Vestibular dysfunction in migraine: effects of associated vertigo and motion sickness

The mechanisms of vestibular migraine and motion sickness remain unknown. The aims of this study were to determine interictal vestibular dysfunction in migraineurs according to associated dizziness/vertigo and motion sickness, and to find out whether impaired uvulonodular inhibition over the vestibular system underlies the vestibular symptoms and signs by measuring tilt suppression of the vestibulo-ocular reflex (VOR). One hundred and thirty-one patients with migraine [65 with vestibular migraine (MV), 41 with migrainous dizziness (MD), and 25 with migraine only (MO)] and 50 normal controls underwent evaluation of vestibular function. Motion sickness was assessed using the motion sickness susceptibility questionnaire (MSSQ) and subjective scale. Compared with normal controls and MO group, patients with MV/MD showed increased VOR time constant (TC) and greater suppression of the post-rotatory nystagmus with forward head tilt. The mean MSSQ score and subjective scale were highest in MV group, followed by MD, MO, and controls (p = 0.002, p < 0.001). Multiple linear regression model analyses revealed that motion sickness is an independent factor of TC prolongation (p = 0.024). Twenty-eight (21.4%) patients with migraine also showed perverted head shaking nystagmus and 12 (9.2%) had positional nystagmus. In view of the increased tilt suppression of the VOR, we speculate that dysfunction of the nodulus/uvula may not account for the prolonged TCs in MD/MV. Instead, innate hypersensitivity of the vestibular system may be an underlying mechanism of motion sickness and increased TC in MD/MV. The increased tilt suppression may be an adaptive cerebellar mechanism to suppress the hyperactive vestibular system in migraineurs.