Test-retest reliability of vibration-induced nystagmus in peripheral dizzy patients

The purpose of this study was to analyze test-retest reliability of vibration-induced nystagmus (VIN) in dizzy patients. Fifty-two consecutive patients with positive eye movements induced by vibration at all four different stimulation sites were enrolled. Evaluation of VIN was repeated in 2 separate sessions, 30 minutes apart. Maximum slow-phase eye velocities at different sites from the first and second sessions were assessed via the intraclass correlation coefficient (ICC) and the Pearson correlation coefficient. The incidence of directional changing of evoked nystagmus and the abnormal rates were also evaluated. Excellent reliability with ICC values ranging from 0.89-0.98 and substantial-to-excellent correlation was obtained for the maximum slow-phase eye velocities at different sites. The incidence of directional changes of evoked nystagmus was 0%-4% at each stimulation site. Forty-three patients (83%) had abnormal results in the first session and 41 patients (79%) had abnormal results in the second session. Overall, the direction and maximum slow-phase eye velocities of VIN for different stimulation sites had excellent test-retest reliability. The VIN test is a reliable test for detecting vestibular imbalance in evaluating a dizzy patient.