[Clinical significance of vibration-induced nystagmus in patients with unilateral peripheral vestibular disorders].

OBJECTIVE

To clarify the clinical significance of vibration-induced nystagmus (VIN) and to calculate the sensitivity and the specificity of the vibration test.

METHODS

One hundred and twelve patients with unilateral peripheral vestibular disorders and 30 normal subjects were enrolled into this study. However, patients with spontaneous nystagmus were excluded. Vibratory stimuli (approximately 92Hz) were presented to the mastoids and the forehead. Patients and normal subjects also underwent head shaking testing and caloric testing.

RESULTS

Of the 112 patients, 91 (81%) showed VIN which were mainly horizontal. VIN was more frequently evoked on the mastoids than on the forehead. In the majority of patients (76 cases), the direction of VIN was toward the healthy side, whereas patients with Meniere's disease (15 cases), showed nystagmus toward the affected side. None of 30 normal subjects showed VIN. Whereas, HSN was found in 70 (63%) patients and 9 (30%) in normal subjects. Of 112 patients, 10 showed a canal paresis (CP) value of caloric test less than 25% ,while 32 with a CP value between 25% and 40%, 48 with a CP value between 40% and 70%, and 22 with a CP value more than 70%. It is notable that with increasing canal paresis value on caloric testing, VIN was more likely to be evoked.

CONCLUSIONS

VIN testing is a simple, non-invasive and well-tolerated clinical test that indicates unilateral peripheral vestibular dysfunction. VIN testing had greater sensitivity and the specificity than HSN testing in the diagnosis of unilateral peripheral vestibular disorders.