Cervical epidural spinal cord stimulation is associated with enhanced voluntary upper-limb muscle activation in chronic post-stroke hemiparesis: a pilot feasibility study

Upper-limb hemiparesis is a prevalent and often refractory sequela of stroke, and conventional rehabilitation approaches often yield limited long-term gains in the chronic phase. Cervical epidural electrical stimulation (EES) has emerged as a promising precision neurorehabilitation strategy to amplify residual corticospinal drive through contact-specific modulation of spinal interneuron excitability. However, the relationship between individual cervical motor recruitment patterns and functional recovery has not been systematically characterized in stroke survivors. Therefore, the present prospective pilot study investigated contact-specific motor mapping and the acute effects of cervical EES on voluntary upper-limb muscle activation in four participants with chronic post-stroke hemiparesis. Four adults with chronic post-stroke hemiparesis (time since stroke 6–28 months; baseline Fugl-Meyer Assessment for Upper Extremity [FMA-UE] scores 6–35) underwent bilateral percutaneous cervical epidural lead implantation spanning C3–T1. Intraoperative contact-specific motor mapping was performed through bipolar stimulation at 2 Hz, yielding individualized cervical recruitment maps that informed subsequent parameter selection. Task-related surface electromyography (EMG) was then recorded under EES-On and EES-Off conditions across six standardized upper-limb movements; EES-On/EES-Off amplitude ratios served as indices of acute stimulation effects. Clinical assessments, including the FMA-UE, Action Research Arm Test (ARAT), and Modified Ashworth Scale (MAS), were administered at baseline and 12–28 days after implantation, with EES active. Intraoperative mapping showed a level-dependent proximal-to-distal pattern of muscle recruitment consistent with cervical somatotopic organization. EES-On was associated with higher voluntary EMG amplitude in most muscles and tasks, with EES-On/EES-Off ratios of up to 11.4 in the wrist flexor during grasping. All four participants had higher FMA-UE scores at the post-implantation assessment (range +4 to +8 points), with changes in three participants falling within or above the published minimal clinically important difference range, and ARAT scores increased in all four participants (+1 to +6 points). Elbow flexor tone increased in two participants, and no serious adverse events occurred. Collectively, these preliminary findings suggest that contact-specific cervical EES, informed by individualized motor mapping, may represent a feasible adjunct intervention for upper-limb rehabilitation following chronic stroke, and provide a neurophysiological rationale for future controlled trials. Clinical trial registration ClinicalTrials.gov , NCT05981989.