Vestibular function in migraine-related dizziness: a pilot study.

Migraine-related dizziness (MRD) refers to a disorder in which vestibular symptoms are an integral part of migraine symptomatology. The purpose of this study was to better define the pathophysiology of MRD, which is incompletely understood and to generate hypotheses regarding MRD by assessing the semicircular canal-ocular reflex, the otolith-ocular reflex, visual-vestibular interaction, vestibulo-spinal function, and visually induced postural sway. Subjects included five subjects with MRD, five subjects with migraine without dizziness, and five headache-free controls. Subjects with migraine were tested interictally. Results indicated that the mean gain of the semicircular canal-ocular reflex during both sinusoidal and constant velocity rotation was reduced in subjects with MRD. No changes were noted in the dynamics of the semicircular canal-ocular reflex. The otolith-ocular reflex, assessed with constant velocity OVAR, indicated that subjects with MRD showed a larger modulation component. No group differences were found in the bias component during constant velocity OVAR, nor in semicircular canal-otolith interaction or visual-vestibular interaction. Computerized dynamic posturography indicated that subjects with MRD demonstrated a surface-dependent pattern. Postural sway during optic flow indicated that subjects with MRD swayed more than the other subjects. We hypothesize that competing processes of serotonergic excitation and inhibition alter central vestibular pathways differently for semicircular canal vs. otolithic responses and for vestibulo-ocular vs. vestibulo-spinal pathways.