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OtolaryngologyHead and Neck Surgery (2006) 135, 286-290

019doith a retrocochlerar lesion at an early stage and can be used inraoperative, neurophysiological monitoring.M rating: C-42006 American Academy of OtolaryngologyHead and Neckrgery Foundation. All rights reserved.

he vestibular-evoked myogenic potentials (VEMPs)have been described to be electromyographic (EMG)

ponses of the sternocleidomastoid muscle (SCM) uponh-level acoustic stimulation of the saccule. This so-

lled vestibulocollic reflex can be used in vestibular testing

MATERIALS AND METHODS

Patients and Study ProtocolIn a prospective study, 54 patients (26 women, 28 men; agerange 18-62 years, mean 43) were included from 2002 to2004. All patients gave their informed consent to participatein the study. The patients were diagnosed with (1) progres-sive hearing loss suitable for cochlear implantation (CIRIGINAL RESEARCH

he application of vestibuotentials in otoneurosurg

rne Ernst, MD, Ingo Todt, MD, Rainendreas Eisenschenk, MD, Alexanderietmar Basta, PhD, Berlin, Germany

JECTIVE: To evaluate the applicability of vestibular-evokedogenic potentials (VEMPs) in the diagnostics, intraoperative mon-ring, and postoperative follow-up of patients in otoneurosurgery.UDY DESIGN: A prospective study of patients who under-nt either cochlear implantation (CI, n 18) or were diagnosedth an acoustic neuroma (AN, n 9) or with neuro(micro)vas-ar compression of the VIIIth nerve (NVC, n 27) in the period02 to 2004. The follow-up was 1 year for all patients.TTING: A tertiary-referral unit.SULTS: VEMPs could be recorded in 64% of all patientsore CI and in 22% after surgery. The patients with AN had

rmal VEMPs in 22% of all cases when first diagnosed. NormalMPs were found in 37% of those patients with NVC. From theN patients who had to be operated, only 1 had intact VEMPs

er surgery. In contrast, after microvascular decompression allients (4) had normal VEMPs.NCLUSIONS: VEMPs are helpful in diagnosing patients

th vertigo to better identify saccular defects. They are highlysitive in the early diagnosis of retrocochlear lesions.From the Department Otolaryngology (Drs Ernst, Todt, Seidel, Bldow,Basta); and Microsurgery (Dr Eisenschenk); at UKB, Hospital of the

iversity of Berlin (Charit Medical School).Supported by a grant from the Sonnenfeld Foundation, Berlin, Germany.Presented at the Annual Meeting of the American Academy of Otolar-

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4-5998/$32.00 2006 American Academy of OtolaryngologyHead and Neck:10.1016/j.otohns.2006.03.006-evoked myogenicy

. Seidl, MD,dow, MD, and

otolith (saccular) function.1,2 It was shown that VEMPsn also be elicited in subjects with severe sensorineuralaring loss1 because they are not associated with the co-lear (hearing) function.3 VEMPs disappear after vestibu- deafferentation.1 The inferior vestibular nerve (IVN)rries the information from the saccule to the vestibularclei2 so that either a saccular loss or any interference with

IVN (eg, compression by a tumor, a contacting artery,d any other disease process of the cerebello-pontine anglePA]) should possibly impair the VEMP response. It wasrefore the aim of the present article to apply VEMPordings in different types of labyrinthine and retrochlear

thology. Moreover, the IVN was electrically stimulatedotoneurosurgery of the CPA to compare the findingsth those VEMPs elicited by acoustic stimulation. Weamined to what extent VEMPS contribute to audioves-ular diagnostics of neurotological patients and in in-operative monitoring during CPA surgery as suggested

4,5ologyHead and Neck Surgery, New York, NY, September 19-22,4.Reprint requests: Arne Ernst, Department of Otolaryngology at UKB,rener Str 7, D-12683 Berlin, Germany.E-mail address: ArneborgE@ukb.de.

Surgery Foundation. All rights reserved.

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287Ernst et al The application for VEMPs. . .up); (2) unilateral acoustic neuroma by MRI scanningthe first time, with symptoms of tinnitus and unsteadi-

ss, tumbling (AN group); or (3) neurovascular compres-n of the VIIIth nerve by magnetic resonance angiographythe brain (MRA) scanning with reports of attacks, typi-

lly of rotational vertigo (NVC group).6,7 The patientsre examined by an ENT specialist (including otoscopy)d underwent routine audiovestibular testing (Table 1)fore CT scanning (CI group), MRI scanning (AN group),MRA scanning (NVC group). All patients in the CI group 18) were implanted with Clarion 90k (Adv Bionics,lmar, CA).Four patients in the AN group (n 9) were put on aatch-and-wait list (MRI scanning each year, no surgicalervention unless their clinical symptoms deteriorated or

AN showed rapid growth toward the brainstem). Overperiod of the study, these tumors remained within the

ernal auditory canal (IAC). The tumors in the remainingatients of the AN group had an intra/extrameatal portion

d had to be resected because of their size and impinge-nt on the brainstem. They were operated on by using a

able 1udiovestibular test battery (in addition to VEMP

esting) applied in the AN group (IM, intrameatalcation of the AN watch-and-wait subgroup; IMEM, intra/extrameatal location of the AN surgery

ubgroup) and NVC group

Audiovestibular test

AN group (n 9) NVCgroup

(n 27)IM

(n 4)IM & EM(n 5)

ure-tone audiometry(mean hearingloss) 5 15 10

tapedial reflex testingNormal 1 1 9Lacking 3 4 18

EOAE recordingNormal 0 1 13Lacking 4 4 14BR recordingNormal 0 2 14Pathological 4 3 13

OR testingNormal 3 3 23Pathological 1 2 4

The mean hearing loss (in dB) is given as sum of hearingsses at 2, 3, 4 kHz divided by 3; the stapedial reflexes were

lacking when absent in more than half of all frequenciessted; transiently evoked otoacoustic emissions (TEOAE)ere lacking when absent in more than 3 frequencies; ABR

ecording was pathological when the interaural, interpeakifference of J5 exceeded 0.2 milliseconds; and VOR testingas pathological when cold-water irrigation showed a5% interaural difference.rosigmoid approach.res

seeTwenty-three of the patients in the NVC group (n 27)re given drug treatment (beta-blockers, carbamazepine,medical decompression) after confirmation of the di-

nosis by evidencing an anterior inferior cerebellar arteryICA) loop around the VIIIth cranial nerve by MRA. Fourtients failed to respond to drug therapy and thereforederwent microvascular decompression of the VIIIth nerveusing IVALON (M-Pact, Eudora, Kansas, USA).The study protocol was approved by our institutionaliew board. The patients gave their written, informed

nsent to participate in the study.

MP Testing and Data EvaluationMP testing for saccular function was performed as de-ibed earlier2 by bone-conducted acoustic stimuli. Inef, the stimuli (85-dB SPL, 0.1 millisecond, 520 clicks/cle) were delivered through a bone conductor, and thectromyogram of the SCM was recorded ipsilaterally (sur-e EMG electrodes were placed on the upper half of eachM and reference/ground electrodes at the upper sternum

d the central forehead). VEMP recordings were per-med during the patients first visit and 1 year after re-ssion (Fig 1).In those patients (n 9) who underwent surgery of theA for AN removal (n 5) or microvascular decompres-n (n 4), intraoperative VEMP recording was performed direct electrical stimulation of the exposed IVN (Fig 1).fore surgery, subdermal needle electrodes (Xomed Inc,shville, TN) were placed in the middle of the ipsi- andntralateral SCM (active) of each patient. The upper ster-m was used again (as described earlier) as a reference,d the ground electrode was attached at the forehead. Thectromyograms recorded measured from both musclesre amplified (sensitivity 500 V), filtered (bandpass 30-

ure 1 (A) Averaged (90x) EMG reponse of the ipsilateralrnocleidomastoid muscle on electrical stimulation of the inferiortibular nerve (threshold stimulus 0.4 mA). (B) Typical VEMP

ponse on acoustic stimulation by bone conduction. (For details,Materials and Methods and Results sections).

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288 OtolaryngologyHead and Neck Surgery, Vol 135, No 2, August 200600 Hz) (Madison, WI, USA), averaged (n up to 130),d stored (Viking IV; Nicolet). Only electrodes with anpedance of1.5 k were used for the recordings. Duringrgery, bipolar electric stimuli were applied to the IVN andperior part of the vestibular nerve by a concentric bipolarctrode (Xomed Inc, Nashville, TN). The current pulses,ich were generated by the Viking IV system, ranged inplitude from 0.4 to 1 mA, with a duration of 0.2 milli-ond and a frequency of 4.7 Hz.The follow-up period of the patients was 1 year. In the

and NVC groups, the audiovestibular and VEMP testults from the healthy, unaffected side of each patientre taken as individual controls. The VEMP results of thegroup were compared with age- and sex-related, healthy,

rmal-hearing controls. Statistical evaluation was per-med by a paired t test (P 0.01) (SPSS 10.0; SPSS Inc,icago, IL).

SULTSe CI Groupthe CI group (n 18), VEMP responses were absent in% of the patients before implantation. This increased to% after the operation (Table 2). Despite this significantrease of VEMP loss as a result of CI electrode insertion,caloric VOR responses were found to be normal in 82%

all patients (ie, compared with the nonoperated ear).The subjective complaints of the patients, which re-ined unchanged for at least 6 months postoperatively,re typically of slipping and tumbling sensations. A

stematic workup of these symptoms (eg, Dizziness Hand-p Inventors (DHI) was not undertaken.

e AN Group

able 2EMP test results in all patients (CI, AN, NVCroup) at the patients first visit and after 1 yearacoustically elicited VEMPs by bone-conductedound) and VEMPs by electrical stimulation of theN in operated patients (n 9) (5 AN, 4 NVC

atients)

VEMP test results(n 54)

CIgroup

(n 18)

ANgroup(n 9)

NVCgroup

(n 27)

irst visitVEMPs elicitable 12 2 17No VEMPs 6 7 10ne year follow-upVEMPs elicitable 4 3 21No VEMPs 14 16 6

For details, see Materials and Methods and Resultsections.e AN subgroup (n 4) with small intrameatal tumorsatch and wait) showed statistically significant changes ofmpared with their contralateral, nonaffected ears) in sta-dial reflex, Transitory Evoked Otoacoustic EmissionsEOAE), and Auditory Brainstem Response AudiometryBR) recordings (Table 1). VEMPs were absent in alltients. These test results had not changed after 1 yearable 2).Preoperative testing in the AN subgroup with intra/trameatal tumor extension (n 5), who subsequentlyderwent AN removal, yielded statistically significant, patho-ical test results in stapedial reflex and TEOAE recordings

able 1). V E M P s could not be evidenced in 3 patientsoperatively, but 1 patient showed normal VEMP record-s 1 year after surgery (Table 3 and Fig 1).

e NVC Groupe NVC group (n 27) showed statistically significant,thological results for stapedial reflex testing only (Table 1).MPs could not be elicited in 63% (Table 2). This ististically significantly different from the contralateral,naffected ears of this group. The 1-year follow-up showed

changes in VEMP testing in that subgroup of NVCtients who were treated by drug combinations (n 23)able 2). However, all patients who underwent microvascularcompression surgery (n 4) had normal VEMPs after 1ar (Table 3).

rect Electrical Stimulation of the IVNall patients (n 9), VEMPs could be elicited by intra-erative electrical stimulation of the IVN (Fig 1) even ifoperative acoustic stimulation failed to elicit a VEMPponse (n 6) (Table 2). The VEMP amplitudes wereearly related to stimulus intensity (Fig 1). The meanencies were 9.1 (2.2) milliseconds for P13 and 13.22.3) milliseconds for N23. The EMG responses to elec-

cal stimulation of the IVN were similar in amplitude butt in latency to those elicited by acoustic stimulation (Figsnd 2). No responses were observed in the contralateralM derivation. No EMG responses were found, neitherilaterally nor contralaterally, during electrical stimulationthe superior part of the vestibular nerve. In those cases inich the IVN was preserved during otoneurosurgery,MPs could be elicited by electrical stimulation through-

t the surgical procedure and subsequently during postop-tive testing with acoustic stimulation (Tables 2 and 3).

SCUSSION

e use of VEMP responses as a test of saccular functions become established over the last decade.1 Our resultsow that saccular defects and/or the compression of theN by acoustic neurinoma (which frequently originatesm this nerve [branch]) or an artery (eg, AICA) can induceoss of acoustically elicited VEMPs on the diseased side.

In 36% of the examined CI group, preoperative absenceVEMPs was observed. Some of these patients also suf-

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289Ernst et al The application for VEMPs. . .ed from connexion 26associated progressive, sensori-ural hearing loss. A cochleosaccular defect has alreadyen described by temporal bone histopathology.8 The post-erative VEMP loss in the majority of the implanted pa-nts is probably because of the surgical trauma after co-leostomy and electrode insertion. This finding couldplain why some of the (elderly) patients have a longstand-

history of unsteadiness and/or tumbling sensations,ich, despite having been reported in the literature,9,10 hast yet been adequately explained. One group suspected thevelopment of a delayed endolymphatic hydrops11 andinted out that the preoperative Vestibulo-Ocular ReflexOR) recordings have a limited relevance for predicting

occurrence of postoperative vertigo. Another group re-rted normal utricular function (the otolith organ consistssaccule and utricle) after cochlear implantation12 and

ncluded that the primary origin of postoperative vertigould be the preoperative meningitis that had destroyed theyrinths of both sides per se. However, these authors didt investigate saccular function. Loss of saccular functionpears difficult to rehabilitate, even after 1 year of train-.13 This could possibly explain the long-term vertiginous

mplaints of some implantees.11Acoustic neuromas frequently originate from the IVN

d have been reported to be accompanied by a preoperativeMP loss.5,14 Our small AN subgroup with purely in-

meatal tumors of the IAC still had normal hearing butnificantly changed VEMPs (4 pathological, 1 normal); indition, audiovestibular test results (stapedial reflex, TEOAEd ABR) proved pathological. In contrast, the subgroupth intra/extrameatal tumors had complete VEMP loss butrmal ABR recordings in 2 of the 5 cases. This finding ist in line with that of Tsutsumi et al,15 who reported a

able 3EMP test result comparison of operated/nonoperated pubgroup) and NVC (drug therapy and microvasculartimulation (preoperatively/postoperatively) on direct inf patients)

VEMP test resultsWatch

(n

coustically elicited VEMPsFirst visit (preoperative)

VEMPs elicitableNo VEMPs

One-year follow-up (postoperative)VEMPs elicitableNo VEMPs

lectrically elicited VEMPs (intraoperatively)VEMPs elicitableNo VEMPs

For details, see Materials and Methods and Results sections.se correlation of VEMP and ABR recordings in ANtients. However, the authors did not indicate the size and

wa

resation of the tumors under investigation. The postopera-e reappearance of VEMPs in 1 of our operated patients isicative of a surgically preserved IVN. Besides the benefit

the patient, this is of particular interest as an intraoperative,urophysiological monitoring method to guide the surgeon, definition of the plane of dissection within the VIIIth

rve), similar to the technique described for the facialrve.16

Neurovascular compression of the VIIIth nerve was con-med by MRA scanning.6 In brief, a definite contactingery (AICA) had to be identified, either at the root entryne of the brain stem or along the VIIIth nerve in the CPAalong (into) the nerve into the IAC.7 The most interestingding in this group was the lack of stapedial reflex re-onse in 66% of the patients and the absence of VEMPponses in 63%. Nerve compression (as in the subgroup oframeatal ANs above) seems to affect primarily theustico-facial fibres and the IVN,17 but the site of com-ssion depends on the localization of the neurovascular

ntact.7 The VEMPs of the patients operated on in thesent study (microvascular decompression) appeared to

ve recovered completely. Only the VEMP responses ofsubgroup of NVC patients with drug therapy (medical

compression) remained unchanged after 1 year.Intraoperatively, direct electrical stimulation of the IVNs performed successfully in all patients who were oper-d on (4 with AN resection and 5 with microvascularcompression). Interestingly, electrically evoked VEMPsuld be observed in those patients who did not showMP responses to acoustic stimulation before surgery.18ilar to a previous report,19 VEMP responses recovered

stoperatively in 1 AN patient.The electrical stimulus threshold for VEMP response

ts of the AN (watch-and-wait and resectionmpression, MVD subgroup) groups on acousticrative stimulation of the IVN (n number

N group NVC group

ait Resection(n 5)

Drug therapy(n 23)

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VESimpos aproximately 0.4 mA. The intraoperative VEMPponses correlated well in shape but not in latencies (for

P13 and N23) with the responses to acoustic stimulation.The electrical stimulation of the IVN resulted in signifi-cantly decreased latencies because of the direct suprathresh-old stimulation without the contributions of the vestibular-collic reflex arc (receptor excitation, synaptic transmission,and so on).

By using this approach, preservation of the IVN can bemonitored successfully in neuroma resection18 to preventunintended postoperative sequelae, such as unsteadiness,dizziness in the dark, and other symptoms of otolith disor-ders13 and to increase the surgeons and patients safety.Moreover, the cleavage plane and dissection strategy can beoptimized19 by this additional tool in intraoperative, neuro-physiological monitoring.16

This article is dedicated to Vittorio Colletti, MD (Verona,Italy), a brilliant surgeon and pioneer in intraoperative neurophys-iological monitoring.

REFERENCES

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5. Patko T, Vidal PP, Vibert N, et al. Vestibular evoked myogenicpotentials in patients suffering from an unilateral acoustic neuroma: astudy of 170 patients. Clin Neurophysiol 2003;114:134450.

6. Ryu H, Yamamoto S, Sugiyama K, et al. Neurovascular compressionsyndrome of the eighth cranial nerve: what are the most reliablediagnostic signs? Acta Neurochir (Wien) 1998;140:127986.

7. Ryu H, Yamamoto S, Sugiyama K, et al. Neurovascular compressionsyndrome of the eighth cranial nerve: can the site of compressionexplain the symptoms? Acta Neurochir (Wien) 1999;141:495501.

8. Tsuzuku T, Kaga K, Kanematsu S, et al. Temporal bone findings inkeratits, icthyosis and deafness syndrome. Ann Otol Rhinol Laryngol1992;101:4136.

9. Kubo T, Yamamoto K, Iwaki T, et al. Different forms of dizzinessoccurring after cochlear implantation. Eur Arch Otorhinolaryngol2001;258:912.

10. Steenerson RL, Cronin GW, Gary LB. Vertigo after cochlear implan-tations. Otol Neurotol 2001;22:8423.

11. Fina M, Skinner M, Goebel JA, et al. Vestibular dysfunction aftercochlear implantation. Otol Neurotol 2003;24:23442.

12. Vibert D, Hausler R, Kompris M, et al. Vestibular function in patientswith cochlear implantations. Acta Otolaryngol Suppl 2001;545:2934.

13. Ernst A, Basta D, Seidl RO, et al. Management of posttraumaticvertigo. Otolaryngol Head Neck Surg 2005;132:5548.

14. Murofushi T, Matsuzaki M, Mizuno M. Vestibular evoked myogenicpotentials in patients with acoustic neuromas. Arch Otolaryngol HeadNeck Surg 1998;124:50912.

15. Tsutsumi T, Komatsuzaki A, Noguchi Y, et al. Postoperative vestib-

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290 OtolaryngologyHead and Neck Surgery, Vol 135, No 2, August 2006Colebatch JG, Halmagyi GM. Vestibular evoked myogenic potentialsin human neck muscles before and after unilateral vestibular deaffer-entation. Neurology 1992;42:16356.Welgampola M, Rosengren SM, Halmagyi GM, et al. Vestibularactivation by bone conducted sound. J Neurol Neurosurg Psychiatry2003;74:7718.Cazals Y, Aran JM, Erre JP, et al. Neural responses to acousticstimulation after destruction of cochlear hair cells. Arch Otorhinolar-yngol 1979;224:6170.Magliulo G, Gagliardi M, Appiani GC, et al. Preservation of thesaccular nerve and of the vestibular evoked myogenic potential duringvestibular schwannoma surgery. Otol Neurotol 2003;24:30811.ular-evoked myogenic potentials in cases of verstibular schwannomas.Acta Otolaryngol 2001;121:4903.Lenarz T, Ernst A. Intraoperative facial nerve monitoring in the sur-gery of cerebello-pontine angle tumours: improved preservation ofnerve function. ORL J Otorhinolaryngol Relat Spec 1994;56:315.Moller AR. Vascular compression of cranial nerves: II: pathophysiol-ogy. Neurol Res 1999;21:43943.Tsutsumi T, Komatsuzaki A, Noguchi Y, et al. Prediction of the nervesof origin of vestibular schwannomas vestibular evoked myogenic po-tentials. Am J Otol 2000;21:7125.Chen CW, Young YH, Tseng HM. Preoperative versus postoperativerole of vestibular-evoked myogenic potentials in cerebellopontine an-gle tumor. Laryngoscope 2002;112:26771.

The application of vestibular-evoked myogenic potentials in otoneurosurgeryMATERIALS AND METHODSPatients and Study ProtocolVEMP Testing and Data Evaluation

RESULTSThe CI GroupThe AN GroupThe NVC GroupDirect Electrical Stimulation of the IVN

DISCUSSIONREFERENCES