title: Excitability of the motor cortex in patients with migraine changes with the time elapsed from the last attack.
abstract: BACKGROUND
  Motor-evoked potentials (MEPs) produced by single-pulse transcranial magnetic stimulation (TMS) of the motor cortex can be an objective measure of cortical excitability. Previously, MEP thresholds were found to be normal, increased, or even reduced in patients with migraine. In the present study, we determined whether the level of cortical excitability changes with the time interval from the last migraine attack, thereby accounting for the inconsistencies in previous reports.
  
  
  METHODS
  Twenty-six patients with untreated migraine without aura (MO) underwent a MEP study between attacks. Their data were then compared to the MEP data collected from a group of 24 healthy volunteers (HVs). During the experiment, the TMS figure-of-eight coil was positioned over the left motor area. After identifying the resting motor threshold (RMT), we delivered 10 single TMS pulses (rate: 0.1 Hz, intensity: 120% of the RMT) and averaged the resulting MEP amplitudes.
  
  
  RESULTS
  The mean RMTs and MEP amplitudes were not significantly different between the MO and HV groups. In patients with MO, the RMTs were negatively correlated with the number of days elapsed since the last migraine attack (rho = -0.404, p = 0.04).
  
  
  CONCLUSIONS
  Our results suggest that the threshold for evoking MEPs is influenced by the proximity of an attack; specifically, the threshold is lower when a long time interval has passed after an attack, and is higher (within the range of normative values) when measured close to an attack. These dynamic RMT variations resemble those we reported previously for visual and somatosensory evoked potentials and may represent time-dependent plastic changes in brain excitability in relation to the migraine cycle.
authors.affiliation: Department of Medico-Surgical Sciences and Biotechnologies, 'Sapienza' University of Rome Polo Pontino, Corso della Repubblica 79, 04100, Latina, Italy. francesca.cortese05@libero.it.
authors.forename: Francesca
authors.initials: F
authors.lastname: Cortese
authors.affiliation: G. B. Bietti Foundation IRCCS, Research Unit of Neurophysiology of Vision and Neuro-Ophthalmology, Rome, Italy.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Coppola
authors.affiliation: Department of Medico-Surgical Sciences and Biotechnologies, 'Sapienza' University of Rome Polo Pontino, Corso della Repubblica 79, 04100, Latina, Italy.
authors.forename: Davide
authors.initials: D
authors.lastname: Di Lenola
authors.affiliation: Department of Medico-Surgical Sciences and Biotechnologies, 'Sapienza' University of Rome Polo Pontino, Corso della Repubblica 79, 04100, Latina, Italy.
authors.forename: Mariano
authors.initials: M
authors.lastname: Serrao
authors.affiliation: Don Carlo Gnocchi, Onlus Foundation, Milan, Italy.
authors.forename: Cherubino
authors.initials: C
authors.lastname: Di Lorenzo
authors.affiliation: G. B. Bietti Foundation IRCCS, Research Unit of Neurophysiology of Vision and Neuro-Ophthalmology, Rome, Italy.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Parisi
authors.affiliation: Department of Medico-Surgical Sciences and Biotechnologies, 'Sapienza' University of Rome Polo Pontino, Corso della Repubblica 79, 04100, Latina, Italy.|INM Neuromed IRCCS, Pozzilli, (IS), Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Pierelli
mesh_terms: D000328:Adult; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008881:Migraine Disorders / Q000503:physiopathology*; D009044:Motor Cortex / Q000503:physiopathology*; D013997:Time Factors; D050781:Transcranial Magnetic Stimulation / Q000379:methods*
keywords: Ictal; Interictal; Migraine; Motor threshold; Transcranial magnetic stimulation