Increased Perception of Head Tilt to Galvanic Vestibular Stimulation Correlates to Motion Sickness Susceptibility in Vestibular Migraine.

Abstract

Vestibular migraine is associated with vertigo, persistent swaying, tilting, and disorientation, which suggests a heightened sensitivity of the neural mechanisms subserving spatial orientation. Whether a heightened sense of motion to vestibular stimulation in vestibular migraine is associated with sensitivity to visual motion (visual dependency) or physical motion (motion sickness susceptibility) is unclear. The aim of this study was to explore whether a heightened sense of self-motion sensitivity in vestibular migraine is associated with visual dependency or motion sickness susceptibility. This is a prospective cross-over study. Fifteen participants with vestibular migraine and 20 healthy controls (all right handed) were included in this study. In the main experiment, participants were asked to align a rod to the perceived head position. Head tilt was generated by DC galvanic vestibular stimulation at 1 mA to produce head tilts to the right (left anodal/right cathodal stimulation, LA/RC) or left (right anodal/left cathodal, RA/LC). The perception of head tilt was measured in a dark room using laptop software that allowed participants to turn an illuminated rod to any angle about the midpoint. Participants were instructed to align the rod to the perceived head position before and during galvanic stimulation and the line angle was saved. Head position was objectively monitored with an ultrasound motion system. After completing the perceptual test, visual dependency was measured with a static and rotating background and the Motion Sickness Susceptibility Questionnaire (MSSQ) was completed. In an upright head position, without stimulation, the perceived head position was 1.1 degrees in controls and -0.69 degrees in vestibular migraine participants with no significant difference between groups. During galvanic vestibular stimulation, participants with vestibular migraine had an increased perception of head tilt compared with controls (RA/LC: controls -4.7 degrees and vestibular migraine -9.29, p = 0.002; and LA/RC: controls 6.5 degrees and vestibular migraine 11.12 degrees, p = 0.017), although the size of head movement was similar between groups. The average perception of head tilt correlated to the MSSQ score, but not to the degree of visual dependency in a static or moving background. A heightened sensitivity of the vestibular system to vestibular stimulation in vestibular migraine is consistent with reports of self-motion sensitivity in vestibular migraine.