INTERICTAL CORTICAL EXCITABILITY IN MIGRAINE - A STUDY USING TRANSCRANIAL MAGNETIC STIMULATION OF MOTOR AND VISUAL CORTICES

We performed transcranial magnetic stimulations of the motor and visua l cortices in healthy controls (n = 27) and in patients suffering from migraine without (n = 33) or with (n = 25) aura between attacks. By u sing a 13-cm circular coil placed over the vertex and recordings of th e first dorsal interosseus muscle, we measured thresholds (at rest and during contraction), amplitudes of motor evoked potentials and cortic al silent periods. Paired stimulations with short (1-20 msec) intersti mulus intervals were performed to assess intracortical inhibition. The visual cortex was stimulated with the same coil placed over the occip ital scalp (7 cm above the inion) and the prevalence and threshold of phosphene production was determined. In patients with migraine with au ra, motor thresholds during isometric contraction were significantly h igher, whereas the prevalence of stimulation-induced phosphene product ion was lower compared with healthy controls. These changes were not c orrelated with attack frequency or disease duration. No differences we re found between subject groups in thresholds at rest, motor evoked po tential amplitudes, cortical silent periods, or response curves after paired stimuli. These results are in favor of cortical hypoexcitabilit y rather than hyperexcitability in patients with migraine with aura be tween attacks.