Modulation of thermal somatosensory thresholds within local and remote spinal dermatomes following cervical repetitive magnetic stimulation

Abstract Background : Repetitive magnetic stimulation (rMS) modulates thermal somatosensory function at both low (0.2–1.0 Hz) and high (5.0–20.0 Hz) frequencies within the conditioned dermatome. However the effects of 1 Hz and 20 Hz cervical (C6-C7) rMS on thermosensory thresholds and contact heat evoked potentials (CHEPs) tested within local and remote spinal dermatomes are not known. Methods : Thirty healthy subjects participated in the study. Warm and cold detection threshold, heat and cold pain thresholds, and Cz/Fz CHEPs were evaluated within the C6, T10 and extrasegmental V3 control dermatome, before and after random assignment of subjects to sham, 1 or 20 Hz C6-C7 rMS. Results : Following both 1 and 20 Hz cervical rMS, warm detection threshold increased within the local C6 dermatome. Furthermore 1 Hz cervical rMS increased warm detection threshold within the remote T10 dermatome, but not within the V3-trigeminal control area. Cervical rMS failed to modulate cold detection threshold, heat and cold pain threshold or Cz/Fz CHEP amplitude from the dermatomal test sites. Conclusion : Both 1 and 20 Hz cervical rMS modulated warm detection threshold within the locally conditioned C6 dermatome. The concomitant increase in warm detection threshold within the T10 dermatome following 1 Hz rMS provides evidence for remote neuromodulation of thermosensory function via intraspinal control mechanisms.