Abstract
BackgroundMigraineurs seem to have cyclic variations in cortical excitability in several neurophysiological modalities. Laser-evoked potentials (LEP) are of particular interest in migraine because LEP specifically targets pain pathways, and studies have reported different LEP-changes both between and during headaches. Our primary aim was to explore potential cyclic variations in LEP amplitude and habituation in more detail with a blinded longitudinal study design.MethodsWe compared N1 and N2P2 amplitudes and habituation between two blocks of laser stimulations to the dorsal hand, obtained from 49 migraineurs with four sessions each. We used migraine diaries to categorize sessions as interictal (> one day from previous and to next attack), preictal (< one day before the attack), ictal or postictal (< one day after the attack). Also, we compared 29 interictal recordings from the first session to 30 controls.ResultsN1 and N2P2 amplitudes and habituation did not differ between preictal, interictal and postictal phase sessions, except for a post hoc contrast that showed deficient ictal habituation of N1. Habituation is present and similar in migraineurs in the interictal phase and controls.ConclusionsHand-evoked LEP amplitudes and habituation were mainly invariable between migraine phases, but this matter needs further study. Because hand-evoked LEP-habituation was similar in migraineurs and controls, the present findings contradict several previous LEP studies. Pain-evoked cerebral responses are normal and show normal habituation in migraine.
Highlights
Migraineurs seem to have cyclic variations in cortical excitability in several neurophysiological modalities
The results are not entirely coherent, but deficient N2P2-habituation has been observed in the interictal phase [17,18,19, 21, 22], a deficit that seems to persist during attacks [21]
N1-habituation was significant in the interictal phase as shown by the negative coefficient of block (Fig. 3 and Table 3)
Summary
Migraineurs seem to have cyclic variations in cortical excitability in several neurophysiological modalities. The apparently reduced LEP-habituation in migraineurs do not differ systematically between stimulation sites [17, 18, 20,21,22], and whether the N1 or N2P2potential are best suited to demonstrate an alteration is not clear [17, 20]. These results for LEP N2P2 should be independently confirmed [28]. N1-habituation should be studied further in migraine as only two studies have recorded this early LEP-component [17, 20]
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