Abnormal habituation of 'nociceptive' blink reflex in migraine evidence for increased excitability of trigeminal nociception

We studied the habituation of the 'nociceptive' blink reflex (nBR) in 15 healthy subjects and 17 migraine patients interictally as well as during unilateral migraine headache within six hours of onset and after treatment. In healthy volunteers the mean regression coefficient (MRC) was -3.9 following right sided and -4.9 left sided stimulation. This equals an amplitude loss of 19.5% (5 x -3.9) and 24.5% (5 x -4.9), respectively, across five consecutive sweeps. An augmentation of nBR responses was found in migraine patients interictally: MRC = 3.3 following stimulation of the headache side (HA) and MRC = 4.0 of the non-headache side (non-HA). The differences were statistically significant ( ANOVA : d.f. = 1, F = 25.8, P <0.001). During the migraine attack MRCs were negative both before (-5.0, HA and -4.0, non-HA) and after treatment (-2.6, HA and -1.9 non-HA) and significantly differed from those outside the migraine attack ( ANOVA : d.f. = 2, F = 12.4, P < 0.001). The demonstrated lack of habituation of the nBR responses indicates an abnormal trigeminal nociceptive processing in migraine patients outside the migraine attack.