Visual evoked potentials and background EEG activity in migraine

To investigate whether quantification of the background EEG during a visual evoked potential (VEP) study is of value for the diagnosis of migraine we studied 8 unmedicated migraineurs between attacks, and 10 age-matched controls. Three paradigms were used: the first two concerned pattern-reversal VEPs with different analysis times (500 and 1500 ms), and in the third paradigm the pattern did not reverse. Power spectra were calculated for individual responses, and the delta, theta, alpha and beta areas of the averaged spectra were noted as indicators of background reactivity. Alpha and beta powers were consistently but not significantly higher in the migraine group. The difference was too small to be of value as a diagnostic test. Alpha power was (not significantly) lower in the presence of photic stimulation than in its absence. As this was the case in both groups photic stimulation does not explain the higher alpha powers in the migraine group. We conclude that EEG background activity during the VEP does not distinguish reliably between migraineurs and controls.