Cortical trapezius muscle mapping using neuronavigated transcranial magnetic stimulation – feasibility and explorative application to the trigemino-cervical complex among patients with migraine

Background The trigemino-cervical complex (TCC) is part of migraine pathophysiology, bridging central with peripheral mechanisms of pain. The upper parts of the trapezius muscles show innervation profiles that converge with the TCC, yet cortical motor representations in migraine remain unexplored. We aimed to show the feasibility of cortical trapezius muscle mappings in migraine research, investigate derived cortical motor representations of the upper trapezius muscles in migraine, and assess associations with headache and stress coping characteristics. Methods 15 patients with migraine (mean age 26.3 ± 3.0 years; mean headache frequency 7.4 ± 3.2 days/month) and 15 healthy controls (HCs) underwent one session of bihemispheric cortical motor mapping by neuronavigated transcranial magnetic stimulation (nTMS) on a headache-free day, conducted after a 3-month observation period with a headache calendar. Motor-evoked potential (MEP) amplitudes and latencies were assessed for the upper trapezius muscles at two sites (medial and lateral part), after exclusion of outliers. Moreover, the distribution of motor-positive points for the medial or lateral parts of the trapezius muscles were assessed (primary motor cortex/M1, primary somatosensory cortex/S1, premotor cortex/PreMA, supplementary motor cortex/SMA). Associations of mapping results with headache characteristics and those from a stress coping questionnaire (SVF) were analyzed considering a false discovery rate of 10%. Results Neither stimulation intensities, mean MEP amplitudes, nor mean MEP latencies showed statistically significant differences between participants with migraine versus HCs. However, significantly higher numbers of motor-positive stimulation points among applied stimuli were found in areas located anteriorly of M1 (PreMA) in participants with migraine (p=0.02). Headache duration (from the headache calendar) as well as negative stress coping strategies (from the SVF) were strongly significantly associated with MEP amplitudes of the trapezius muscles (range of correlation coefficient r: 0.62–0.71, p<0.05). Conclusions According to the results of our explorative analyses, the spatial extent of the motor system’s cortical representations of the upper trapezius muscles may be different between participants with migraine and HCs, with potential associations of MEP amplitudes with headache characteristics and negative stress coping strategies. Those findings may point to a clinically relevant role of motor mappings of the upper parts of the trapezius muscles in migraine.