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. PI (P100) and N2 (N145) latency and NIPI and PIN2 amplitude were measured. Serotonin was measured in plasma and platelets sampled before each session. Sessions were classified as preattack, attack, post-attack or interictal. Results: Migraine patients had significantly higher PIN2 amplitude before the attack compared to a paired interictal recording (17 13, p = 0.03), but habituation difference was not found. MA patients had significantly higher PIN2 and NIPI amplitude than controls and MwoA. PI latency correlated positively with headache history duration. During attack, a positive correlation between PIN2 amplitude habituation and serotonin emerged in MA patients. Conclusions: Increased VEP PIN2 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. (c) 2008 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.