Implication of vibration induced nystagmus in Meniere's disease.

Conclusion: The incidence of ipsilesional beating vibration induced nystagmus (VIN) is significantly higher in Meniere's disease (MD) with lower canal paresis (CP) group on caloric test and the intensity of VIN shows significant positive correlation with CP. Considering previous reports showing predominant loss of type II hair cells in MD and discrepancy of the results between caloric test and head thrust test in MD patients, VIN may provide valuable information regarding the functional reservoir of vestibular type II hair cells in MD.
Objectives: Clinical presentation of MD is dynamic and nystagmus changes phase to phase, which is attributed to the recovery process in addition to central compensation after active vertigo attack of MD. VIN has been shown to reflect the side difference of peripheral vestibular excitability and is well correlated with the severity of caloric weakness in vestibular neuritis. Aim of this study was to compare the intensity and the direction of VIN with CP in unilateral MD.
Materials and Methods: 52 patients with unilateral definite MD on AAO-HNS guideline (1995) were included. Auditory and vestibular function tests including caloric test, post-head shaking nystagmus (HSN) and VIN were evaluated during symptom free period and cases with spontaneous nystagmus were excluded. Vibratory stimuli (100 Hz) were applied to either mastoid alternatively. Eye movement was recorded using video nystagmography system. The horizontal component of VIN was compared with HSN and caloric test.
Results: 37 patients (71%) showed VIN. VIN to ipsilesional side was in 10 and to contralesional side in 27. In patients with CP over 43% (N =23), 2 beated to ipsilesional side, 17 to contralesional side and 4 showed no VIN. In patients with CP of less than 43% (N =29), 8 beated to ipsilesional side, 10 to contralesional side and 11 showed no VIN (p<0.05). 33 patients (63%) showed HSN and 24 patients of them (72%) showed contralesional nystagmus. The intensity of VIN shows significant positive correlation with the degree of CP on caloric test (Spearman's rho =0.340, p<0.05).