Elsevier

Clinical Neurophysiology

Volume 113, Issue 9, September 2002, Pages 1464-1469
Clinical Neurophysiology

Vestibular evoked myogenic potentials in multiple sclerosis patients

https://doi.org/10.1016/S1388-2457(02)00155-4Get rights and content

Abstract

Objectives: Vestibular evoked myogenic potentials (VEMPs) are saccular responses to loud acoustic stimuli and are recordable from the sterno-cleido-mastoid muscle ipsilaterally to the stimulated ear. This study aimed to investigate VEMPs in patients suffering from multiple sclerosis (MS), and to compare these findings with both clinical and instrumental data.

Methods: We recorded VEMPs from 70 MS patients, whose clinical data were retrospectively evaluated for the possible occurrence of: past and current (with respect to VEMP recording) brainstem and/or cerebellar symptoms; current brainstem and/or cerebellar signs. Sixty-five patients underwent brainstem auditory evoked potentials (BAEPs) recording; 63 of the same patients underwent saccadic eye movement recording and subjective visual vertical (SVV) evaluation.

Results: VEMPs were abnormal in 31%, BAEPs in 38% and SVV in 21% of the patients. Saccadic eye movements showed a possible brainstem dysfunction in 44.4% of the patients. There was no correlation between the occurrence of abnormalities and the technical means of detection. The same held true for correlations with clinical data, with the exception of the BAEPs; these proved to be more frequently abnormal in patients presenting at neurological examination with brainstem and/or cerebellar signs that were possibly related to the complaint of dizziness.

Conclusions: VEMPs should be considered a useful complementary neurophysiological tool for the evaluation of brainstem dysfunction.

Introduction

Vestibular evoked myogenic potentials (VEMPs) are obtained through the delivery of acoustic (or galvanic) stimuli that are able to trigger a vestibulo-spinal response (Bickford et al., 1964) by stimulating the saccular macula (Murofushi et al., 1995, Murofushi et al., 1996). The response may be recorded from surface electrodes placed over various neck or limb muscles. The first two peaks, labelled P13 and N23 on the basis of their polarity and their latency, depend on the integrity of vestibular afferents, and are almost invariably detectable (Colebatch et al., 1994).

VEMP recording is a simple, inexpensive and rapid method that is well tolerated by subjects, and easily implementable in a laboratory equipped for recording evoked potentials. Moreover, VEMP recording and subjective visual vertical (SVV) evaluation, the latter a measure of the ability to judge the orientation of the gravity vector without allocentric visual cues, provide reliable information about otolith function without very sophisticated equipment, such as that used to test the linear vestibulo-ocular reflex.

When recorded from the surface of the sterno-cleido-mastoid (SCM) muscles, VEMPs check the integrity of the saccular afferences to the brainstem vestibular nuclei, and then to SCM through the upper cervical segments and the accessory nerve.

To date the use of VEMPs in clinical settings has mainly involved patients suffering from vestibular end organ or vestibular nerve dysfunction, whereas there are only a few reports all very recent, concerning patients with brainstem lesions (Murofushi et al., 2001, Itoh et al., 2001, Shimizu et al., 2000).

This retrospective study aimed to evaluate the occurrence of abnormal VEMPs in a group of 70 MS patients, and to compare such occurrence with data both from other neurophysiological tests and from clinical history and examination.

Section snippets

Patients

Seventy unselected patients (mean age: 35.5 years; range 19–61 years) suffering from MS according to the diagnostic criteria recommended by the International Panel on the Diagnosis of MS (McDonald et al., 2001) underwent VEMP recording during hospitalization either for diagnostic purposes or for a relapse. At the time of VEMP recording the diagnosis of MS could be made in most of the patients on a clinical basis, and in those (6/70) in which this was not possible the diagnosis was confirmed by

Results

The past medical history of our patients suggested the occurrence of brainstem symptoms in 31.9% and of cerebellar symptoms in 14.5% of the patients. The current evaluation of the patients showed brainstem symptoms in 4.3% and signs in 23.2% of the patients, and cerebellar symptoms in 10.1% and signs in 27.5% of the patients. In particular, 14.5% of the patients complained of ‘dizziness’ as one (or the only) of their current symptoms.

VEMPs were detectable from both SCMs in 65 patients; in 3

Discussion

VEMPs are a muscular response obtained by galvanic or acoustic stimulation of the saccular macula. In cats both the sacculus and the utriculus show inhibitory connections to the ipsilateral SCM motoneurons (or to both ipsi- and contralateral motoneurons in the case of the utriculus) through the medial vestibular spinal tract (Kushiro et al., 1999). In humans also, the saccular connections are ipsilateral (Li et al., 1999) and inhibitory (Wu et al., 1999).

The abnormalities detected by the VEMPs

Acknowledgements

The authors would like to thank Mr Roberto Alloni, Mrs Maria Laura Delnevo and Miss Alessandra Spiritelli for their skilfull technical assistance.

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