Vector analysis of visual evoked potentials in migraineurs with visual aura

Objective: To assess the capability of vector analysis of visual evoked potentials (VEPs) for revealing alterations in posterior visual pathways in migraineurs with visual aura. Methods: VEPs to pattern reversal (PR) and LED goggle stimulation were obtained in 23 patients suffering from migraine with visual aura, in an orthogonal Fpz–Oz and T3–T4 montage and displayed as a two-channel Lissajousʹ trajectory. VEP latency and amplitude at Fpz–Oz, bc segment amplitude (V) and bc vector orientation angle (θ) were compared with a previously collected normative database for individual assessment, and group comparisons with the previously collected normal sample were made. Electrophysiological measures were also correlated with time from onset of disease and from the last crisis, and with the side of symptoms. Results: No individual alterations in VEP latency or amplitude were observed. However, 36.4% of patients showed alterations in vector orientation to PR and 78% to LED goggles. Group differences with respect to normal subjects were found not only in vector orientation but also in midline VEP and V, only for PR stimulation. A significant relationship was found between the laterality of vector deviation and the laterality of symptoms. Conclusions: Vector analysis of VEP revealed alterations possibly corresponding to asymmetrical visual cortex activation in migraineurs with visual aura, mainly to diffuse light stimulation. Significance: An electrophysiological parameter of individual value for revealing asymmetric activation of visual cortex in migraineurs is proposed.