Masaki Matsuzaki

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

Abstract 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.

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 Menieres disease are caused by endolymphatic hydrops. SUBJECTS six normal volunteers and 17 patients with unilateral Menieres 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 Menieres disease were improved by oral administration of glycerol. This result suggests that abnormal vestibular evoked myogenic potentials in patients with unilateral Menieres disease could result from endolymphatic hydrops.

Risk factors for neurological complications after acoustic neurinoma radiosurgery: refinement from further experiences

PURPOSE Further actuarial analyses of neurological complications were performed on a larger population treated by stereotactic radiosurgery at our institution, to establish the optimal treatment parameters. METHODS AND MATERIALS Between June 1990 and September 1998, 138 patients with acoustic neurinomas underwent stereotactic radiosurgery at Tokyo University Hospital. Of these, 125 patients who received medical follow-up for 6 months or more entered the present study. Patient ages ranged from 13 to 77 years (median, 53 years). Average tumor diameter ranged from 6.7 to 25.4 mm (mean, 13. 9 mm). Maximum tumor doses ranged from 20 to 40 Gy (mean, 29.8 Gy) and peripheral doses from 12 to 25 Gy (mean, 15.4 Gy). One to 12 isocenters were used (median, 4). Follow-up period ranged from 6 to 104 months (median, 37 months). The potential risk factors for neurological complications were analyzed by two univariate and one multivariate actuarial analyses. Neurological complications examined include hearing loss, facial palsy, and trigeminal nerve dysfunction. Variables included in the analyses were four demographic variables, two variables concerning tumor dimensions, and four variables concerning treatment parameters. A variable with significant p values (p < 0.05) on all three actuarial analyses was considered a risk factor. RESULTS The variables that had significant correlation to increasing the risk for each neurological complication were: Neurofibromatosis Type 2 (NF2) for both total hearing loss and pure tone threshold (PTA) elevation; history of prior surgical resection, tumor size, and the peripheral tumor dose for facial palsy; and the peripheral tumor dose and gender (being female) for trigeminal neuropathy. In facial palsies caused by radiosurgery, discrepancy between the course of palsy and electrophysiological responses was noted. CONCLUSION Risk factors for neurological complications seem to have been almost established, without large differences between institutions treating a large number of patients by radiosurgery. Radiosurgical doses and tumor dimensions were considered the two important risk factors for the 7th and 5th nerve injuries. Neurofibromatosis Type 2 was an important factor for hearing loss.

Vestibular Evoked Myogenic Potentials in Patients with Idiopathic Bilateral Vestibulopathy

Idiopathic bilateral vestibulopathy (IBV) is an acquired bilateral peripheral vestibular disorder of unknown cause. Three patients diagnosed as IBV by neuro-otological examination were reported. They underwent vestibular evoked myogenic potential (VEMP) testing which reflects the functionality of the sacculo-collic pathway. As a result, 2 of the 3 patients showed bilateral absence of VEMPs and one showed unilateral absence. The VEMPs of the 3 patients revealed that IBV affects not only the superior but also the inferior vestibular nerve systems. As previously reported in the cases of vestibular neuritis, VEMP could be useful for classifying IBV according to the function of the inferior vestibular nerve.

Vestibular Evoked MyogenicPotentials 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.

Lesion site in idiopathic bilateral vestibulopathy: A galvanic vestibular-evoked myogenic potential study

Conclusion The result suggests that patients with idiopathic bilateral vestibulopathy may have nerve lesions when the inferior nerve system is affected, while the inferior vestibular nerve system may be spared. Objective To clarify the lesion site in idiopathic bilateral vestibulopathy, an acquired bilateral vestibulopathy of unknown cause. Material and methods Two 75-year-old males diagnosed with idiopathic bilateral vestibulopathy were enrolled. Both showed absent or highly decreased responses on the caloric test on both sides. They underwent vestibular-evoked myogenic potential (VEMP) testing by means of acoustical and electrical stimulation. As acoustic stimulation, 95 dB nHL clicks and short tone bursts (500 Hz) were presented, while 3 mA (1 ms) short-duration galvanic stimuli were presented as electrical stimulation. Responses were recorded on the sternocleidomastoid muscles. Results Both patients showed unilateral absence of VEMPs with both acoustic and short-duration galvanic stimuli.

Vestibular Evoked Myogenic Potentials in Ipsilateral Delayed Endolymphatic Hydrops

We recorded vestibular evoked myogenic potentials (VEMPs) in 12 patients diagnosed as having ipsilateral delayed endolymphatic hydrops (DEH). Seventy-five percent (9/12) of the patients showed decreased or absent VEMPs in the affected ears. Almost all patients had normal VEMPs in the unaffected ears. In addition, in 4 patients, VEMPs were recorded before and 3 h after oral glycerol administration (1.3 g/kg body weight). VEMPs improved after glycerol administration in 2 of the 3 patients whose VEMPs had been abnormal in the affected ears before glycerol administration. None of the 4 patients presented significant changes in VEMPs in the unaffected ears after glycerol administration. Improvement of VEMPs after glycerol administration confirmed the existence of endolymphatic hydrops in patients with ipsilateral DEH. In conclusion, VEMPs are useful to evaluate the function of otolith organs in patients with ipsilateral DEH, and the glycerol test using VEMPs may be useful to detect endolymphatic hydrops in ipsilateral DEH.

Vestibular evoked myogenic potentials in patients with contralateral delayed endolymphatic hydrops.

Abstract We studied vestibular evoked myogenic potentials (VEMPs) in nine patients with unilateral profound hearing loss followed by contralateral delayed hearing fluctuation and episodic vertigo. This condition has been called contralateral delayed endolymphatic hydrops. Five of nine ears with profound hearing loss (56%) showed an absence of VEMPs. One ear (11%) showed decreased responses, and three ears (33%) had normal responses. Of the ears with fluctuation of hearing, six (67%) showed an absence of responses, and three ears (33%) showed normal responses. In four patients we recorded VEMPs before and after oral administration of glycerol. Three hours after glycerol administration, two of four ears with fluctuating hearing loss showed the appearance of VEMPs although there was an absence of VEMPs before glycerol administration. These results suggested that saccular dysfunction could exist not only in the ears with profound hearing loss but also in ears with fluctuating hearing loss and that saccular endolymphatic hydrops could exist in the ears with fluctuating hearing loss. “Contralateral delayed endolymphatic hydrops” might be an appropriate term.

Click- and Short Tone Burst-evoked Myogenic Potentials in Cerebellopontine Angle Tumors

We report results of vestibular-evoked myogenic potentials (VEMPs) in patients with cerebellopontine angle tumors and compare results obtained using clicks with those obtained using 500 Hz short tone bursts (STB). We reviewed the records of 87 patients with cerebellopontine angle tumors. Clicks (0.1 ms, 95 dB nHL) were presented to all patients and STB (500 Hz, rise/fall time 1 ms, plateau time 2 ms, 95 dB nHL) were presented to 27 patients. Click-evoked VEMPs were abnormal in 69/87 patients (79%; no response in 55 patients, decreased response in 14 patients, normal response in 18 patients). STB-evoked VEMPs were abnormal in 22/27 patients (82%; no response in 18 patients, decreased response in 4 patients, normal response in 5 patients). Click- and STB-evoked VEMPs were identical in 23/27 patients (85%). Two patients showed normal STB-evoked VEMPs and decreased click-evoked VEMPs, and 2 patients showed decreased STB-evoked VEMPs and absent click-evoked VEMPs. These results confirm our previous study in a small number of patients. Vestibular afferents seem to respond better to 500 Hz STBs than to clicks.We report results of vestibular-evoked myogenic potentials (VEMPs) in patients with cerebellopontine angle tumors and compare results obtained using clicks with those obtained using 500 Hz short tone bursts (STB). We reviewed the records of 87 patients with cerebellopontine angle tumors. Clicks (0.1 ms, 95 dB nHL) were presented to all patients and STB (500 Hz, rise/fall time 1 ms, plateau time 2 ms, 95 dB nHL) were presented to 27 patients. Click-evoked VEMPs were abnormal in 69/87 patients (79%; no response in 55 patients, decreased response in 14 patients, normal response in 18 patients). STB-evoked VEMPs were abnormal in 22/27 patients (82%; no response in 18 patients, decreased response in 4 patients, normal response in 5 patients). Click- and STB-evoked VEMPs were identical in 23/27 patients (85%). Two patients showed normal STB-evoked VEMPs and decreased click- evoked VEMPs, and 2 patients showed decreased STB-evoked VEMPs and absent click- evoked VEMPs. These results confirm our previous study in a small number of patients. Vestibular afferents seem to respond better to 500 Hz STBs than to clicks.

Click-evoked potentials on the neck of the guinea pig.

Vestibulocollic reflex in humans is called vestibular evoked myogenic potential. To try to establish an animal model of the acoustically evoked vestibulocollic reflex, 18 guinea pigs were used in this study. Eight of the 18 guinea pigs received intramuscular injection of amikacin for 18 days (450 mg/kg/day) before recording to destroy the cochlea pharmacologically. Under general anesthesia with intraperitoneal injection of pentobarbital sodium (40 mg/kg body weight), auditory brainstem responses (ABRs) were recorded. Then potentials on the neck evoked by loud clicks were recorded on the pre-vertebral muscle or on the spinal cord at the level of third cervical vertebral bone using a silver-ball electrode. As a result, a negative peak (NP) with a latency of 6 approximately 8 ms was observed on the neck muscle or on the spinal cord in the control group. The thresholds of the NP were 90-100 dB above those of ABRs. The NP was also observed in the amikacin-administered group using clicks with the same intensity as that for the control group, while the ABR thresholds were highly elevated. These results are in agreement with a vestibular origin of the NP potential.