Excitability of the motor cortex in patients with migraine changes with the time elapsed from the last attack

Abstract

BackgroundMotor-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.MethodsTwenty-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.ResultsThe 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).ConclusionOur 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.

Reduced Short‐Latency Afferent Inhibition Indicates Impaired Sensorimotor Integrity During Migraine Attacks

“…There are very inconsistent results about these parameters in current literature in migraine patients. Decreased or similar intracortical inhibition found in interictal migraineurs compared to controls. ICF is considered as a sum of the NMDA glutamatergic facilitation and GABA‐related inhibition .…”

“…4 Resting motor threshold (RMT), cortical silent period (CSP), short-interval intracortical inhibition (SICI), long-interval intracortical inhibition (LICI), and intracortical facilitation (ICF) are parameters that represent different intracortical motor inhibitory and facilitatory mechanisms. [5][6][7] Studies about RMT found no significant difference between interictal migraineurs and healthy controls, [8][9][10] but RMT seems to be related to the time elapsed between migraine attack and measurement. 9 CSP, SICI, and LICI are related to motor cortical GABAergic inhibition mechanisms.…”

“…[5][6][7] Studies about RMT found no significant difference between interictal migraineurs and healthy controls, [8][9][10] but RMT seems to be related to the time elapsed between migraine attack and measurement. 9 CSP, SICI, and LICI are related to motor cortical GABAergic inhibition mechanisms. 7 There are very inconsistent results about these parameters in current literature in migraine patients.…”

Gaba and Glutamate Changes in Pediatric Migraine

“…There is increasing evidence that adult migraine results from an imbalance of excitation/inhibition in the brain, which changes cyclically until a migraine occurs (known as the migraine cycle). 8,9 During the interictal period, excitability of the cortex increases proportionally with time to the next attack. During the migraine or shortly thereafter, the brain returns back to baseline activity and begins the cycle again.…”

“…During the migraine or shortly thereafter, the brain returns back to baseline activity and begins the cycle again. 8,9 Neurophysiological studies suggest this cortical hyperexcitability is a result of abnormal thalamic control. 10 Studies have revealed that, in migraine, there is altered communication in the thalamo-cortical networks11 which underlie important processes in multisensory integration; this altered communication is associated with clinical migraine symptoms.…”