Volume 16 Supplement 1
O025. Excitability of the motor cortex in migraine changes with the distance from the last attack
© Coppola et al. 2015
Published: 28 September 2015
Single-pulse transcranial magnetic stimulation studies of motor cortex have the advantage of relying on an objective measure, the motor evoked potential (MEP) recorded in peripheral muscles, to non-invasively explore the cortical excitability. Previously, thresholds for MEP were found to be normal, increased or even reduced in migraine. In the present study, we investigated whether the level of cortical excitability changes with the distance from the last migraine attack could explain these inconsistent results.
Twenty-six patients with untreated migraine without aura (MO) underwent MEP study between attacks and were compared to a group of 24 healthy volunteers (HV). The TMS figure-of-eight coil was positioned over the left motor area. We first identified the resting motor threshold (RMT) and then amplitude of MEP was evaluated by delivering and averaging 10 single pulses of TMS using a stimulus intensity of 120% RMT at a rate of 0.1 Hz.
Mean RMTs (54.2 in MO vs. 55.8 in HV) and MEP amplitudes (3057 V in MO vs. 3675 V in HV) were not significantly different between MO and HV. In MO, the RMT negatively correlated with days elapsed since the last migraine attack (r = -0.426, p = 0.03).
From the present data emerges that the threshold for evoking MEP is influenced by the proximity of an attack since it is minimal at a long time interval after an attack, while it is greater and within the range of normative values approaching an attack. The dynamic RMT variations found here resemble those we had previously reported for visual and somatosensory evoked potentials, and may represent time-dependent plastic changes in brain excitability in relation with the migraine cycle.
Written informed consent to publish was obtained from the patient(s).
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.