Postural changes and motor evoked potentials following percutaneous spinal cord epidural stimulation in spinal cord injury

INTRODUCTION: Percutaneous spinal cord epidural stimulation (pSCES) is an effective modality for managing pain. However, the use of pSCES in restoration of motor control after SCI is still under research exploration. Today, the effects of postural changes on pSCES-motor control are still controversial. CASE PRESENTATION: Two participants with complete SCI underwent implantation of pSCES. The motor recruitment curves of motor units of two different agonist-antagonist muscle groups were captured in a supine position and in a standing position using a standing frame. The amplitudes of the motor evoked response were presented in absolute or relative to the maximum response. Both narrow and wide field pSCES configurations elicited intensity-dependent EMG responses across lower-limb muscles, with substantially greater amplitudes in supine compared to standing. Transitioning to standing produced marked bilateral attenuation of raw responses across muscles and configurations, although relative recruitment patterns were partially preserved following EMG normalization. Increasing pulse duration broadened relative muscle recruitment and enhanced distal muscle activation, but posture remained the dominant determinant of overall response magnitude. DISCUSSION: Standing posture was associated with substantial attenuation of pSCES-evoked responses across muscles and stimulation parameters, indicating posture-dependent modulation of evoked muscle activation following pSCES implantation in persons with SCI.