Vestibular evoked myogenic potentials of undiagnosed dizziness.

OBJECTIVE: Recording of vestibular evoked myogenic potentials (VEMP) can facilitate the evaluation of otolith function. The dizziness caused by otolith lesions is not completely understood. To clarify which symptoms of dizziness originate from the otolith organs, we examined the relationship between symptoms and VEMP results in patients with undiagnosed dizziness. METHODS: The subjects were 18 patients with undiagnosed dizziness aged less than 40 years who underwent VEMP examination. The VEMP results were evaluated using the interaural ratio of p13-n23 amplitude. RESULTS: Abnormal VEMP results were obtained in five of seven patients who experienced a sensation of falling (p=0.013), in none of the three patients who experienced a swaying sensation (p>0.05), and in one of eight patients who experienced a floating sensation (p>0.05). Five of six patients with abnormal VEMP results complained of disequilibrium lasting a few seconds. CONCLUSIONS: Dizziness with a sensation of falling lasting for a few seconds was related to abnormal VEMP results, suggesting that it resulted from saccular dysfunction. VEMP examination may be considered a useful modality in the diagnosis of dizziness of unknown origin.

Preliminary study on vestibular-evoked myogenic potential induced by bone-conducted stimuli.

OBJECTIVE: To study the relationship between vestibular-evoked myogenic potential evoked by air-conducted stimuli (A-VEMP) and those evoked by bone-conducted stimuli (B-VEMP). STUDY DESIGN: Prospective study. SETTING: University Hospital. PATIENTS: To determine the optimum stimulus conditions for B-VEMP, 40 ears of 20 healthy volunteers were used. To compare results of A-VEMP and B-VEMP, 60 ears of 30 healthy volunteers and 70 ears of 35 patients with unilateral vestibular disorder without conductive hearing loss were used. MAIN OUTCOME MEASURE: A-VEMP and B-VEMP were measured. Both examinations involved evaluation of the interaural ratio (IAR) of the p13-n23 peak-to-peak amplitude. To compare the relationship between A-VEMP and B-VEMP in healthy subjects and patients with unilateral vestibular disorder. RESULTS: The optimum stimulus for B-VEMP seemed to be a tone-burst sound with 8-ms duration at 250 Hz. In all healthy subjects, both A-VEMP and B-VEMP could be recorded. The mean IAR of B-VEMP (0.5 +/- 21.0%) was not significantly different from that of A-VEMP (0.2 +/- 19.4%). In patients with unilateral vestibular disorder, B-VEMP could not be detected in 10 ears in which A-VEMP also could not be detected. The IAR of A-VEMP was strongly correlated with that of B-VEMP (correlation coefficient, 0.98). CONCLUSION: The results of B-VEMP were almost the same as those for A-VEMP, at least, for patients without conductive hearing loss.

Frequency dynamics shift of vestibular evoked myogenic potentials in patients with endolymphatic hydrops.

OBJECTIVE: To measure the frequency dynamics of the vestibular evoked myogenic potential in patients with endolymphatic hydrops. STUDY DESIGN: A prospective study. SETTING: A university hospital. SUBJECTS: The endolymphatic hydrops group consisted of 28 affected ears of patients with definite unilateral Ménière's disease and a control group of 36 ears of 20 healthy volunteers. INTERVENTIONS: Vestibular evoked myogenic potentials generated by tone bursts at 250, 500, 700, 1,000, 1,500, 2,000, and 4,000 Hz were measured in both groups. Vestibular evoked myogenic potentials were also measured after furosemide administration in six patients in the endolymphatic hydrops group. MAIN OUTCOME MEASURE: The frequency sensitivity of vestibular evoked myogenic potential, as evaluated by p13-n23 normalized amplitude. RESULTS: Peak amplitudes were noted at 500 Hz in the control group and at 1,000 Hz in the endolymphatic hydrops group. After furosemide loading, peak amplitude shifted to a lower frequency in four of six ears. CONCLUSION: The peak amplitude of vestibular evoked myogenic potentials in the endolymphatic hydrops group was at a higher frequency than in the control group. The frequency of the saccule (nu) should be proportional to radical(tau/sigma), where tau is the tension of membrane and sigma is its density. We advocate the hypothesis that the shift in frequency dynamics of vestibular evoked myogenic potential in patients with endolymphatic hydrops originates from the morphologic features of the saccule, analogous to an expanded balloon.

Three cases of cochleosaccular endolymphatic hydrops without vertigo revealed by furosemide-loading vestibular evoked myogenic potential test.

OBJECTIVE: To describe possible cases of cochleosaccular endolymphatic hydrops without vertigo. STUDY DESIGN: Retrospective case report. SETTING: University hospital. PATIENTS: Three patients with possible cochleosaccular hydrops without vertigo were studied. The basis of diagnosis was positive result of the furosemide-loading vestibular evoked myogenic potential test, no canal paresis in the caloric test, and recurrent cochlear symptoms or fluctuating low-tone hearing loss. CASE REPORT: In case 1, a 47-year-old woman had recurrent left aural fullness and tinnitus and a few weeks later complained of a floating sensation and could not stand up. The furosemide-loading vestibular evoked myogenic potential test showed a positive result in the left ear. In case 2, a 24-year-old woman complained of a backward falling sensation lasting several seconds; subsequently, a severe floating sensation persisted and she could not stand up for several days. Audiography showed fluctuating low-tone hearing loss in the left ear, and the furosemide-loading vestibular evoked myogenic potential test showed a positive result. In case 3, a 41-year-old woman had a floating sensation while walking and subsequently complained of tinnitus in the left ear. She could not stand up because of a severe floating sensation and, moreover, complained of a sudden falling sensation lasting for several seconds. The furosemide-loading vestibular evoked myogenic potential test indicated a positive result in the left ear. CONCLUSIONS: The patients in cases 2 and 3 complained of a short-lasting sensation of falling down. Severe disequilibrium that prohibited standing up was noted in all cases. It was suggested that these symptoms were caused by saccular hydrops.

Furosemide loading vestibular evoked myogenic potential for unilateral Ménière's disease.

OBJECTIVE: To investigate whether endolymphatic hydrops in Ménière's Disease could be diagnosed by comparing vestibular evoked myogenic potential (VEMP) before and after furosemide administration (F-VEMP). STUDY DESIGN: Retrospective study. SETTING: University hospital. INTERVENTION: Furosemide administration. PATIENTS: Twenty-five affected ears of patients with unilateral Ménière's Disease were studied. The patients had received confirmed diagnoses Ménière's Disease; thus, the presence of endolymphatic hydrops was suggested. For the control, 22 ears of 11 normal healthy volunteers who had never had vertigo or hearing disturbance were used. MAIN OUTCOME MEASURE: The amplitude of the p13-n23 biphasic wave before and after furosemide administration. RESULTS: The amplitude of the p13-n23 biphasic wave was significantly enlarged in 7 of 18 cases in which it could be detected before diuretic loading. The biphasic waves appeared after diuretic loading in 3 of 7 cases in which it could not be recorded before loading. Thus, the positive ratio of F-VEMP for unilateral Ménière's Disease was considered to be 40% (10 of 25). The ratio was similar to that of the conventional examinations for endolymphatic hydrops such as the glycerol test, furosemide test, and electrocochleogram. CONCLUSION: The F-VEMP test may be useful in the diagnosis of endolymphatic hydrops.