Balance control impairment induced after OKS in patients with vestibular migraine: an intercritical marker.

The aim of the study was to assess the effects of optokinetic stimulation (OKS) on vestibular postural control in migraine patients with recurrent vertigo. 15 patients with vestibular migraine (VM) were enrolled in a posturographic study in eyes open (OE) and eyes closed (CE) condition. The tests were performed between attacks of headache and vertigo at three different time: before, during, and 60 min after OKS. Data of patients with VM were compared with those obtained from two control groups matched for sex and age (15 for each group): (a) normal subjects not suffering from migraine without history of recurrent vertigo (N group); (b) subjects suffering from migraine with no history of recurrent vertigo (M group). Mean sway path velocity and sway area were analyzed. OKS increased the instability in all groups during the stimulus, and both the velocity and area values were higher in M and VM group. However, there was not significant difference between these two groups when stability was examined in OE condition before, during and after OKS stimulation. Conversely, in CE condition a significant greater instability was induced after OKS stimulation only in VM. In particular, post-stimulus values were significantly higher than the pre-stimulus one only in this group, while no significant difference was observed in other groups. A spatial analysis of the sway area evidenced that the instability induced by the OKS in VM group occurred along the direction of OKS. We suggest that this enhanced instability observed after OKS during the intercritical period may be considered an useful marker to support the diagnostic definition of VM in the absence of other vestibular signs.