PR-6. VIBRATION-INDUCED NYSTAGMUS IN ACUTE NON-FLUCTUATING UNILATERAL PERIPHERAL VESTIBULOPATHY

Ja-Won Koo, Il Joon Moon, Ji Soo Kim (Seoul National University College of Medicine, Korea)

 

Objectives: Vibration-induce nystagmus (VIN) is clearly documented in severe unilateral peripheral vestibular loss but the diagnostic value of VIN is still controversial. We tried to characterize VIN in patients with non-fluctuating unilateral peripheral vestibulopathy and in healthy individuals.

Methods: 40 patients with acute peripheral vestibulopathy were included. Patients assumed fluctuating or slowly aggravating vestibulopathy were excluded. Vibrator (100Hz) was applied to one mastoid for 10 seconds and then moved to the contralateral side. Slow phase velocity of spontaneous nystagmus, VIN and immediate post head shaking nystagmus (pHSN) was measured using videonystagmography (VNG) system. After subtracting the amount of spontaneous nystagmus, the direction and the intensity of horizontal component of corrected VIN (cVIN) and immediate corrected post-head shaking nystagmus (cpHSN) were obtained. Both induced nystagmus were analyzed according to the disease duration, canal paresis (CP) and results of vestibular evoked myogenic potentials (VEMP). Age matched 25 healthy volunteers who showed normal caloric response and VEMP were included for control.

Results: VIN was present in 7 out of 25 healthy individuals (28%). Of the 40 patients, cVIN was present in 31 (78%) patients at both side and in 6 (15%) patients at one side vibration. The direction of VIN was mostly contralesional side except 1 patient who showed VIN at only one side. The intensity of cVIN was more than 5 ^o/sec in 32 (80%). cpHSN was present in 31 (78%) patients and the direction was contralesional in 26 and ipsilesional in 5. The intensity of cVIN was correlated with CP (r=0.34, p<0.05), while that of cpHSN showed no significant correlation with CP. However, the intensity of cVIN was not correlated with the disease duration, while that of cpHSN showed strong negative correlation with the disease duration (r=-0.671, p<0.001).

Conclusions: The intensity of VIN seems to depend on the extent of peripheral vestibular loss and reflect the side difference of peripheral vestibular excitability, while that of pHSN seems to reflect current status of compensation. VIN may provide valuable information regarding the presence and lateralization of vestibular loss if used combined with head shaking maneuver and head thrust test.

 

* Contact person email: jwkoo99@snu.ac.kr