Decreased habituation of the R2 component of the blink reflex in migraine patients.

Objective: Activation of the trigemino-vascular system as well as of brainstem trigeminal nuclei are thought to play an important role in migraine. The aim of this study was to investigate the habituation phenomenon of the blink reflex in 30 headache-free migraine patients and 30 control subjects.

Methods: An electromyographic device with a specific habituation test program was used to elicit and record blink reflex responses on both the right and left sides, and to randomly repeat the stimulations at different time intervals in order to induce habituation.

Results: Whereas the R1 and R2 latencies, amplitudes and areas in the basal assessment were similar in patients and control subjects, the blink reflex habituation responses were markedly reduced in migraine patients who had a migraine attack within 72 h after testing (group A). In these patients, the differences between the R2 areas, obtained when stimuli were delivered at subsequent time intervals ranging between 10-5, 5-4, 4-3 and 3-2 s, were statistically different (P<0.001) from those of the patients who had a migraine attack after a longer time interval (group B) and control subjects.

Conclusions: Our data suggest that the brainstem pathways involved in the blink reflex may be activated in the premonitory phase of migraine attacks, probably through mechanisms that involve dopaminergic function.