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.

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.

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.

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.

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.

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 ± 18, functional 64 ± 15, and psychiatric 65 ± 19), 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 Functional and Electrophysiologic Measures in Patients with Unilateral Peripheral Vestibular System Impairment

This investigation was conducted to determine whether there was congruence between "physiology-based" definitions of compensated and uncompensated unilateral peripheral vestibular system impairment and "functional" measures of self-perceived dizziness disability/handicap. A retrospective analysis was performed on data obtained from 122 patients evaluated in the Balance Function Laboratory at Henry Ford Hospital over a 4-year period. Both electronystagmography and rotational test data were tabulated. Additionally, results of a self-report measure of dizziness disability/handicap were tabulated. Patients were placed into four groups, with one group representing normal vestibulometric test results, one group representing compensated unilateral peripheral vestibular system impairment, and two groups representing increasing magnitudes of uncompensated unilateral peripheral vestibular system impairment. The total and subscale scores on the self-report measure served as the dependent variable. Results showed a lack of congruence between the physiologic and functional measures. We interpret these findings as evidence that factors other than semiobjective evidence of vestibular system compensation probably impact functional recovery following unilateral peripheral vestibular system impairment.

A Reexamination of the Long Latency N1 Response in Patients with Tinnitus

There have been disparate findings reported previously by investigators who have examined differences in the cortically generated N1 (i.e., N100) from control and tinnitus samples. Investigators have employed differing stimulation paradigms applied to relatively small subject samples. Accordingly, it is not surprising that there has been no unanimity in the reported findings. The present investigation was conducted to determine, once again, whether differences exist in the cortically generated N1 potential recorded from both normals and subjects with bothersome tinnitus. In this investigation both passive and selective auditory attention paradigms were employed. Subjects were a total of 63 adults (31 controls and 32 tinnitus patients). The mean score on the Tinnitus Handicap Inventory for the tinnitus group was 39 points. Results failed to reveal group differences in the latency of N1 across listening conditions. However, tinnitus patients demonstrated N1 potentials that were of significantly smaller amplitude than those obtained from normal subjects. These findings are consistent with those reported in previous investigations.

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 predominately 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.

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.

Transforming Superior Canal Dehiscence to Chronic Subjective Dizziness: From SCD to CSD

Patients presenting with chronic dizziness and no identifiable vestibular impairments have been described as having “extravestibular” symptoms, or “psychogenic dizziness.” In 2005, Staab and Ruckenstein described a syndrome they referred to as “chronic subjective dizziness” (CSD), which characterized this concept more clearly. According to Staab and Ruckenstein (2003), the primary physical symptoms of CSD are continual nonvertiginous dizziness or subjective imbalance that persists for 3 mo or longer. Patients suffering from CSD often describe their dizziness as a rocking or swaying when sitting or standing. This case study describes a 41-yr-old female who originally presented with complaints of noise-induced vertigo. The patient's history, imaging studies, and balance function examinations led to the diagnosis of a right-sided superior canal dehiscence (SCD). After surgical repair of the dehiscence, the quantitative electrophysiological tests returned to normal. However, the patient's scores on measures of anxiety, depression, and self-perceived dizziness handicap increased significantly postoperatively. This case illustrates the transformation of a peripheral end-organ impairment (i.e., SCD) into a psychiatric condition (i.e., CSD).

Pediatric Oculomotor Findings during Monocular Videonystagmography: A Developmental Study

Background: The differential diagnosis of a dizzy patient >4 yrs old is often aided by videonystagmography (VNG) testing to provide a global assessment of peripheral and central vestibular function. Although the value of a VNG evaluation is well-established, it remains unclear if the VNG test battery is as applicable to the pediatric population as it is for adults. Oculomotor testing specifically, as opposed to spontaneous, positional, and caloric testing, is dependent upon neurologic function. Thus, age and corresponding neuromaturation may have a significant effect on oculomotor findings.

Purpose: The purpose of this investigation was to describe the effect of age on various tests of oculomotor function during a monocular VNG examination. Specifically, this study systematically characterized the impact of age on saccade tracking, smooth pursuit tracking, and optokinetic (OPK) nystagmus.

Research Design: The present study used a prospective, repeated measures design.

Study Sample: A total of 62 healthy participants were evaluated. Group 1 consisted of 29 4- to 6-yr-olds. Group 2 consisted of 33 21- to 44-yr-olds. Each participant completed a standard VNG oculomotor test battery including saccades, smooth pursuit, and OPK testing in randomized order using a commercially available system.

Data Collection and Analysis: The response metrics saccade latency, accuracy, and speed, smooth pursuit gain, OPK nystagmus gain, speed and asymmetry ratios were collected and analyzed.

Results: Significant differences were noted between groups for saccade latency, smooth pursuit gain, and OPK asymmetry ratios. Saccade latency was significantly longer for the pediatric participants compared to the adult participants. Smooth pursuit gain was significantly less for the pediatric participants compared to the adult participants. The pediatric participants also demonstrated increased OPK asymmetry ratios compared to the adult participants.

Conclusions: Significant differences were noted between the pediatric and adult participants for saccade latency, smooth pursuit gain, and OPK asymmetry. Saccade latency was significantly longer for the pediatric participants compared to the adult participants. Smooth pursuit gain was significantly less for the pediatric participants compared to the adult participants. The pediatric participants also demonstrated increased OPK asymmetry compared to the adult participants. Caution should be exercised when comparing pediatric test results to adult normative values to avoid “false positive” diagnoses of central vestibular involvement.

Psychological Comorbidities and Their Relationship to Self-Reported Handicap in Samples of Dizzy Patients

Factors such as anxiety, depression, somatic awareness, autonomic symptoms, and differences in coping strategies are known to affect dizziness handicap. We studied these factors in 63 consecutive "dizzy" patients. This sample was subgrouped into normals and patients with benign paroxysmal positional vertigo, compensated and uncompensated unilateral peripheral vestibular system impairment, or abnormal vestibular evoked myogenic potential as a single significant diagnostic finding. Results showed that (1) anxiety and depression occur with greater frequency in dizzy patients than in the normal population; (2) the magnitude of anxiety, depression, somatization, and autonomic symptoms does not differ significantly in subgroups of patients; (3) women tended to report greater handicap and somatic/autonomic symptoms; and (4) Dizziness Handicap Inventory total scores were correlated with patients' complaints of somatic/autonomic symptoms, anxiety, depression, and coping strategies. These findings suggest that self-reported measures represent unique pieces of information important for the management of dizzy patients. Factores tales como la ansiedad, la depresión, la conciencia somática, los síntomas autonómicos y las diferencias en las estrategias de afrontamiento, se sabe que afectan el impedimento por mareo. Estudiamos estos factores en 63 pacientes “mareados” consecutivos. Esta muestra fue sub-agrupada en pacientes normales, con vértigo posicional paroxístico benigno, con trastornos periféricos unilaterales, compensados y descompensados, del sistema vestibular, o con potenciales miogénicos vestibulares evocados anormales, como único hallazgo diagnóstico significativo. Los resultados mostraron que (1) la ansiedad y la depresión ocurrían con mayor frecuencia en pacientes mareados que en la población normal; (2) la magnitud de la ansiedad, la depresión, la somatización y los síntomas autonómicos no difería significativamente entre los sub-grupos de pacientes; (3) las mujeres tendieron a reportar un impedimento mayor y mayores síntomas somáticos/autonómicos; y (4) los puntajes totales del Inventario de Impedimento por Mareo correlacionaron con los quejas de los pacientes de síntomas somáticos/autonómicos, ansiedad, depresión, y estrategias de afrontamiento. Estos hallazgos sugieren que las mediciones auto-reportadas representan piezas singulares de información importante para el manejo de los pacientes mareados.

Amplitude Normalization Reduces Cervical Vestibular Evoked Myogenic Potential (cVEMP) Amplitude Asymmetries in Normal Subjects: Proof of Concept

Background: The cervical vestibular evoked myogenic potential (cVEMP) is an acoustically synchronized, signal averaged, brief inhibitory response of a contracted muscle usually resulting from an acoustic stimulus. The cVEMP is recorded from the tonically contracted sternocleidomastoid muscle (SCM). The presence and amplitude of the cVEMP is related to both the integrity of the sacculo-collic pathway and magnitude of electromyographic (EMG) activity at the time of recording. Measurement variables include the absolute latency of the primary positive going component (referred to as P13) and interaural (i.e., left versus right) latency differences. Also measured is the peak-to-peak interaural amplitude asymmetry (IAA; percent difference in amplitude, left versus right). It is known that the amplitude of the cVEMP is positively correlated with the magnitude of tonic EMG from which the evoked potential is extracted. Thus, if EMG amplitude is uncontrolled, one cannot determine whether cVEMP asymmetries are occurring due to unilateral end organ disease or asymmetric tonic EMG activity. Two methods have been suggested to control for tonic EMG activity. These include (1) patient self-monitoring of EMG activity with biofeedback and (2) mathematical correction (i.e., amplitude normalization) of the left and right cVEMP waveforms. Currently, it is unknown how effective amplitude normalization techniques are at reducing cVEMP amplitude asymmetry in the presence of varying levels of EMG.

Purpose: The purpose of this investigation was to determine whether the use of amplitude correction techniques would reduce significantly the P13-N23 IAA data in otologically and neurologically intact adults when the level of EMG was varied between right and left sides.

Research Design: A prospective, repeated measures design was used for three different investigations in which cVEMPs were recorded and then processed using amplitude correction.

Study Sample: Subjects were 20 otologically and neurologically health young adults between 21 and 29 yr of age.

Intervention: cVEMPs were recorded at four different EMG target levels ranging from 100 to 400 μV. The absolute peak-to-peak amplitude of P13-N23, absolute latency of P13, and the left/right amplitude asymmetry of P13-N23 were measured both with and without the use of EMG amplitude correction techniques. IAAs were calculated using 10 different conditions of varying EMG asymmetry with and without amplitude correction. Data Collection and Analysis: Data were analyzed using repeated measures analysis of variance (ANOVA) to detect tonic EMG level-dependent differences separately for P13 latency, P13-N23 peak-to-peak amplitude, and mean root mean square (RMS) amplitude cVEMP responses. The amplitude of cVEMP responses from the left and right side were used to calculate IAA for subsequent analyses. Linear regression analyses compared level of tonic EMG with cVEMP amplitude. A one-way multivariate analysis of variance (MANOVA) was used to determine if IAAs were significantly reduced following amplitude correction. Any differences found were investigated using unplanned linear contrasts.

Results: The uncorrected cVEMP amplitude and RMS EMG all increased significantly with increases in the EMG target levels. With amplitude correction, cVEMP amplitude did not change significantly with changes in RMS EMG or EMG target levels.

Conclusions: These findings suggest that the use of amplitude correction techniques represent an effective method of neutralizing the factor of variability in tonic EMG level on the cVEMP that would be otherwise uncontrolled. Indeed when correction is employed in cases of extreme tonic EMG asymmetry, the upper limit of percent IAA is roughly half of that when EMG correction techniques are not used. Our findings are also in agreement with those of Bogle et al (2013) showing that the input/output growth function for P13/N23 amplitude is not linear but, in fact, saturates at supra-maximal stimulation levels. Accordingly, and contrary to what has been published previously, achieving maximum muscle activation may produce a paradoxically inferior signal-to-noise ratio and in some cases result in an artificially small (or undetectable) corrected cVEMP amplitude. cVEMP amplitude either asymptotes (if maximum EMG amplitude saturation occurs at the same stimulus intensity as yields the maximum cVEMP amplitude), or the cVEMP can become smaller if EMG amplitude can increase further beyond the stimulus intensity that yields that largest P1-N1 amplitude. In the latter case the noise increases further to reach maximum and creates a disadvantageous signal (cVEMP) to noise (tonic EMG) ratio.

Significant Vestibular System Impairment Is Common in a Cohort of Elderly Patients Referred for Assessment of Falls Risk

Background: Falls in elderly patients are associated with morbidity, mortality, and cost to the health-care system. The development of falls risk assessment programs have represented a method of responding to what is known about injurious falls. The multidimensional assessments involve the comparison against normative data of a patient's performance on metrics known to influence the likelihood of future falls. The factors assessed usually include falls and medication history, measures of mentation, depression, orthostatic hypotension, simple or choice reaction time, gait stability, postural stability, and the integrity of the patient's vision, somesthetic, and vestibular senses.

Purpose: This investigation was conducted to measure the proportion of patients referred for falls risk assessment who have evidence of vestibular system impairment.

Research Design: Qualitative, retrospective review of data collected from 2003 to 2007.

Study Sample: The cohort was 185 consecutive patients referred for multidimensional assessments of falls risk.

Data Collection and Analysis: Patients underwent quantitative assessments of peripheral and central vestibular system function consisting of electro- or videonystagmography (i.e., ENG/VNG), and sinusoidal harmonic acceleration testing. Results of these tests were compared to normative data.

Results: We found that 73% of the sample who underwent vestibular system assessment had quantitative evidence of either peripheral or central vestibular system impairment.

Conclusions: Our results suggest that quantitative assessments of the vestibulo-ocular reflex should be conducted on patients who are evaluated for falls risk. These examinations should include at least caloric testing and, where available, rotational testing.

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.

The Effect of Recording Montage and Tone Burst Duration on Cervical and Ocular Vestibular Evoked Myogenic Potential Latency and Amplitude

Objectives The objectives of this study were (a) to investigate the optimal tone burst duration when recording the cervical vestibular evoked myogenic potential (cVEMP) and the ocular vestibular evoked myogenic potential (oVEMP) and (b) to determine whether monopolar recording influences the latency or amplitude of the cVEMP or the oVEMP. Method Fifteen subjects ( M = 27.7 years, SD = 6.73 years) participated in this study. The participants had no prior history of otological or neurological disease. Both oVEMPs and cVEMPs were recorded at a fixed stimulus level for stimulus durations of 2, 5, 10, and 25 ms. For both cVEMP and oVEMP, responses were obtained using a traditional differential recording montage and a monopolar recording montage. Results The cVEMP and the oVEMP had the greatest amplitude in the 2-ms stimulus condition. There was a statistically significant decrease in amplitude for durations greater than 2 ms. Monopolar and bipolar cVEMP and oVEMP latencies and amplitudes were not significantly different. Conclusion As stimulus duration increased beyond 2 ms, the amplitude of the response decreased for both the cVEMP and the oVEMP. There was no significant change in latency with increasing stimulus duration for either response. These results suggested the optimal stimulus duration for both the oVEMP and cVEMP is 2 ms, and there is no apparent advantage of using a bipolar recording technique.

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.

Assessment of Subjective Visual Vertical (SVV) Using the "Bucket Test" and the Virtual SVV System

OBJECTIVE

The purpose of this study was to describe the variability and test-retest reliability of a commercially available subjective visual vertical (SVV) system known as Virtual SVV (Interacoustics). In addition, the study aimed to compare the reliability of the Virtual system with a previously established bucket test of SVV.

STUDY DESIGN

Fifteen participants with normal hearing, normal middle ear function, and normal utricular function were included in the study. Each participant underwent static SVV testing using both the Virtual system and the bucket test. Subjects completed 2 testing sessions to determine test-retest reliability. For each test, data were collected with the head at 0°, tilted 45° to the right, and tilted 45° to the left.

SETTING

This study was conducted in a balance function laboratory embedded in a large, tertiary care otology clinic.

RESULTS

The mean SVV values obtained with the Virtual system were within 1°-2° from 0 with the head positioned at 0°, which is in agreement with many other studies of SVV with the head at 0° (Akin & Murnane, 2009; Halmagyi & Curthoys, 1999; Zwergal, Rettinger, Frenzel, Dieterich, & Strupp, 2009). Using the intraclass correlation coefficient, test-retest reliability of the Virtual system was excellent in the 45° left position and fair to good in the 45° right and 0° position. Test-retest reliability of the bucket test was poor in all head positions.

CONCLUSIONS

The Virtual system is a more reliable measure of static SVV than the bucket test. Therefore, the Virtual system could be utilized as a screening device for utricular dysfunction in busy clinical settings.

Oculomotor Assessment in Children

Oculomotor evaluation as part of videonystagmography is an integral tool in the assessment of vestibular function providing a global assessment of the neurological pathways associated with oculomotor function. The value of an oculomotor evaluation for pediatric evaluation is well established; however, many questions can also arise with the application to the pediatric population. Oculomotor function is age dependent which can have a significant effect on the test results obtain in children. The underlying neural substrates and age effects are discussed across the literature with specific results from recent research using clinical oculomotor equipment and protocols. The evidence suggests there are several key differences in the pediatric population compared with adults. These include longer saccade latencies, reduced smooth pursuit gain, increased optokinetic asymmetry, increased variability in all responses, and increased artifact in saccade and smooth pursuit testing.

Effect of Electrode Montage and Head Position on Air-Conducted Ocular Vestibular Evoked Myogenic Potential

PURPOSE

The purpose of this investigation was to identify the optimal recording parameters for evoking the ocular vestibular evoked myogenic potential (oVEMP) using air-conduction stimuli.

METHOD

Subjects were 17 otologically and neurologically intact adults (age: M = 24.18 years, SD = 1.91 years). The oVEMP responses were elicited using a 500-Hz tone burst air-conduction stimulus presented at an intensity of 95 dB nHL. The setting was a balance function laboratory that was part of a large tertiary care otology clinic.

RESULTS

The oVEMP electrode montage and body position that yielded the largest oVEMP amplitude was the belly-tendon montage (Sandhu, George, & Rea, 2013), recorded with the subject in the sitting position. The N1 latency recorded with the belly-tendon montage was significantly shorter than that recorded for the infraorbital montage in both the sitting and supine positions.

CONCLUSION

The belly-tendon recording montage with the subject sitting yields significantly larger oVEMP amplitudes and shorter N1 latencies than do traditional bipolar infraorbital recordings.

Artifact in Pediatric Oculomotor Findings during Videonystagmography: A Retrospective Analysis

BACKGROUND

Accurate measurement of oculomotor function using videonystagmography (VNG) is imperative for diagnosis and management of patients with reported dizziness. The oculomotor evaluation during VNG utilizes video-oculography providing valuable information regarding the central structures and pathways that control eye movements. Artifact may have an effect on the overall validity and reliability of VNG oculomotor tracings and can result from patient and/or recording errors. It is postulated that artifact could occur more frequently in the pediatric population due to both patient and equipment factors.

PURPOSE

The purpose of this study was to systematically evaluate the occurrence and impact of artifact on saccades, smooth pursuit, and optokinetic (OPK) testing in normal pediatric and adult subjects using commercially available clinical VNG equipment and standard clinical protocols for oculomotor testing.

RESEARCH DESIGN

The present study utilized a retrospective analysis of a repeated measures design.

STUDY SAMPLE

Oculomotor results from a total of 62 participants were analyzed. Portions of these data have been presented in a previous research study. Group 1 consisted of twenty-nine 4- to 6-yr-olds with an average age of 4.86 (SD = 0.88) yr. Group 2 consisted of thirty-three 22- to 44-yr-olds with an average age of 25.2 (SD = 5.34) yr.

DATA COLLECTION AND ANALYSIS

Raw oculomotor recordings were analyzed "offline" by a single masked, trained investigator. Each tracing was evaluated for instances of artifact including eye blinks, eye closure, eyes moving in opposite direction of the target, eye tracking software problems, and overall poor morphology. The number of instances of artifact were noted and recorded for each participant in both groups. Individual eye movements not affected by artifact were included for final analysis. Artifact rejection techniques were also compared.

RESULTS

The results indicated increased artifact for the pediatric group for saccade and smooth pursuit testing. Additionally, a significant decrease in instances of artifact was noted with an increase in age in months for both saccade and smooth pursuit findings. OPK results did not indicate any significant difference in instances of artifact between the pediatric and adult groups or any decrease in instances of artifact with increasing age in the pediatric group. Artifact rejection technique did not have a significant effect on oculomotor measures for either age group.

CONCLUSIONS

Pediatric patients exhibit increased instances of artifact during VNG oculomotor testing, specifically during saccade and smooth pursuit testing, at least for the 4- to 6-yr-old population. A general age effect was also noted in this age group, with decreased artifact noted with increasing age. Artifact rejection technique was not a significant factor suggesting standard compared based strategies may be sufficient for use in the pediatric population. Additional study into the effect of artifact on oculomotor results for infants to age 3 yr and ages 7- to 18-yr-old, in the disordered population, and with additional equipment manufacturers is needed to confirm these results and further describe the impact of artifact on oculomotor findings in the pediatric population.

Cervical and Ocular VEMP Testing in Diagnosing Superior Semicircular Canal Dehiscence

Objective To determine the sensitivity and specificity of ocular and cervical vestibular evoked myogenic potentials (VEMPs) in the diagnosis of superior semicircular canal dehiscence (SCD) and to describe the VEMP response characteristics that are most sensitive to SCD and compare the findings to previous reports. Study Design Case series with chart review. Setting Two tertiary neurotologic referral centers. Subjects and Methods Cervical and ocular VEMP peak-to-peak amplitudes and thresholds from 39 adult patients older than 18 years with surgically confirmed SCD were compared with 84 age-matched controls. Results Using receiver operating characteristic (ROC) curves, cervical VEMP (cVEMP) amplitudes, cVEMP thresholds, and ocular VEMP (oVEMP) amplitudes had areas under the curve of 0.731, 0.912, and 0.856, respectively, all of which were statistically significant ( P < .0001). For cVEMP thresholds, at the clinical equivalent ≤85-dB normalized hearing level (nHL) threshold, the sensitivity and specificity were 97.3% and 31.3%, respectively. At the ≤70-dB nHL threshold, the sensitivity and specificity were 73.0% and 94.0%, respectively. For oVEMP amplitudes >12.0 µV, the sensitivity and specificity were 78.6% and 81.7%, respectively. Conclusion Data from this multicenter study suggest that both cVEMP thresholds and oVEMP amplitudes remain good diagnostic tests for identifying SCD, with each test dependent on a number of factors. The sensitivity and specificity of these individual tests may vary slightly between centers depending on testing parameters used.