUSIONS: There are several limitations of conventional vestibular testing in postsurgical cochlear implant patients. A test-battery approach, including case history, and test interpretation made on a case-by-case basis is needed to determine whether the patient has undergone vestibular damage, is at risk for falling, or in need of further management. LEVEL OF EVIDENCE: 2b individual cohort study.

A factor analytic assessment of the English translation of the neuropsychological vertigo inventory (NVI).

PURPOSE: Vestibular impairments have been associated with a variety of cognitive deficits, most notably deficits in visuo-spatial memory. The Neuropsychological Vertigo Inventory (NVI) was developed to measure self-reported cognitive deficits in patients with dizziness and/or vertigo. The original French language version of the NVI includes 28 items and 7 subscales. The purpose of the present investigation was to determine whether the statistical assessment of an English language version supported the presence of the same cognitive constructs as the French version of the NVI. METHOD: The English language adaptation of the NVI (referred to here as the NVIe) was administered to an unselected sample of 280 patients that were being evaluated for dizziness and/or vertigo in a tertiary care dizziness clinic. The individual item scores from the NVIe were subjected to an exploratory factor analysis (EFA). RESULTS: The results of the data analysis supported a 22-item NVIe consisting of 4 constructs: affective state, temporal memory, spatial memory, visual spatial cognition. CONCLUSIONS: The NVIe is a new tool for screening cognitive constructs that may be affected by vestibular impairments. Prior to clinical implementation of the NVIe, additional studies of reliability and convergent validity are needed.

The Clinical Significance of the Failure to Perceive Vertigo in the Postcaloric Period Despite a Robust Caloric Response.

Purpose The purpose of this project was to explore the association between the perception of motion during caloric testing and two tasks associated with central vestibular processing: postural stability and visuospatial memory. Method This was a prospective study of 25 patients who were found to have nonvestibular etiologies of their symptoms and normal vestibular function test results and who underwent caloric testing with a mean maximum slow phase eye velocity for each irrigation of 15° or greater. Following each caloric irrigation, patients were asked whether they had any sensation of movement. Patients were grouped based on the presence or absence of motion during the caloric exam (motion perception vs. absent perception). Postural stability was assessed using computerized dynamic posturography, and visuospatial memory was assessed using a memory match card game application. Results There were no significant differences between groups on any measures of peripheral vestibular function. However, the Absent Perception Group showed greater postural instability during Condition 5 of posturography and performed significantly worse on a task of visuospatial working memory. Both age and absence of motion perception predicted abnormal performance on measures of postural stability and visuospatial working memory. Conclusions There appears to be clinical implications to a lack of motion perception during the caloric exam in patients with an otherwise normal peripheral vestibular system. Based on the current findings, we are unable to determine whether differences in postural stability and visuospatial memory were due to age or a central vestibular processing deficit.

Maximum Output and Low-Frequency Limitations of B71 and B81 Clinical Bone Vibrators: Implications for Vestibular Evoked Potentials.

OBJECTIVES: Bone-conducted vestibular evoked myogenic potentials (VEMPs) are tuned to have their maximum amplitude in response to tone bursts at or below 250 Hz. The low-frequency limitations of clinical bone vibrators have not been established for transient, tone burst stimuli at frequencies that are optimal for eliciting VEMPs. DESIGN: Tone bursts with frequencies of 250 to 2000 Hz were delivered to B71 and B81 bone vibrators and their output was examined using an artificial mastoid. The lower-frequency limit of the transducers was evaluated by examining the spectral output of the bone vibrators. Maximum output levels were evaluated by measuring input-output functions across a range of stimulus levels. RESULTS: Both the B71 and B81 could produce transient tone bursts with frequency as low as 400 Hz. However, tone bursts with frequencies of 250 and 315 Hz resulted in output with peak spectral energy at approximately 400 Hz. From 500 to 2000 Hz, maximum output levels within the linear range were between 120 and 128 dB peak force level. The newer B81 bone vibrator had a maximum output approximately 5 dB higher than the B71 at several frequencies. CONCLUSIONS: These findings demonstrate that both transducers can reach levels appropriate to elicit bone-conducted VEMPs, but the low-frequency limitations of these clinical bone vibrators limit tone burst frequency to approximately 400 Hz when attempting to stimulate the otolith organs via tone bursts.

Diabetes and the Vestibular System.

Falls are among the most injurious, costly, and feared conditions affecting older adults. Patients with diabetes have a significantly greater risk for falling due to complications affecting the sensory systems required for balance: vision, proprioception, and vestibular. The effects of diabetes mellitus on the vestibular system are perhaps the least understood of these systems. The vestibular system is complex, includes multiple structures, and is difficult and expensive to thoroughly assess. There is pathophysiologic evidence suggesting a direct effect of diabetes mellitus complications on the vestibular system, but there is limited clinical evidence regarding which specific vestibular structures are most adversely affected. Nevertheless, large population-based studies show that patients with diabetes are more likely to have vestibular loss, have a high prevalence of a specific vestibular disorder called benign paroxysmal positional vertigo, and are at a greater risk for falling. Based on the available evidence, a balance screening and an evaluation of benign paroxysmal positional vertigo, a common but easy to treat pathology, in patients with diabetes is recommended as well as counseling on falls risk and home modifications.

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.

The Medial Canthus Reference Electrode Is not Electrically Indifferent to the Ocular Vestibular Evoked Myogenic Potential.

OBJECTIVE: To determine whether a reference electrode placed over the contralateral medical canthus is electrically indifferent to the ocular vestibular evoked myogenic potential (oVEMP). STUDY DESIGN: Prospective observational study. SETTING: Tertiary academic center. PARTICIPANTS: Nineteen otologically normal subjects. METHODS: oVEMPs were recorded using a 500 Hz tone burst at 125 dB pSPL using both a conventional dual infra-orbital derivation and contralateral infraorbital electrode referenced to a medial canthus electrode known as the "belly-tendon" derivation. RESULTS: The belly-tendon derivation produced significantly larger oVEMP amplitudes. This appears to be due to a polarity inversion of the first negative peak that occurs when the reference electrode is placed over the medial canthus. Thus, the belly-tendon derivation was associated with reference contamination, but in this instance the reference contamination produced an augmented oVEMP amplitude. CONCLUSIONS: Neither the dual infra-orbital nor belly-tendon electrode montages are electrically neutral. Reference contamination is the source of both a decrease in amplitude using conventional recording techniques and increased amplitude using the belly-tendon montage. The results support the contention that the belly-tendon montage generates a reversed polarity response, i.e., algebraically subtracted (i.e., added in the differential amplifier) from the response recorded at the infraorbital midline enhancing the oVEMP amplitude. It should be noted that the amplitude gained when using the belly-tendon montage may also be due to electromyographic (EMG) generated by extraocular muscles other than the inferior oblique generator, resulting in a loss of specificity. The authors recommend the belly-tendon montage be used in clinical situations where the oVEMP is absent or low in amplitude.

Age predicts the absence of caloric-induced vertigo.

INTRODUCTION: The absence of vertigo during the caloric test, despite a robust response, has been suggested to represent a central vestibular system phenomenon. The purpose of this investigation was to determine the prevalence of absent caloric-induced vertigo perception in an unselected group of patients and to assess possible predicting variables. METHODS: Prospective investigation of 92 unselected patients who underwent caloric testing. Inclusion criteria were that each patient generate a maximum slow phase velocity (maxSPV) ≥ 15 deg/sec and a caloric asymmetry of ≤10%. Following the caloric, patients were asked, "Did you have any sensation of motion?" RESULTS: Results showed 75% of patients reported motion with a mean age of 56.51 years compared to a mean age of 66.55 in the 25% of patients reporting an absence of motion. A logistic regression was performed and the overall model was statistically significant accounting for 29% of the variance in caloric perception. The significant predictor variables were patient age and maxSPV of the caloric response. The effect size for both variables was small with an odds ratio of .9 for maxSPV and 1.06 for age. CONCLUSIONS: The current investigation showed that both age and maxSPV of the caloric response were significant predictors of vertigo perception during the caloric exam. However, the association between age and caloric perception is not conclusive. Although there is evidence to suggest that these findings represent age-related changes in the central processing of vestibular system stimulation, there are additional unmeasured factors that influence the perception of caloric-induced vertigo.

Ocular and Cervical Vestibular Evoked Myogenic Potentials in Patients With Vestibular Migraine.

OBJECTIVE: To evaluate the relationship between normal and abnormal ocular vestibular evoked myogenic potentials (oVEMP) and cervical vestibular evoked myogenic potentials (cVEMP) in patients with and without vestibular migraine (VM). STUDY DESIGN: Retrospective review of oVEMP and cVEMP results in patients with vestibular disorders who were assessed clinically and completed vestibular function studies. Data were extracted from a deidentified RedCap Repository. SETTING: Tertiary care multispecialty medical center. PATIENTS: Subjects were 212 consecutive adults meeting prespecified inclusion criteria who were evaluated in the Balance Disorders Clinic at Vanderbilt University Medical Center between 2011 and 2017. Patients with bilaterally absent VEMPs were excluded from the study. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Proportions of subjects with or without VM in one of the following four test outcomes: normal cVEMP/normal oVEMP, abnormal cVEMP/abnormal oVEMP, abnormal cVEMP/normal oVEMP, and normal cVEMP/abnormal oVEMP. RESULTS: There was a significant relationship between VM and cVEMP and oVEMP test outcomes. CONCLUSION: Patients with VM are more likely than subjects with vestibular disorders other than migraine to exhibit normal cVEMP responses in the presence of unilaterally abnormal oVEMP responses. Such a VEMP pattern may be a biomarker of VM and further supports a possible pathophysiologic relationship between the utriculo-ocular reflex and VM.

Reevaluating Order Effects in the Binaural Bithermal Caloric Test.

PURPOSE: The purpose of this study was to determine whether a significant order effect exists in the binaural bithermal caloric test. METHOD: Fifteen volunteers (mean age = 24.3 years, range = 18-38 years) with no history of vestibular disorder, hearing loss, concussion, or neurological disease underwent caloric testing on 3 occasions. Irrigations were randomized using 8 possible order combinations. The parameters of interest included unilateral weakness, directional preponderance, total response from the right ear, and total response from the left ear. RESULTS: Order effects were analyzed using 2 methods. The first analysis was done looking at the 8 possible orders. We also had an a priori established hypothesis that the first irrigation tested would influence the calculation of unilateral weakness more than the other 3 irrigations. To test this hypothesis, the 8 orders were condensed into 4 order conditions based on the first irrigation. The effect of order was determined using analysis of variance tests. Although the first irrigation tended to be the largest, no significant effects were observed. CONCLUSIONS: This experiment demonstrated that while there is great inter-individual and intra-individual variability in caloric test results, the order of irrigations had no significant effect in the test. Future studies may explore the effects of nonphysiological factors on test results.