Visual evoked potential latency, amplitude and habituation in migraine: A longitudinal study

Objective It has not been previously studied with a paired longitudinal design if visual excitability changes occur in the preattack period across the migraine cycle, or how excitability and habituation relate to migraine-attack severity, clinical photophobia and serotonin metabolism. Methods Monocular 62′ check reversals were applied in 33 adult migraine patients without aura (MwoA), 8 with aura (MA) and 31 controls. VEP was recorded in four blocks of 50 stimuli. P1 (P100) and N2 (N145) latency and N1P1 and P1N2 amplitude were measured. Serotonin was measured in plasma and platelets sampled before each session. Sessions were classified as preattack, attack, postattack or interictal. Results Migraine patients had significantly higher P1N2 amplitude before the attack compared to a paired interictal recording (n = 13, p = 0.03), but habituation difference was not found. MA patients had significantly higher P1N2 and N1P1 amplitude than controls and MwoA. P1 latency correlated positively with headache history duration. During attack, a positive correlation between P1N2 amplitude habituation and serotonin emerged in MA patients. Conclusions Increased VEP P1N2 amplitude was observed within a few days before the attack. Visual cortex excitability seems to be generally increased in MA as compared to MwoA patients and controls. Significance Increased excitability of the visual cortex seems to be detectable in the preattack state, supporting the concept of a cyclic CNS dysfunction in migraine.