Optimizing Stimulus Repetition Rate for Recording Ocular Vestibular Evoked Myogenic Potential Elicited by Air-Conduction Tone Bursts of 500 Hz

Simultaneous Multifrequency (SiMFy) Stimulus: A Novel and Reliable Stimulus for Frequency Tuning of Ocular Vestibular-Evoked Myogenic Potentials

BACKGROUND

Frequency tuning of ocular vestibular evoked myogenic potential (oVEMP) refers to the frequency of tone burst that produces the largest amplitude oVEMP. There is an ever-growing pool of published studies that found the frequency tuning of oVEMP distinctly different in Ménière's disease than the age-matched controls and benign paroxysmal positional vertigo. However, recording oVEMP in response to many frequencies makes an already lengthy vestibular test battery even more cumbersome and time-consuming.

PURPOSE

The aim of this study was to develop a novel time-saving stimulus that produces reliable results.

RESEARCH DESIGN

Prospective study.

STUDY SAMPLE

The study included 25 young, healthy adults.

DATA COLLECTION

The tone-bursts of 2000, 1500, 1000, 750, 500, and 250 Hz were generated and sequenced in this order to prepare a stimulus for simultaneous multifrequency (SiMFy) oVEMP. The response parameters of SiMFy and conventional oVEMP methods were compared.

RESULTS

No significant difference in peak-to-peak amplitude and frequency tuning existed between conventional and SiMFy oVEMP (p > 0.05). SiMFy had better test-retest reliability and was less time-consuming than the conventional oVEMP.

CONCLUSIONS

SiMFy is a time-saving and reliable stimulus for obtaining frequency tuning of oVEMP with no compromise on the outcomes. It can be immediately applied in most commercially available evoked potential systems with a facility for loading an external stimulus.

Simultaneous Multifrequency (SiMFy) Stimulus: A Novel and Reliable Stimulus for Frequency Tuning of Ocular Vestibular-Evoked Myogenic Potentials

Background Frequency tuning of ocular vestibular evoked myogenic potential (oVEMP) refers to the frequency of tone burst that produces the largest amplitude oVEMP. There is an ever-growing pool of published studies that found the frequency tuning of oVEMP distinctly different in Ménière's disease than the age-matched controls and benign paroxysmal positional vertigo. However, recording oVEMP in response to many frequencies makes an already lengthy vestibular test battery even more cumbersome and time-consuming.

Purpose The aim of this study was to develop a novel time-saving stimulus that produces reliable results.

Research Design Prospective study.

Study Sample The study included 25 young, healthy adults.

Data Collection The tone-bursts of 2000, 1500, 1000, 750, 500, and 250 Hz were generated and sequenced in this order to prepare a stimulus for simultaneous multifrequency (SiMFy) oVEMP. The response parameters of SiMFy and conventional oVEMP methods were compared.

Results No significant difference in peak-to-peak amplitude and frequency tuning existed between conventional and SiMFy oVEMP (p > 0.05). SiMFy had better test–retest reliability and was less time-consuming than the conventional oVEMP.

Conclusions SiMFy is a time-saving and reliable stimulus for obtaining frequency tuning of oVEMP with no compromise on the outcomes. It can be immediately applied in most commercially available evoked potential systems with a facility for loading an external stimulus.

Characterizing the impact of advancing age on 500 Hz tone-burst evoked ocular-vestibular evoked myogenic potentials

PURPOSE

Ageing is process that brings about steady decline in most of the systems, and vestibular system is no different. Although the effects of advancing age on the functioning of the semicircular canals and saccule has been well explored, its impact on the utricle remains the least studied component. While some researchers have investigated the effect of advancing age on the utricular functioning by virtue of studying ocular-vestibular evoked myogenic potentials (oVEMP), the use of smaller sample sizes would hamper the generalization of their results. Therefore, the present study aimed at investigating the effect of advancing age on oVEMP using a substantially larger sample size than the predecessors.

METHODS

A total of 480 individuals in the age range of 10-70 years were used as participants and were divided into six age groups, each one defined as a decade. Contralateral oVEMPs were elicited by 500-Hz tone-bursts and averaged over 200 sweeps to obtain the final waveform.

RESULTS

There was a significant decline in the response rates, prolongation of latencies and reduction of peak-to-peak amplitude of oVEMP with increasing age after 50 years (p < 0.05). However, there was no significant difference among the age groups until 50 years of age on any of these parameters (p > 0.05). Further, there was no significant change in inter-aural amplitude difference ratio with increasing age (p > 0.05).

CONCLUSION

The results of the study confirm significant impact of the ageing process on oVEMP after the age of 50 years and, therefore, age appropriate norms should be considered when using oVEMP for investigating utricular functioning in an individual, especially after the age of 50 years.

Elevated ocular VEMP responses in the absence of a superior semicircular canal dehiscence

BACKGROUND

Vestibular evoked myogenic potentials (VEMPs) have an accepted role in the diagnosis of the superior semicircular canal dehiscence (SSCD) syndrome. The current impression is that ocular VEMPs (oVEMPs) are more sensitive than cervical VEMPs (cVEMPs) for detecting a SSCD and that oVEMP testing in response to air conducted sound provides an excellent screening test without risk of radiation exposure from computerized tomography (CT).

AIMS/OBJECTIVES

To report on patients with elevated oVEMP amplitudes but without evidence for a SSCD on multiplanar CT imaging.

MATERIAL AND METHODS

Retrospective chart review of all patients referred for vestibular function testing to our department. Patients with oVEMP peak-to-peak amplitudes ≥17 μν without evidence for a SSCD on imaging were evaluated.

RESULTS

26 patients had oVEMP peak-to-peak amplitudes ≥17 μν with no evidence of a SSCD on imaging. The most common diagnosis was Meniere's disease in those identified.

CONCLUSION AND SIGNIFICANCE

oVEMPs can provide false positive results for diagnosis of a SSCD and an elevated oVEMP amplitude in itself is insufficient for diagnosis of a SSCD.

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.

A Novel Stimulation Paradigm for Obtaining Interfrequency Amplitude Ratio of Ocular Vestibular Evoked Myogenic Potentials

Purpose Interfrequency amplitude ratio (IFAR), the ratio of amplitude between ocular vestibular evoked myogenic potentials (oVEMPs) for tone bursts of 500 and 1000 Hz, aids in identification of Ménière's disease with high sensitivity and specificity. However, it requires recording of oVEMP for 2 frequencies, which doubles the time of recording. Use of simultaneous recording of responses for both frequencies could potentially bring down testing time. Simultaneous recording might be possible by modifying the oddball paradigm and using a ratio of 1:1 for the 2 frequencies. This might also reduce variation in oVEMP amplitude between frequencies due to changes in gaze angle between the recordings. However, it remains to be explored whether or not the use of modified oddball paradigm to record oVEMP (MoVEMP) will produce comparable responses to conventional sequential recording of oVEMP (CoVEMP) for obtaining IFAR. Hence, the study aimed to compare MoVEMP and CoVEMP on various measures of oVEMP. Method The study included 29 healthy adults in the age range of 18-30 years, 23 of which were used for validation and 6 for finding test-retest reliability. All participants underwent contralateral oVEMP recording using 500- and 1000-Hz tone bursts presented using MoVEMP and CoVEMP paradigms. Results Comparable outcomes on latencies, amplitude, and IFAR were obtained between CoVEMP and MoVEMP. Furthermore, MoVEMP took significantly lesser time per ear and also produced better test-retest reliability than CoVEMP. Conclusion MoVEMP is a quicker and more reliable clinical stimulation paradigm for obtaining IFAR than CoVEMP.