The effect of rise/fall time on vestibular-evoked myogenic potential triggered by short tone bursts

Vestibular-evoked myogenic potentials (VEMPs) are used more and more frequently as a clinical tool to test if the sacculocollic reflexes are intact in patients. They can be evoked by short tone bursts (STBs) as well as by clicks. Although most previous studies used traditional clicks to generate VEMP responses, our clinical experience showed that STBs were prone to evoke them more clearly, at least in some patients. Four kinds of STB stimulation patterns in a random order were used to test 22 ears using changing rise/fall times (0.3, 1, 3 and 10 ms). VEMP responses (p13/n23) triggered by these patterns were clearly observed in all 22 ears. When the rise/fall time was prolonged from 0.3 to 10 ms, the p13 latency was prolonged in parallel. There was a similar trend for the n23 latency, although a significant difference was not attained between 0.3 ms and 1 ms rise/fall times. Considering the p13 and n23 latencies for the 4 rise/fall times, the variances were smallest for the 1 ms stimulation, meaning that it caused the smallest interaural latency differences. The amplitude or relative amplitude in the individual ears tested was lowest for the 10 ms stimulation, being comparable among the other 3 rise/fall times. In conclusion, the 1 ms rise/fall time was a remarkable stimulation pattern because its VEMP responses were simultaneously more constant and conspicuous.

Diagnostic value of prolonged latencies in the vestibular evoked myogenic potential

BACKGROUND

As a parameter for the evaluation of the vestibular evoked myogenic potential (VEMP), amplitude has been used clinically. However, the significance of latency has not been considered.

OBJECTIVE

To clarify the diagnostic value of latencies of the VEMP.

DESIGN

We reviewed records of the VEMP of patients with various diseases and compared them with records of healthy volunteers.

SETTING

Data were collected from patients in an outpatient clinic of a tertiary care center and healthy volunteers.

SUBJECTS

Clinical records of 134 patients (61 men and 73 women, aged 20-75 years) were reviewed. Diagnoses were Meniere disease in 43 patients, acoustic neuroma in 62 patients, vestibular neuritis in 23 patients, and multiple sclerosis in 6 patients. Also, 18 healthy volunteers (13 men and 5 women, aged 25-38 years) were enrolled.

INTERVENTION

Diagnostic.

MAIN OUTCOME MEASURES

Click-evoked myogenic potentials were recorded with surface electrodes over each sternocleidomastoid muscle. Latencies and amplitudes of responses were measured.

RESULTS

Vestibular evoked myogenic potentials were absent or decreased in 51% of patients with Meniere disease (n = 22), 39% with vestibular neuritis (n = 9), 77% with acoustic neuroma (n = 48), and 25% with multiple sclerosis (3 of 12 sides of 6 patients). Concerning latency, patients with Meniere disease or vestibular neuritis hardly showed any latency prolongation. Four patients with acoustic neuroma showed prolonged p13; all had large tumors. All patients with multiple sclerosis showed prolonged p13.

CONCLUSION

Prolonged latencies of the VEMP suggest lesions in the retrolabyrinthine, especially in the vestibulospinal tract.

Glycerol affects vestibular evoked myogenic potentials in Meniere's disease

OBJECTIVES

to show that abnormal vestibular evoked myogenic potentials on the sternocleidomastoid muscle (SCM) in patients with unilateral Meniere's disease are caused by endolymphatic hydrops.

SUBJECTS

six normal volunteers and 17 patients with unilateral Meniere's disease were examined.

METHODS

click-evoked myogenic potentials were recorded with surface electrodes over each SCM. Responses evoked by clicks recorded after oral administration of glycerol (1.3 g/kg body weight) were compared with those recorded before administration.

RESULTS

the change rate of the p13-n23 amplitude was calculated. The mean+standard deviation (S.D.) of the change rate was 3.52+14.6% in normal subjects. On the unaffected side of patients the change rates were within the normal range (within the mean+/-2S.D.) in 13 patients, and three ears showed significant decrease. Only one ear showed significant increase. On the affected side, five ears showed significant increase of the amplitude while two ears showed significant decrease after oral administration of glycerol. Effects on evoked myogenic potentials were independent of those on pure tone hearing.

CONCLUSION

vestibular evoked myogenic potentials in some patients with unilateral Meniere's disease were improved by oral administration of glycerol. This result suggests that abnormal vestibular evoked myogenic potentials in patients with unilateral Meniere's disease could result from endolymphatic hydrops.

Sensorineural hearing loss as the initial manifestation of polyarteritis nodosa

A 74-year-old male was referred for the sudden onset of bilateral sudden deafness. The patient had no history of any disease or trauma to the head. Pure tone audiometry revealed bilateral moderate, to severe, sensorineural hearing loss. Auditory brain stem responses (ABRs) showed normal peak and interpeak latencies. These audiological findings suggested that his hearing loss could be attributed to inner ear lesions. However, we felt an alternative explanation for this sudden deafness was likely to exist because the patient also had a month-long fever of unknown origin (FUO) and weight loss of 5 kg/month. Using the criteria of The American College of Rheumatology, we made the diagnosis of polyarteritis nodosa (PAN). Serum MPO-ANCA was positive (x 661). For treatment, the patient was begun on prednisolone and cyclophosphamide. Nine months later, fever, hypertension, nephritis, pneumonitis, and arthritis had completely resolved, the MPO-ANCA became negative (MPO-ANCA < x 10). Furthermore, his hearing improved.

Narrow internal auditory meatus: an idiopathic case confirming the origin and pathway of vestibular evoked myogenic potentials in humans

OBJECTIVE

To confirm the origin and pathway of vestibular evoked myogenic potentials (VEMPs) in humans.

DESIGN

Case study.

SETTING

University hospital.

PATIENT

A patient with a narrow internal auditory meatus (IAM).

MAIN OUTCOME MEASURES

Imaging studies and functional studies concerning the seventh and eighth cranial nerves.

RESULTS

Of the 4 nerves in the IAM, all but the cochlear nerve had normal function and normal courses, despite the pronounced narrowing of the IAM. The facial nerve had a normal diameter, but the vestibular nerves were thinner. Imaging revealed that the cochlear nerve was absent or extremely thinned. Both the cochlea and the cochlear nerve showed no function in the affected ear, although the VEMPs were evoked normally.

CONCLUSION

Our results definitively support the vestibular origin of VEMPs in humans.

The effect of sternocleidomastoid electrode location on vestibular evoked myogenic potential

OBJECTIVE

The purpose of this study was to investigate the effect of a sternocleidomastoid (SCM) electrode array on the vestibular evoked myogenic potential (VEMP) and the most optimal recording site for clinical use.

METHODS

Fifteen normal adults (10 men and 5 women, aged 18 to 38 years) were tested. We placed electrodes at four different locations over the SCM muscle: the upper part of the SCM muscle at the level of mandibular angle, the middle part of the muscle, and immediately above sternal and clavicular origins of the SCM muscle. Sound evoked myogenic potentials in response to monoaurally delivered short tone-bursts (500 Hz at 95 dBnHL, rise/fall time=1 ms and plateau=2 ms) were recorded with surface electrodes over the isometrically contracting SCM muscle.

RESULTS

On the clavicle, the upper and middle parts of SCM from all subjects, air-conducted short tone burst evoked biphasic responses (p13-n23). VEMPs recorded at the upper part of the muscle showed the largest amplitude, followed by that at the middle part. However, the latency of the first peaks (p13-n23) was not constant in the upper part. Recording from the middle part of SCM muscle were more consistent.

CONCLUSION

Our findings suggest that the middle part of the SCM muscle is the optimal location for recording vestibular evoked myogenic potential.

Vestibular function in auditory neuropathy

Auditory neuropathy is characterized by mild-to-moderate pure-tone hearing loss, poor speech discrimination out of proportion with this loss, absent or abnormal auditory brainstem responses and normal outer hair cell function as measured by otoacoustic emissions and cochlear microphonics. We followed three patients in our clinic whom we classified as auditory neuropathy patients. These patients also complained of balance disorders and we report our auditory and vestibular system analyses of these patients. The data presented herein include results of audiometric tests (serial pure-tone audiometry and speech discrimination tests), otoacoustic emissions, auditory-evoked brainstem responses and vestibular function tests (clinical tests of balance, electronystagmography, damped rotation tests and vestibular-evoked myogenic potentials). In all patients, pure-tone audiometry revealed mild-to-moderate sensorineural hearing loss, markedly poor speech discrimination scores and absent auditory-evoked brainstem responses, all in the presence of normal otoacoustic emissions. Balance tests (caloric tests and damped rotation test) were abnormal. Saccades, smooth pursuit eye movements and optokinetic nystagmus were normal in all patients. Neurological and motor system evaluations were normal in all patients. These three auditory neuropathy patients manifest a disorder of cochlear nerve function in the presence of normal outer hair cell activity. They additionally manifest a disorder of the vestibular nerve and its end organs. We conclude that, in patients with isolated auditory neuropathy, the vestibular branch of the VIIIth cranial nerve and its innervated structures may also be affected. We suggest the use of the term "cochlear neuropathy" to characterize those patients with involvement of only the auditory branch of the VIIIth cranial nerve and its innervation.

Vestibular evoked myogenic potentials in patients with spinocerebellar degeneration

To estimate vestibulo-collic reflexes in patients with spinocerebellar degeneration (SCD), vestibular evoked myogenic potentials (VEMPs) were recorded in 16 patients with SCD and in 9 normal subjects. The patients with SCD were classified into three groups: those with olivo-ponto-cerebellar ataxia (OPCA; n = 10); those with cortical cerebellar atrophy (CCA; n = 3); and those with Machado-Joseph disease (MJD; n = 3). While all of the patients with OPCA and CCA showed biphasic responses (p13-n23), 2 of the 3 patients with MJD showed abnormal VEMPs bilaterally. Three sides in these 2 patients showed an absence of VEMPs, and one side showed a remarkably delayed p13. These two patients showed little response in caloric tests. These results suggest that the vestibulo-collic reflex as well as the vestibulo-ocular reflex could be damaged in MJD patients but preserved in OPCA and CCA patients.

Bone-conducted evoked myogenic potentials from the sternocleidomastoid muscle

The aim of this study was to show that bone-conducted clicks and short tone bursts (STBs) can evoke myogenic potentials from the sternocleidomastoid muscle (SCM) and that these responses are of vestibular origin. Evoked potential responses to bone-conducted auditory stimuli were recorded from the SCMs of 20 normal volunteers and from 12 patients with well-defined lesions of the middle or inner ear or the VIIIth cranial nerve. The subjects, who had various labyrinthine and retro-labyrinthine pathologies, included five patients with bilateral profound conductive hearing loss, two with bilateral acoustic neuroma post-total neurectomy and five with bilateral sensorineural hearing loss. Air- and bone-conducted evoked myogenic potentials in response to clicks and STBs were recorded with surface electrodes over each SCM of each subject. In normal subjects, bone- and air-conducted clicks and STBs evoked biphasic responses from the SCM ipsilateral to the stimulated ear. The bone-conducted clicks evoked short-latency vestibular-evoked myogenic potential (VEMP) responses only in young subjects or in subjects with conductive hearing loss. STBs evoked VEMPs with higher amplitude and better waveform morphology than clicks with the same acoustic intensity. Patients with total VIIIth cranial nerve neurectomy showed no responses to air- or bone-conducted click or STB stimuli. Clear VEMP responses were evoked from patients with conductive or sensorineural hearing loss. It is concluded that loud auditory stimuli delivered by bone- as well as air conduction can evoke myogenic potentials from the SCM. These responses seem to be of vestibular origin.

Isolated directional preponderance of caloric nystagmus: I. Clinical significance

OBJECTIVES

To determine the clinical significance of an isolated directional preponderance (DP) on bithermal caloric testing. An isolated caloric DP was defined as a DP, calculated according to the standard Jongkees formula, of > or = 40%, with a spontaneous nystagmus (SN) in darkness of < or = 2 degrees/s and a canal paresis (unilateral weakness) of < or = 25%.

STUDY DESIGN

A retrospective analysis of all 15,542 bithermal caloric tests performed in the authors' department in the previous 10 years to identify all tests with an isolated DP of > or = 40%. This was followed by a review of the clinical data on the 144 patients identified with such a result and then by a telephone or postal follow-up study of these patients. The study group eventually comprised 114 patients; these were patients in whom a clinical diagnosis could be made at the time the caloric test was done, or who responded to requests for follow-up information. The 34 patients in whom a clinical diagnosis could not be made at the time of the caloric test, and who did not respond to requests for follow-up information, were excluded.

STUDY SETTING

A balance disorders clinic in a tertiary referral hospital.

INTERVENTION

All patients underwent standard bithermal caloric testing. Some of the patients also underwent rotational testing.

OUTCOME MEASURES

A clinical diagnosis for the cause of the isolated DP, made either at the time of the caloric test or on the basis of information supplied at follow-up by the patient or by the referring physician.

RESULTS

Of 114 patients, 39 had benign paroxysmal positioning vertigo, 14 had Ménière's disease, and 5 had migrainous vertigo. Five patients had central nervous system (CNS) disorders, and this was clinically apparent at the time of the caloric test in 4, so that only 1 patient with an isolated DP developed evidence of a CNS disorder after the caloric test was done. In the other 54 patients, no definite diagnosis could be made, but 41 of these 54 were either completely well or much better at follow-up.

CONCLUSIONS

An isolated DP on caloric testing is usually a transient, benign disorder. About half the patients with an isolated DP have either Ménière's disease or benign paroxysmal positioning vertigo; in most of the other half, no definite diagnosis is made but most of these patients will do well. Only approximately 5% have a CNS lesion and in almost all this is apparent at the time the caloric test is done. In a relapsing-remitting peripheral vestibular disorder such as benign paroxysmal positioning vertigo or Ménière's disease, the mechanism of an isolated DP could be enhanced dynamic gain of ipsilesional medial vestibular nucleus neurons, perhaps as a result of intermittent hyperfunction of primary semicircular canal vestibular afferents. The authors postulate that an isolated DP reflects a gain asymmetry between neurons in the medial vestibular nucleus on either side, caused either by increased sensitivity on one side or by reduced sensitivity on the other, perhaps as an adaptive change in response to abnormal input. In an accompanying article, the authors implement a realistic neural network model in which it is possible to simulate an isolated DP by adjusting the dynamic sensitivity of type 1 medial vestibular nucleus neurons on one side or of type 2 medial vestibular nucleus neurons on the other.

Tone burst-evoked myogenic potentials in human neck flexor and extensor

Vestibular evoked myogenic potential (VEMP) has been proposed to be a manifestation of sacculocollic reflex. In a recent study using intracellular recording from neck flexor and extensor motoneurons, the neuronal connections and pathways underlying sacculocollic reflexes were determined in cats. The results showed that sacculocollic reflex displayed inhibitory connection to bilateral neck flexors and excitatory connection to bilateral neck extensors. A total of 16 normal young adults were tested with bilateral recordings of sternocleidomastoid (SCM) and splenius capitis (SC) muscles by acoustic stimulus of 500 Hz short tone burst. The results revealed that polarity of the wave I/II of VEMP on SC was the reverse of that on SCM. This implied that VEMP from ipsilateral SCM showed inhibitory neural activity; whereas VEMP from ipsilateral SC was an excitatory response. Using this non-invasive technique, the sacculocollic reflexes in human neck flexor and extensor were studied. The results in humans were consistent with the previous findings in cats.

Periodic alternating nystagmus and congenital nystagmus: similarities in possibly inherited cases

In this paper, 2 patients, a daughter with periodic alternating nystagmus and a mother with congenital fixation nystagmus, are presented, and the similarities of the two disorders are discussed, not only in the eye movements, but also in their underlying abnormalities. The literature was reviewed, and the link between periodic alternating and congenital fixation nystagmus, which had been suggested based on circumstantial evidence, may be confirmed by our cases. The possible evidence of inheritance suggests that the two disorders share common abnormalities in visual processing.

Auditory brainstem responses, electrocochleograms, and cochlear microphonics in the myelin deficient mutant hamster 'bt'

Electrophysiological studies of the auditory pathway were performed on the mutant hamster 'bt' which is known to have myelin deficiencies in the central nervous system. Auditory brainstem responses (ABRs), electrocochleograms (EcochGs), and cochlear microphonics (CMs) were recorded. ABRs in 'bt' demonstrated markedly transformed waveforms with significantly prolonged latencies. EcochG in 'bt' showed significantly prolonged N1 latencies of the compound action potentials (CAPs) while 'bt' showed normal CMs. The myelin deficient mutant hamster 'bt' may have myelin deficiencies not only in the brainstem auditory pathway but also in the cochlear nerve.

Short tone burst-evoked myogenic potentials on the sternocleidomastoid muscle: are these potentials also of vestibular origin?

OBJECTIVES

To show that short tone bursts (STBs) evoke myogenic potentials from the sternocleidomastoid muscle (SCM) that are of vestibular origin.

DESIGN

Evoked potential activity was recorded from the SCMs of normal volunteers and from patients with vestibulocochlear disorders.

SETTING

This outpatient study was conducted at the Department of Otolaryngology, University of Tokyo, Tokyo, Japan.

SUBJECTS

Nine normal volunteers and 30 patients (34 affected ears) with vestibulocochlear disorders were examined.

INTERVENTION

Diagnostic.

OUTCOME MEASURES

Sound-evoked myogenic potentials in response to STBs were recorded with surface electrodes over each SCM. Responses evoked by STBs in patients were compared with responses evoked by clicks.

RESULTS

In all normal subjects, STBs (0.5, 1, and 2 kHz) evoked biphasic responses on the SCM ipsilateral to the stimulated ear; the same was true for clicks. Short tone bursts of 0.5 kHz evoked the largest responses, while STBs of 2 kHz evoked the smallest. In patients with vestibulocochlear disorders, responses to STBs of 0.5 kHz were similar to responses evoked by clicks. Thirty (88%) of the 34 affected ears demonstrated the same results with 0.5-kHz STBs and with clicks. Responses were present in patients with total or near-total hearing loss and intact vestibular function. Conversely, patients with preserved hearing but with absent or severely decreased vestibular function had absent or significantly decreased myogenic potentials evoked by STBs.

CONCLUSIONS

Short tone bursts as well as clicks can evoke myogenic potentials from the SCM. Myogenic potentials evoked by STBs are also probably of vestibular origin.

Vestibular evoked myogenic potentials in acoustic tumor patients with normal auditory brainstem responses

In order to clarify the utility of the vestibular evoked myogenic potential (VEMP) in detecting acoustic tumors, we report two patients who were found to have normal auditory brainstem responses (ABRs) and abnormal VEMPs. To record VEMPs, electromyographic responses to brief loud clicks (0.1 ms at 95 dBnHL) were amplified and averaged on the sternocleidomastoid muscle ipsilateral to the stimulated side. The stimulation rate was 5 Hz and the analysis time 50 ms. The first case was a 54-year-old woman in whom VEMPs were absent on the affected side while caloric tests and ABRs were normal. The second case was a 58-year-old woman whose VEMPs were absent on the affected side while caloric tests revealed a 22% canal paresis and normal ABRs. These results and previous studies suggested that the VEMP could reflect a function different from those evaluated by the ABR or the caloric test. We concluded that the VEMP can provide useful information in diagnosing acoustic tumors.

Vestibular evoked myogenic potentials in patients with bilateral profound hearing loss

We report vestibular evoked myogenic potentials (VEMPs) in 3 patients with bilateral profound hearing loss in order to confirm that they are not of cochlear origin. All of the 3 patients (31-year-old man, 67-year-old man and 47-year-old woman) had bilateral profound hearing loss. They were diagnosed as having congenital hearing loss, bilateral Ménière's disease and inner ear syphilis. Their pure-tone hearing ranged from 81 dB HL to nearly total hearing loss. Stimulation by click (95 dB nHL) evoked biphasic myogenic responses (p13-n23) on the sternocleidomastoid muscle ipsilateral to the stimulated ear. The ear in which the stimulation did not evoke biphasic myogenic responses did not have a caloric response either. These results suggested that VEMPs are not likely of cochlear origin but of vestibular origin.

The effect of click repetition rate on vestibular evoked myogenic potential

Vestibular evoked myogenic potentials (VEMPs) generated by click stimulation and recorded on the sternocleidomastoid muscle have been used as a test of vestibular reflexes. Various parameters of the stimulus and recording setting have been studied. However, the influence of stimulation repetition rate of VEMPs and the most optimal stimulation rate for clinical use have not yet been defined. Each ear of 12 normal adults was tested at five different click stimulation rates (1 Hz, 5 Hz, 10 Hz, 15 Hz and 20 Hz) in random order. VEMP responses were evident in all 24 ears stimulated with 1 Hz, 5 Hz and 10 Hz. One ear was void of response at 15 Hz stimulation and nine ears at 20 Hz stimulation. The relative amplitude or the rank of amplitude in individual ears was higher at 1 Hz and 5 Hz stimulation, progressively decreasing as the stimulation rate increased. Comparisons of p13 and n23 latencies showed no difference among five stimulation rates, but variance was greatest at 20 Hz stimulation and smallest at 1 Hz. VEMPs generated at lower stimulation repetition rate seemed to be more marked and constant. However, with regard to examination time and patient compliance, a 5 Hz stimulus is advisable if both short examination time and higher signal/noise ratio are required.

Vestibular evoked myogenic potentials in patients with acoustic neuromas

BACKGROUND

To diagnose acoustic neuromas (ANs), the auditory brainstem response test and the caloric test have been used in addition to magnetic resonance imaging. The auditory brainstem response and the caloric tests mainly reflect functions of the auditory pathway, ie, the cochlear nerve and the superior vestibular nerve, respectively. Because the vestibular evoked myogenic potential (VEMP) has been thought to originate in the inferior vestibular nerve, we hypothesized that the VEMP could provide different information from the auditory brainstem response and the caloric test and that it could be helpful in diagnosing ANs. In other words, we hypothesized that the VEMP could provide information concerning inferior vestibular nerve involvement in patients with ANs.

OBJECTIVE

To find out if the VEMP could be useful in classifying ANs according to the involved nerves.

DESIGN

We reviewed preoperative clinical tests, including VEMPs, in 21 patients (8 men, 13 women) with ANs confirmed surgically and histopathologically, comparing them with VEMPs in 8 normal subjects (5 men, 3 women).

RESULTS

Whereas the first positive-negative peak of the VEMP, P13-N23, was ipsilaterally present on stimulation of the unaffected side in all patients with ANs and both sides in all normal subjects, it was absent on the affected side in 15 patients (71%) and significantly decreased in amplitude in 2 patients (9%). Thus, 17 (80%) of the 21 patients showed abnormal VEMPs. Three patients had abnormal VEMPs although they had normal caloric responses. Three patients had abnormal caloric responses although they had normal VEMPs.

CONCLUSION

These results suggest that the VEMP could be useful for the diagnosis of AN, especially for classifying ANs according to the involved nerves.

Bilateral pseudo-internuclear ophthalmoplegia in myasthenia gravis

A 38-year-old male with bilateral pseudo-internuclear ophthalmoplegia (-INO) in myasthenia that could have been misdiagnosed as INO in multiple sclerosis is reported. He experienced fluctuating symptoms including double vision, imbalance, and tinnitus. His eye movements simulated bilateral INO, with a downshoot in abduction. After thymectomy, his eye movements became normal. From our case and a review of the literature, we propose that ptosis, downshoot, and fatigability are likely to be signs of pseudo-INO in myasthenia, whereas an impaired vertical smooth pursuit is unlikely. Dissociated nystagmus and monocular overshoot might be the results of central compensation.

Perineural Spread of Facial Squamous Cell Carcinoma to the Vestibulocochlear Nerve

Perineural spread of facial squamous cell carcinoma (SCC) is a well-recognized cause of trigeminal and of facial nerve palsies. 1 Vestibulocochlear nerve involvement by perineural spread has not been convincingly demonstrated. Here we report a patient with perineural spread of facial SCC not only to the trigeminal and facial nerves but also to the ipsilateral vestibulocochlear nerve. The anatomic and pathophysiologic basis of this spread is discussed.