Somatosensory gating is altered and associated with migraine chronification: A magnetoencephalographic study

Background: Brain excitability is changed in migraine but not fully characterized yet. This study explored if somatosensory gating is altered in migraine and linked to migraine chronification. Methods: Paired electrical stimuli were delivered to the left index fingers of 21 patients with migraine without aura (MO), 22 patients with chronic migraine (CM), and 36 controls. The first and second responses to the paired stimuli were obtained from the contralateral primary (cSI), contralateral secondary (cSII) and ipsilateral secondary (iSII) somatosensory cortices to compute the gating ratios (second vs. first response strengths). Results: The first and second cSI responses and gating ratios differed in all groups (p < 0.05); the responses were typically smaller in the MO and CM groups. The cSI gating ratio increased as a continuum across controls (0.73 ± 0.04, p < 0.001), MO (0.83 ± 0.04) to CM (0.97 ± 0.06) and was higher in CM vs. controls (p < 0.001). When MO and CM were combined, cSI gating ratio was associated with headache frequency (r = 0.418, p = 0.005). Paired responses and gating ratios of cSII and iSII did not differ among the groups. Conclusions: Somatosensory gating is altered in migraine and associated with headache chronification. Further studies must clarify if this abnormal sensory modulation is a true gating deficit independent of low preexcitation level.