Transcutaneous spinal stimulation (TSS) is emerging as a valuable tool for electrophysiological and clinical assessments.
The objectives of this study were to investigate: (1) TSS above and below a spinal cord injury (SCI) lesion results in different recruitment pattern of upper limb (UL) motor pools compared to neurologically intact subjects (NIS), and (2) the relationship between recruitment pattern of UL motor pools and neurological and functional status in individuals with SCI. Methods: Eleven NIS and six participants with cervical SCI were recruited in this study. We compared spinally evoked motor potentials in UL muscles during TSS delivered to the cervical spinal cord between the spinous process of C3-C4 and C7-T1 vertebrae.
As expected, TSS delivered over the cervical spinal cord in NIS can preferentially activate proximal and distal muscles along the rostrocaudal axis, as well as ipsilateral UL muscles along the mediolateral axis. However, in participants with SCI, the responses registered in UL muscles innervated by motor pools above and below the lesion demonstrated different recruitment compared to NIS, and were dependent on the level, extent, and side of SCI.
The spatial map obtained from assessing evoked potentials above and below the lesion contributes to the comprehensive understanding of the viability and function of specific UL motor pools, and can be utilized to monitor changes in recruitment patterns of the UL motor pools during neurorehabilitation interventions after SCI.
