Vestibular-evoked myogenic potentials eliciting: an overview

Positive and negative post stapedotomy effects on cervical VEMP recordings; a STROBE analysis

AIMS

The primary goal of the present study was to compare the pre- and post-stapedotomy elicitation and waveform characteristics of both air- and bone-conduction (AC-, BC-) cervical vestibular evoked myogenic potentials (cVEMPs) through an individualized approach. A possible association between audiological characteristics, such as AC- and BC- pure tone audiometry thresholds and air-bone gap and the production of cVEMPs before and after stapedotomy was also investigated.

MATERIAL AND METHODS

Twenty-five ears were subjected to full audiological evaluation as well as AC- and BC-cVEMPs pre- and post-stapedotomy. Four subgroups were studied; consistently present/absent, post-operatively disappeared and restored cVEMPs.

RESULTS

Post-stapedotomy changes in cVEMP elicitability did not reach significance for either AC-cVEMP (OR=5.41, 95% CI 0.88-33.36, P=0.06) or BC-cVEMP (OR=2.40, 95% CI 0.42-13.60, P=0.3). Normal or abnormal AC-cVEMPs were equally subject to post-operative changes (OR=1.95, 95% CI 0.32-12.01, P=0.5), as were BC-cVEMPs (OR=3.75, 95% CI 0.66-21.25, P=0.1). Neither the audiological characteristics nor the surgical outcome, in terms of ABG results, were relevant to the presence or absence of AC- and BC-cVEMPs before or after stapedotomy.

CONCLUSIONS

The presumed changes brought to the sacculus by stapedotomy are minor and beyond the diagnostic abilities of either AC-cVEMPs or BC-cVEMPs, both in terms of cVEMPs elicitability and waveform characteristics. In individual cases, however, which may deserve further investigation, cVEMPs may reappear or disappear after stapedotomy probably following minor changes toward a lower or higher vestibular system resistance for pressure and sound transmission.

Evaluation of the Vestibulocochlear System in Patients with Pseudoexfoliation Syndrome

Objectives

Patients with pseudoexfoliation syndrome (PES) can also have sensorineural hearing loss as well as balance problems. Our aim was to evaluate vestibulocochlear system involvement in PES patients.

Materials and Methods

The study included 16 subjects with PES (study group) with a mean age of 66.12±5.64 years and 17 healthy subjects (control group) with a mean age of 61.70±8.46 years. Both groups underwent ophthalmological, neuro-otological, audiological, and vestibular evaluation. Pure-tone audiometry and tympanometry were performed as audiological tests and bithermal caloric test and vestibular-evoked myogenic potential (VEMP) testing were used as vestibular tests. The Romberg, tandem Romberg, and Unterberger tests were also performed.

Results

In the PES group, bithermal caloric tests revealed right canal paresis in 6 patients, left canal paresis in 3 patients, and bilateral stimulation loss in 2 patients, despite no clinical evidence of balance loss. Paresis was not detected in any of the control subjects. Unilateral VEMP responses could not be obtained in 3 patients in the PES group. The ocular PES patients whose VEMP waves were obtained differed significantly from the control group (p<0.05). In office tests for vestibular evaluation, pathologic findings were found in 7 of 16 patients in the study group and only 4 subjects in the control group. Audiological evaluation with pure-tone thresholds revealed sensorineural decline at 4000 and 8000 Hertz in the PES patients. A statistically significant difference was found between the study group and the control group (p<0.05).

Conclusion

Patients with PES showed elevation in pure-tone thresholds and a decrease in superior and inferior vestibular nerve function, demonstrating that the vestibular system as well as the auditory system are affected in PES.

Vestibular cognition: State-of-the-art and future directions

Vestibular information has been traditionally considered as a specialized input for basic orienting behaviours, such as oculo-motor adjustments, postural control and gaze orientation. However, in the past two decades a widespread vestibular network in the human brain has been identified, that goes far beyond the low-level reflex circuits emphasized by earlier work. Because this vestibular cortical network is so widely distributed, it could, in principle, impact multiple neurocognitive functions in health and disease. This paper focuses on the relations between vestibular input, vestibular networks, and vestibular interventions by providing the authors' personal viewpoint on the state-of-the-art of vestibular cognitive neuropsychology, and its potential relevance for neurorehabilitation.

Children with posterior semicircular canal dehiscence: A case series

Posterior semicircular canal dehiscence is a rare condition and can cause a variety of symptoms. We report three cases of children between 5 and 12 years of age with a PSCD. They all presented with different complaints as follows: Tullio phenomenon in the first case, conductive hearing loss in the second and, conductive hearing loss and pulsatile tinnitus in the third. Imaging showed in all cases a PSCD on the right side, caused by a prominent jugular bulb (high riding bulb). We describe the clinical, audiometric and radiological findings, and discuss the management and therapy. A conservative "wait and see" approach is recommended, especially with children, because of the possible complications of surgery and the possibility that the symptoms will lessen with the skull base osseous maturation.

Bilateral Vestibulopathy in Superficial Siderosis

Background: Superficial siderosis (SS) is a rare condition in which hemosiderin, an iron storage complex, is deposited in neural tissues because of recurrent subarachnoid bleeding. Hemosiderin deposition in the vestibulocochlear nerve (CN VIII), brain, spinal cord and peripheral nerve can cause sensorineural hearing loss (SNHL) and postural imbalance, but much remains unknown about the vestibular manifestations of SS.

Objectives: To report the clinical course, cochleovestibular status, and patterns of vestibulopathy during follow-up of a relatively large case series, and to discuss the possible pathophysiological mechanism of vestibular deterioration.

Methods: Six patients diagnosed with SS by magnetic resonance imaging (MRI) were enrolled. Their medical records and radiological findings were retrospectively reviewed, particularly in terms of progression of the vestibulocochlear manifestations and the radiological characteristics.

Results: All six patients had SNHL. Five of them exhibited progressive hearing loss over years, which was asymmetric in four. On their most recent evaluations, patients showed cerebellar ataxia with combined central and peripheral vestibulopathy on both sides (n = 4), a bilateral peripheral vestibulopathy (n = 1) or isolated central vestibulopathy (n = 1). Notably, the former four patients showed an evolution of isolated central vestibulopathy into combined central and peripheral vestibulopathy. Hypo-intense lesions on T2 weighted MRIs were evident around the cerebellum in all patients, but such lesions were observed around the brainstem in five and the CN VIII in four. The cochlea-vestibular dysfunction generally progressed asymmetrically, but no left-right asymmetry was evident on MRI.

Conclusions: SS typically presents as bilaterally asymmetric, progressive cochleovestibular dysfunction with cerebellar ataxia. The pattern of vestibular dysfunction is usually combined central and peripheral vestibulopathy on both sides. Thus, precise identification of audiovestibular dysfunction and central signs is essential in SS, and patients with SS should undergo regular, comprehensive neurotological evaluation to optimize their treatments and prognosis.

Effects of acoustic stimulus duration on cervical vestibular evoked myogenic potentials: A neurophysiological and modeling study

OBJECTIVE

To analyze and model the effects of acoustic stimulus duration on cervical vestibular evoked myogenic potentials (cVEMPs).

DESIGN

Subjects with normal hearing and no vestibular or cervical disorders were tested using 1 kHz tone bursts (TBs) of different durations to evoke cVEMPs from the ipsilateral sternocleidomastoid muscle. VEMP modeling was performed in Labview.

RESULTS

The increase in TB duration initially resulted in a non-linear increase in cVEMP amplitude, followed by more complex cVEMP modifications that were mainly related to the appearance of a new wave (nX) that interfered with n23. With long TBs there were two distinct negative peaks with an identical threshold, suggesting a common vestibular nature. A two-level inhibition model qualitatively accounted for the two distinct negative peaks. However, good fitting of the cVEMP waveform required a multi-level model that included an excitatory phase after the inhibitory period.

CONCLUSIONS

The two negative components (n23 and nX) observed in cVEMPs elicited by long TBs may result from the involvement of two different pathways with different dynamics or a single pathway with quick adaptation in the activity along the vestibulo-collic arc. Excitatory activity following the period of inhibition may represent rebound activity at the motor unit level.

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.

On the impact of examiners on latencies and amplitudes in cervical and ocular vestibular-evoked myogenic potentials evaluated over a large sample (N = 1,038)

Vestibular-evoked myogenic potentials (VEMPs) are frequently used in the clinical diagnosis and research of vertigo syndromes. Altered latencies or amplitudes are typically interpreted as an indication of disturbance in the processing of vestibular stimuli along the otolithic pathways. Correct interpretation, however, can be difficult as VEMP amplitudes can vary greatly across subjects and across laboratories, likely because they are very sensitive to measurement conditions. Here, we attempted to quantify the impact of examiner differences on VEMP data. We collected data from 1,038 people using eight different experimental examiners, and investigated the effect of examiner on VEMP latencies and amplitudes. We found that the examiner collecting the data had a strong effect on outcome measures with significant differences (p < 0.001) in cVEMP and oVEMP latencies and in oVEMP amplitudes. No significant differences between examiners were found for the cVEMP amplitudes. When we compared the healthy and pathological sides of patients with a clinically diagnosed unilateral disease, no significant differences between sides were found. Given our results and the results reported in the literature, we conclude that the signal features of VEMPs are very sensitive to variables that may be influenced by the examiner. The field should therefore work on a better standard for VEMP recordings.

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.

cVEMPs: a systematic review and meta-analysis

OBJECTIVE

A systematic literature review and meta-analysis was performed to determine the effect of stimulus type, SCM muscle activation method, transducer type, and method to control SCM muscle EMG level on response parameter values for 0.1-ms click-evoked and 500-Hz tone burst cVEMPs. A description of normative response values was attempted.

DESIGN

An electronic systematic literature review was performed to obtain normative cVEMP response data. Subsequently a meta-analysis was conducted to determine significant effects on cVEMP response parameters and to obtain norms.

STUDY SAMPLE

Scopus was used to identify reports containing normative data. Reports were selected based on inclusion and exclusion criteria determined beforehand. Weighted means were calculated and compared to identify significant effects and normative data.

RESULTS

Sixty-six reports were included in the systematic review. Stimulus type, SCM muscle activation method, transducer type, and method to control SCM muscle EMG level had significant effects on all response parameters.

CONCLUSIONS

Optimal stimulus and recording parameters suggested by previous research are confirmed by the current systematic review and meta-analysis and are suggested for clinical use. Response parameter values are influenced by variations in stimulus and recording parameters and normative response values are suggested as guideline for cVEMP interpretation.

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.