Interictal cortical hyperexcitability in migraine patients demonstrated with transcranial magnetic stimulation

Cortical excitability to magnetic stimulation was investigated interictally in 10 patients with migraine with aura, 10 with migraine without aura and in 10 healthy volunteers. Thresholds, latencies and amplitudes of the magnetic-evoked potentials (MEPs) were measured from threshold to 100% stimulus intensity in 10% steps. Compound motor action potentials (CMAPs) evoked with supramaximal electrical stimulation of the ulnar nerve were used to calculate MEP/CMAP amplitude ratios. Thresholds and latencies of MEPs did not differ between patients and controls. MEP/CMAP amplitude ratios were significantly increased at all intensities in patients with migraine with aura (RM-ANOVA, p < 0.01) and without aura (p < 0.05) compared with controls. In migraine patients, MEP amplitudes and MEP/CMAP amplitude ratios were positively related to the frequency of migraine attacks (Spearman's r = 0.47, p < 0.01 and r = 0.56, p < 0.002, respectively). MEP parameters were not related to the side of the headache nor the aura, in either type of migraine, implying that both hemispheres are equally involved in migraine. Migraine with aura and, to a lesser extent, migraine without aura, are associated with increased interictal cortical excitability.