VIN protocol
VIN testing was completed using the V.VIB 3 F Stimulator (Synapsis, Inc., Marseille, France). This stimulator is a mechanical off-axis rotating vibrator with a vibration amplitude of 1 mm and a cylindrical contact surface 2 cm in diameter.
VIN testing was applied to the mastoid process and in the lower part of the SCM muscle. Growing stimulus frequencies of 30, 60, and 100 Hz were applied for 10 s each. Rest periods of 30 s were used between each stimulus application.
The maximum velocity of the slow phase (MVSP) components of nystagmus evoked by each stimulation was determined with a 2D video-based system (Ulmer VNG, v. 1.4, SYNAPSIS, Marseille, France).