The diagnostic value of vestibular-evoked myogenic potential in patients with vestibular schwannoma

Vestibular Tests Related to Tumor Volume in 137 Patients With Small to Medium-Sized Vestibular Schwannoma

OBJECTIVE

The video head impulse test (vHIT) and cervical and ocular vestibular evoked myogenic potentials (cVEMP and oVEMP) are new methods for measuring peripheral vestibular function. The objectives of this study were to compare these tests and the traditionally used caloric test in patients with small and medium-sized untreated vestibular schwannoma (VS) and to measure the correlation between the tests' results and tumor volume.

STUDY DESIGN

National cross-sectional study.

SETTING

Tertiary university clinic.

METHODS

Prevalence of abnormal cVEMP, oVEMP, caloric test, and 6-canal vHIT results on the tumor side and the nontumor side were compared and related to tumor volume with regression analyses in 137 consecutive VS patients assigned to a wait-and-scan protocol in the period 2017 to 2019.

RESULTS

The sensitivity of 6-canal vHIT, caloric test, cVEMP, and oVEMP to detect vestibulopathy in VS patients was 51%, 47%, 39%, and 25%, respectively. Normal tests were found in 21% of the patients. The results of vHIT and caloric test were related to tumor volume, but this was not found for cVEMP and oVEMP.

CONCLUSION

The caloric test and 6-canal vHIT showed the highest sensitivity in detecting vestibulopathy in untreated VS patients. vHIT, and particularly the posterior canal, was limited with a high prevalence of abnormal results on the nontumor side. A combination of cVEMP and caloric test was favorable in terms of a relatively high sensitivity and low prevalence of abnormal results on the nontumor side. Larger tumors had a higher rate of pathology on caloric testing and vHIT.

Video Head Impulse Test Results in Patients With a Vestibular Schwannoma-Sensitivity and Correlation With Other Vestibular System Function Tests, Hearing Acuity, and Tumor Size

OBJECTIVE

No previous studies have investigated a vestibular function test battery combining the Video Head Impulse Test (VHIT), the caloric test, and the cervical vestibular evoked myogenic potential (cVEMP) test. The objective was to investigate the sensitivity of the three vestibular tests to the presence of a vestibular schwannomas (VS), and possible correlations between test results, hearing acuity, and tumor size.

STUDY DESIGN

Retrospective cohort study.

SETTING

University hospital.

PATIENTS

Fifty-nine patients with a unilateral VS.

INTERVENTION

Audio-vestibular tests; the VHIT, cVEMP, caloric irrigation, pure-tone audiometry, and speech discrimination.

MAIN OUTCOME MEASURE

Findings, sensitivity, and correlations between VHIT saccades and gain; cVEMP potentials, unilateral caloric weakness; hearing acuity.

RESULTS

The sensitivity for VS was 80% for the VHIT, 93% for the caloric test, and 73% for the cVEMP test. VHIT gain and saccades were associated, and both had a positive correlation to caloric function. Medium-sized tumors demonstrated the highest gain asymmetry while larger tumors were associated with saccades. There was a weak correlation between vestibular findings and hearing acuity.

CONCLUSION

The VHIT is sensitive to the occurrence of a VS, but less so than the caloric test, and vestibular function deteriorates to some extent with increasing tumor size. VHIT outcomes are positively correlated to caloric function, but only vaguely to cVEMP and hearing acuity. The combined vestibular function test battery reached a sensitivity of 97% to the occurrence of a VS and could thus potentially substitute MRI for tumor screening upon the diagnosis of an asymmetrical hearing loss.

Vibration-induced nystagmus and head impulse test screening for vestibular schwannoma

LEVEL OF EVIDENCE

II-2.

BACKGROUND

Vestibular schwannomas are benign tumors of the eight cranial nerve that may cause asymmetric sensorineural hearing loss (ASHL) and vestibular dysfunction.

OBJECTIVE

The aim of this study was to assess the role of the video head impulse test (vHIT) and vibration-induced nystagmus (VIN) test in diagnosing vestibular schwannoma in a population of patients with Asymmetric sensorineural hearing loss.

MATERIAL AND METHODS

For this prospective case-control study, 23 consecutive patients with ASHL and normal magnetic resonance were enrolled in the control group, and 33 consecutive patients with ASHL and vestibular schwannoma were enrolled in the case group. Gold standard was magnetic resonance imaging. Audiometry, vHIT, and VIN tests were performed for each patient. Significance of VIN and vHIT testing was determined by evaluation of their sensitivity, specificity, and correlation with vestibular function tests.

RESULTS

Regarding the vHIT, sensitivity and specificity were 45.5% and 82.6%, respectively, for horizontal canal gain, 60.6% and 87.6%, respectively, for posterior canal gain, and 45.5% and 78.3%, respectively, when analyzing superior canal gains. Regarding the VIN test, the sensitivity and specificity were 81.8% and 73.9%, respectively, when based on the presence of a VIN with any mastoid stimulation.

CONCLUSIONS

Our results suggest that using the VIN test may be an efficient approach to screen for vestibular schwannoma in patients with asymmetric sensorineural hearing loss.

SIGNIFICANCE

Our results suggest that using the VIN test may be an efficient approach to screen for vestibular schwannoma in patients with ASHL.

Audiovestibular Loss of Function Correlates in Vestibular Schwannomas

OBJECTIVES

The aim of the present study was to investigate the relationships between tumor size, hearing, and vestibular outcomes in patients with vestibular schwannomas (VSs).

MATERIALS AND METHODS

Adult patients (n=124) with unilateral extrameatal VS prior to surgery were included in the study. This was a retrospective cohort study of preoperative audiovestibular investigations including audiometry, discrimination test, caloric test, cervical vestibular evoked myogenic potential (c-VEMP), and ocular vestibular evoked myogenic potential (o-VEMP).

RESULTS

The difference between lesioned and non-lesioned ear was significant for all audiovestibular outcomes. The mean caloric deficit was 74%. No tumor sided o-VEMPs were elicited. Caloric deficit correlated with hearing loss measured with pure tone average and discrimination score. c-VEMP deficit was significantly associated with severe hearing loss and larger tumors.

CONCLUSION

The presence of VS leads to a significant deterioration of audiovestibular function in all objective measures. Caloric test and o-VEMPS are sensitive though unspecific measures of VSs. Increasing tumor size is not directly associated with hearing loss and only somewhat to vestibular deficit. However, audiovestibular findings are correlated.

Prevalence of vestibular dysfunction in patients with vestibular schwannoma using video head-impulses and vestibular-evoked potentials

We sought to investigate the utility of new non-invasive tests of semicircular-canal and otolith function that are usable in the neuro-otology office practice in patients with vestibular schwannoma. Fifty patients with vestibular schwannoma were assessed using a 5-item battery consisting of air-conducted cervical- and bone conducted ocular-vestibular-evoked myogenic potentials (AC cVEMPs and BC oVEMPs) and video head impulse testing (vHIT) in all three canal planes. VEMP asymmetry ratios, latencies, and vHIT gains were used to determine the test sensitivity, relationship with tumour size and the pattern of vestibular nerve involvement. The percentage of abnormalities for each of the five tests for the entire sample ranged between 36.2-61.7%. In 58.3 % of patients, test abnormalities were referable to both superior and inferior vestibular nerve divisions. Selective inferior nerve dysfunction was identified in 10.4% and superior nerve dysfunction in 12.5%. The remaining 18.8% of patients demonstrated a normal test profile. The sensitivity of the 5-item battery increased with tumour size and all patients with medium to large (>14 mm) schwannoma had at least two abnormal vestibular test result. Our results indicate that dysfunction of the superior and inferior vestibular nerve evolves in parallel for most patients with schwannoma. Unexplained vHIT and VEMP asymmetry should alert otologists and neurologists to undertake imaging in patients presenting with non-specific disequilibrium or vertigo.

Cervical vestibular-evoked myogenic potential in vestibular schwannoma after gamma-knife surgery

OBJECTIVE

Gamma-knife radiosurgery (GKS) for vestibular schwannomas (VSs) has become popular during the last two decades, and a promising tumor control rate has been reported. Therefore, the evaluation and preservation of auditory-vestibular nerve function after GKS have become more and more important in these patients with long-term survival. We have traditionally used pure-tone audiometry (PTA) for evaluation of auditory nerve function, and the caloric test for superior vestibular nerve function. Vestibular-evoked myogenic potential (VEMP) has recently emerged from various neurophysiological examinations for assessment of the integrity of the inferior vestibular nerve function. This novel tool has been established to represent a sacculo-collic reflex. By using these three tools, the auditory-vestibular nerve function of VS patients can be evaluated and monitored before and after GKS.

METHODS

Fourteen patients with unilateral VS that underwent GKS were prospectively recruited. All of them received a battery of auditory-vestibular function tests including PTA, caloric, and cVEMP tests before and after GKS at each time point (1, 6, and 12 months). Our data also included the tumor volumes and their relationship with the PTA, caloric, and cVEMP test results.

RESULTS

The PTA, caloric, and cVEMP tests showed abnormal results before GKS in 85.7%, 78.6% and 78.6% of our VS patients, respectively. The PTA, caloric, and cVEMP results did not show strong correlations between each other. However, there was a tendency that when the tumor grew larger, the auditory-vestibular function deficits became more severe. The PTA and cVEMP test results remained stable during the 1-year follow-up after GKS. However, the caloric test showed transient deterioration at the 6th month follow-up, which then recovered by the 1-year follow-up.

CONCLUSION

The combination of these three tests can help us diagnose VS and assess the change in auditory-vestibular nerve function during the post-GKS follow-up period. The results of these three tests were independent for smaller tumors, but all tests may show abnormal findings with larger tumors. Although the study is still ongoing, the preliminary data showed that GKS treatment would not affect the auditory-vestibular nerve function within a 1-year follow-up period.

Vestibular evoked myogenic potentials (VEMPs) in central neurological disorders

Several types of acoustic stimulation (i.e. tone bursts or clicks), bone-conducted vibration, forehead taps, and galvanic stimulation elicit myogenic potentials. These can be recorded in cervical and ocular muscles, the so called vestibular evoked myogenic potentials (VEMPs). The cervical VEMP (cVEMP) resembles the vestibulo-collic reflex and the responses can be recorded from the ipsilateral sternocleidomastoid muscle. The ocular VEMP resembles the vestibulo-ocular reflex and can be recorded from extra-ocular muscles by a surface electrode beneath the contralateral infraorbital margin. Initially, the literature concerning VEMPs was limited to peripheral vestibular disorders, however, the field of VEMP testing is rapidly expanding, with an increasing focus on central neurological disorders. The current literature concerning VEMP abnormalities in central neurological disorders is critically reviewed, especially regarding the methodological aspects in relation to quality as well as the clinical interpretation of the VEMP results. Suggestions for further research are proposed as well as some clinically useful indications.

The role of cervical and ocular vestibular evoked myogenic potentials in the assessment of patients with vestibular schwannomas

OBJECTIVES

To investigate the clinical utility of VEMPs in patients suffering from unilateral vestibular schwannoma (VS) and to determine the optimal stimulation parameter (air conducted sound, bone conducted vibration) for evaluating the function of the vestibular nerve.

METHODS

Data were obtained in 63 patients with non-operated VS, and 20 patients operated on VS. Vestibular function was assessed by caloric, cervical and ocular VEMP testing. 37/63 patients with conclusive ACS ocular VEMPs responses were studied separately.

RESULTS

In the 63 non-operated VS patients, cVEMPs were abnormal in 65.1% of patients in response to AC STB and in 49.2% of patients to AC clicks. In the 37/63 patients with positive responses from the unaffected side, oVEMPs were abnormal in 75.7% of patients with ACS, in 67.6% with AFz and in 56.8% with mastoid BCV stimulation. In 16% of the patients, VEMPs were the only abnormal test (normal caloric and normal hearing). Among the 26 patients who did not show oVEMP responses on either side with ACS, oVEMPs responses could be obtained with AFz (50%) and with mastoid stimulation (89%).

CONCLUSIONS

The VEMP test demonstrated significant clinical value as it yielded the only abnormal test results in some patients suffering from a unilateral vestibular schwannoma. For oVEMPs, we suggest that ACS stimulation should be the initial test. In patients who responded to ACS and who had normal responses, BCV was not required. In patients with abnormal responses on the affected side using ACS, BCV at AFz should be used to confirm abnormal function of the superior vestibular nerve. In patients who exhibited no responses on either side to ACS, BCV was the only approach allowing assessment of the function of the superior vestibular nerve. We favor using AFz stimulation first because it is easier to perform in clinical practice than mastoid stimulation.

Clinical uses of cervical vestibular-evoked myogenic potential testing in pediatric patients

To demonstrate the feasibility and clinical significance of cervical vestibular-evoked myogenic potential (cVEMP) test in pediatric patients.Retrospective review study was conducted in a pediatric tertiary care facility. A total of 278 patients were identified with adequate data, including medical notes, results of cVEMP, and imaging studies.Among the total of 278 pediatric patients, only 3 children were not able to finish the cVEMP test successfully. In about 90% of the cases, the cVEMP test was requested to investigate a patient's hearing loss and/or vestibular complaints. Over 90% of the cVEMP tests were ordered by specialists such as pediatric otolaryngologists or otologists. Obtained cVEMP results provided useful information in clinical diagnosis and management in all cases.It is feasible to conduct cVEMP testing in children, including infants, and cVEMP testing can provide valuable information in the diagnosis and management of hearing loss and vestibular impairment. This simple and noninvasive test should be embraced by pediatric professionals.

Vestibular evoked myogenic potential

Vestibular evoked myogenic potential (VEMP), is an electromyographic response of vestibular origin evoked by sound, vibration or electrical stimulation. VEMP is widely used as a clinical test of the otolith organs. Nowadays, two kinds of VEMP, cervical VEMP (cVEMP) and ocular VEMP (oVEMP) are clinically used. cVEMP is a test of sacculo-collic reflex while oVEMP is a test of utriculo-ocular reflex. Absence of responses, large interaural asymmetry of amplitudes, prolonged peak latencies, and abnormal thresholds of responses are regarded as abnormal responses. Clinical application to various diseases of the vestibular system was performed. Using VEMP, a new type of vestibular neuritis, inferior vestibular neuritis was established. A prominent feature of VEMP in Meniere’s disease is a shift of a preferred frequency in cVEMP. The whole aspects of VEMP findings in patients with benign paroxysmal positional vertigo are not clarified yet. Sensitivity of cVEMP to vestibular schwannoma was 80.0%, while specificity was 52.7%. Concerning diagnosis of superior canal dehiscence syndrome (SCDS), oVEMP to air-conducted sound is the most helpful. Augmentation of oVEMP responses is a prominent feature in SCDS. I also presented “idiopathic otolithic vertigo”, which I proposed as a new clinical entity based on VEMP findings. Some patients complained of lateral tilting sensation in the roll plane, or tilting or translational sensation in the pitch plane without rotatory vertigo. Majority of patients with these symptoms had absent or decreased responses of oVEMP and/or cVEMP. I proposed that these patients could be diagnosed as having “idiopathic otolithic vertigo”.

International guidelines for the clinical application of cervical vestibular evoked myogenic potentials: an expert consensus report

BACKGROUND

Cervical vestibular evoked myogenic potentials (cVEMPs) are electromyogram responses evoked by high-level acoustic stimuli recorded from the tonically contracting sternocleidomastoid (SCM) muscle, and have been accepted as a measure of saccular and inferior vestibular nerve function. As more laboratories are publishing cVEMP data, there is a wider range of recording methods and interpretation, which may be confusing and limit comparisons across laboratories.

OBJECTIVE

To recommend minimum requirements and guidelines for the recording and interpretation of cVEMPs in the clinic and for diagnostic purposes.

MATERIAL AND METHODS

We have avoided proposing a single methodology, as clinical use of cVEMPs is evolving and questions still exist about its underlying physiology and its measurement. The development of guidelines by a panel of international experts may provide direction for accurate recording and interpretation.

RESULTS

cVEMPs can be evoked using air-conducted (AC) sound or bone conducted (BC) vibration. The technical demands of galvanic stimulation have limited its application. For AC stimulation, the most effective frequencies are between 400 and 800 Hz below safe peak intensity levels (e.g. 140 dB peak SPL). The highpass filter should be between 5 and 30 Hz, the lowpass filter between 1000 and 3000 Hz, and the amplifier gain between 2500 and 5000. The number of sweeps averaged should be between 100 and 250 per run. Raw amplitude correction by the level of background SCM activity narrows the range of normal values. There are few publications in children with consistent results.

CONCLUSION

The present recommendations outline basic terminology and standard methods. Because research is ongoing, new methodologies may be included in future guidelines.

Role of cervical vestibular evoked myogenic potential response in identifying vestibular dysfunction

Objectives:

To analyse cervical vestibular evoked myogenic potential response parameters in normal volunteers and vertiginous patients.

Subjects and methods:

A prospective study of 50 normal subjects and 50 patients with vertigo was conducted at Chiang Mai University Hospital, Thailand. Cervical vestibular evoked myogenic potential responses were measured using air-conducted, 500-Hz, tone-burst stimuli with subjects in a sitting position with their head turned toward the contralateral shoulder.

Results:

The mean ± standard deviation age and male:female ratio in the normal (44.0 ± 9.3 years; 12:38) and vertigo groups (44.7 ± 9.8 years; 17:33) were not significantly different. The prevalence of absent responses in the normal (14 per cent) and vertigo ears (46 per cent) differed significantly (p < 0.0001). Other cervical vestibular evoked myogenic potential parameters (i.e. response threshold, P1 and N1 latency, P1–N1 interlatency and interamplitude, inter-ear difference in P1 threshold, and asymmetry ratio) showed no inter-group differences.

Conclusion:

The absence of a cervical vestibular evoked myogenic potential response is useful in the identification of vestibular dysfunction. However, patients should undergo a comprehensive battery of other vestibular tests to supplement their cervical vestibular evoked myogenic potential response findings.

Ocular vestibular evoked myogenic potentials in patients with acoustic neuroma

To assess the usefulness of vestibular testing in patients with acoustic neuroma, considering two main aspects: to compare diagnostic sensitivity of the current vestibular tests, especially considering ocular vestibular evoked myogenic potentials (OVEMPs) and to identify pre-operative localization of the tumor (inferior vestibular nerve vs. superior vestibular nerve) only with the help of vestibular electrophysiological data. Twenty-six patients with unilateral acoustic neuroma (mainly intracanalicular type) were studied with a full audio-vestibular test battery (pure tone and speech audiometry, caloric bithermal test, vibration-induced nystagmus test (VIN), cervical and OVEMPs). 18 patients (69 %) showed abnormal caloric responses. 12 patients (46.2 %) showed a pattern of VIN test suggestive of vestibular asymmetry. 16 patients (61.5 %) showed abnormal OVEMPs (12 only to AC, 4 both to AC and BC). 10 patients (38.5 %) showed abnormal cervical vestibular evoked myogenic potentials (5 both to AC and BC, 5 only to AC). In one case, results of vestibular evoked potentials and caloric test were confirmed by intra-operative and post-operative findings. Results of electrophysiological tests in AN patients could be helpful for planning the proper surgical approach, considering that sensitivity of every exam is quite low in intracanalicular lesion; clinical data allow a better interpretation of vestibular evoked myogenic potentials.

Correlation between caloric and ocular vestibular evoked myogenic potential test results

CONCLUSION

The ocular vestibular evoked myogenic potential (o-VEMP) test results correlate significantly with caloric test results for patients with acoustic neuroma (AN), but not for patients with Meniere's disease (MD), indicating that the o-VEMP test may replace the caloric test for evaluating the vestibular nerve from which the AN arises. Conversely, the caloric, o-VEMP, and cervical VEMP (c-VEMP) tests should be performed to map lesion sites in the vestibular labyrinth.

OBJECTIVE

This study performed caloric, o-VEMP, and c-VEMP tests on patients with central and peripheral vestibular disorders to investigate their relationships.

METHODS

In all, 66 patients comprising 16 with unilateral AN and 50 with unilateral definite MD were enrolled. All patients underwent caloric, o-VEMP, and c-VEMP tests.

RESULTS

In the AN group, the caloric test identified canal paresis and caloric areflexia in 10 ears, while the o-VEMP and c-VEMP tests identified abnormal (absent or delayed) responses in 12 and 11 ears, respectively. A significant correlation existed between caloric and o-VEMP test results, but not between caloric and c-VEMP test results, or between o-VEMP and c-VEMP test results. For the MD group, abnormal caloric, o-VEMP, and c-VEMP test results were obtained for 24%, 44%, and 38% of hydropic ears, respectively. No correlation existed between any two test results.

Comparison of Bone-Conducted Vibration for Eliciting Ocular Vestibular-Evoked Myogenic Potentials

Objective. This study compared bone-conducted vibration (BCV) stimuli at forehead (Fz) and mastoid sites for eliciting ocular vestibular-evoked myogenic potentials (oVEMPs).

Study Design. Prospective study.

Setting. University hospital.

Methods. Twenty healthy subjects underwent oVEMP testing via BCV stimuli at Fz and mastoid sites. Another 50 patients with unilateral Meniere’s disease also underwent oVEMP testing.

Results. All healthy subjects showed clear oVEMPs via BCV stimulation regardless of the tapping sites. The right oVEMPs stimulated by tapping at the right mastoid had earlier nI and pI latencies and a larger nI-pI amplitude compared with those stimulated by tapping at the Fz and left mastoid. Similar trends were also observed in left oVEMPs. However, the asymmetry ratio did not differ significantly between the ipsilateral mastoid and Fz sites. Clinically, tapping at the Fz revealed absent oVEMPs in 28% of Meniere’s ears, which decreased to 16% when tapping at the ipsilesional (hydropic) mastoid site, exhibiting a significant difference.

Conclusion. Tapping at the ipsilateral mastoid site elicits earlier oVEMP latencies and larger oVEMP amplitudes when compared with tapping at the Fz site. Thus, tapping at the Fz site is suggested to screen for the otolithic function, whereas tapping at the ipsilesional mastoid site is suitable for evaluating residual otolithic function.

Malignant paroxysmal positional vertigo

OBJECTIVE

An insidious percentage of paroxysmal positional vertigo appears to be intractable with canalith repositioning maneuver and also is not self-limiting. This type of positional vertigo is sustained by the action of intracranial tumors that mimics the clinical aspects of benign paroxysmal positional vertigo.Aim of this study is to clarify the features of these forms of positional vertigo, which we indicate as malignant paroxysmal positional vertigo.

METHODS

We retrospectively reviewed the clinical records of all the patients who presented with vertigo spells and were managed at our tertiary care referral centre over a three years period. Two hundred and eleven patients with diagnosis of positional paroxysmal vertigo were included in the final study.

RESULTS

Seven patients were affected by intracranial tumors causing a positional vertigo and were classified as malignant paroxysmal positional vertigo patients after radiological and histological diagnosis. These patients were affected by an internal auditory canal mass alone or with extension in the cerebello pontine angle that mimicked a benign positional vertigo.

CONCLUSION

We can conclude that the clinician should keep in mind the differentiation between benign positional vertigo and malignant positional vertigo. When the patients with positional vertigo presents a strange behaviour of symptoms, nystagmus or response to the canalith repositioning maneuver a radiological investigation must be undertaken in every doubtful case.

[Recording cervical and ocular vestibular evoked myogenic potentials. Part 2: influencing factors, evaluation of findings and clinical significance]

VEMP measurements are subject to various influencing factors: patient age, threshold, sound intensity and frequency. Using air (AC) and bone conduction (BC) the vestibular receptors and afferents of the otolith organs can be activated to varying degrees. Recordings of cervical (cVEMP) and ocular VEMP (oVEMP) are clinically possible. AC-cVEMP are primarily an indicator of the sacculocollic reflex pathway. Together with findings on the vestibuloocular reflex (VOR) and complimentary otolith tests, VEMP enable otolith function analysis of each side separately. In addition, the distinction between combined or isolated canal and otolith dysfunction in terms of subtyping and patterns of damage in mono- and bilateral disorders, such as vestibular neuritis or bilateral vestibulopathy, is possible. Moreover, VEMP is relevant in terms of prognostic and therapeutic considerations as well as expert assessments.

Vestibular-evoked myogenic potentials eliciting: an overview

Recently, the favoured approach for unilateral testing of saccular function is the recently developed method of vestibular-evoked myogenic potentials (VEMPs). VEMP testing is a reliable technique, since it selectively stimulates and investigates each lateral canal in isolation from the other, providing information for the assessment of otolith function and inferior vestibular nerve integrity. The aim of this study was to provide a current review of the different methods used to record VEMPs. We noticed discrepancies in relation to the ways used to record the VEMPs in relation to the following factors: types of stimuli used (clicks or tone bursts) and body muscles tested, patient position at the time of recording, response, type of phone used and way of stimulus presentation (mono or binaural, ipsi or contralateral) and others. As a conclusion, despite the numerous studies in the field, there is no consensus in the literature as to the best recording method for VEMPs. However, the new ocular VEMPs in response to bone conducted vibration seem to be of clinical importance for the evaluation of utricular function. Further research is needed to support its clinical usefulness.

Vestibular schwannoma with absent vestibular evoked myogenic potentials to clicks but normal ABR, caloric responses and vestibular evoked myogenic potentials to 500 Hz tone bursts

We report a case of vestibular schwannoma with absent vestibular evoked myogenic potentials (VEMPs) to clicks but normal auditory brainstem responses, caloric responses, and vestibular evoked myogenic potentials to 500 Hz tone bursts. This patient visited our clinic with complaint of sudden right hearing loss. This was the third episode of hearing loss in his right ear. Due to atypical medical history, he underwent further neuro-otological and neuroradiological examinations. Among the neurophysiological tests, only VEMPs to clicks showed abnormal findings (absent responses on the right). MRI revealed a small vestibular schwannoma in the right internal auditory meatus, which was considered to be of inferior vestibular nerve origin. This case suggested that VEMPs to clicks should still be included in the test batteries for the diagnosis of vestibular schwannoma.

Vestibular evoked myogenic potentials: past, present and future

Since the first description of sound-evoked short-latency myogenic reflexes recorded from neck muscles, vestibular evoked myogenic potentials (VEMPs) have become an important part of the neuro-otological test battery. VEMPs provide a means of assessing otolith function: stimulation of the vestibular system with air-conducted sound activates predominantly saccular afferents, while bone-conducted vibration activates a combination of saccular and utricular afferents. The conventional method for recording the VEMP involves measuring electromyographic (EMG) activity from surface electrodes placed over the tonically-activated sternocleidomastoid (SCM) muscles. The "cervical VEMP" (cVEMP) is thus a manifestation of the vestibulo-collic reflex. However, recent research has shown that VEMPs can also be recorded from the extraocular muscles using surface electrodes placed near the eyes. These "ocular VEMPs" (oVEMPs) are a manifestation of the vestibulo-ocular reflex. Here we describe the historical development and neurophysiological properties of the cVEMP and oVEMP and provide recommendations for recording both reflexes. While the cVEMP has documented diagnostic utility in many disorders affecting vestibular function, relatively little is known as yet about the clinical value of the oVEMP. We therefore outline the known cVEMP and oVEMP characteristics in common central and peripheral disorders encountered in neuro-otology clinics.