Spinal cord stimulation and rehabilitation in an individual with chronic complete L1 paraplegia due to a conus medullaris injury: motor and functional outcomes at 18 months

Abstract

Introduction: Epidural electrical stimulation of the conus medullaris has helped facilitate native motor recovery in individuals with complete cervicothoracic spinal cord injuries (SCI). A theorized mechanism of clinical improvement includes supporting central pattern generators intrinsic to the conus medullaris. Because spinal cord stimulators (SCS) are approved for the treatment of neuropathic pain, we were able to test this experimental therapy in a subject with complete L1 paraplegia and neuropathic genital pain due to a traumatic conus injury.

Case presentation: An otherwise healthy 48-year-old male with chronic complete L1 paraplegia with no zones of partial preservation (ZPP) and intractable neuropathic genital pain presented to our group seeking nonmedical pain relief and any possible help with functional restoration. After extensive evaluation, discussion, and consent, we proceeded with SCS implantation at the conus and an intensive outpatient physical therapy regimen consistent with the recent SCI rehabilitation literature.

Discussion: Intraoperatively, no electromyography (EMG) could be elicited with epidural conus stimulation. At 18 months after implantation, his motor ZPPs had advanced from L1 to L5 on the left and from L1 to L3 on the right. Qualitative increases in lower extremity resting state EMG amplitudes were noted, although there was no consistent evidence of voluntary EMG or rhythmic locomotive leg movements. Three validated functional and quality of life (QoL) surveys demonstrated substantial improvements. The modest motor response compared to the literature suggests likely critical differences in the anatomy of such a low injury. However, the change in ZPPs and QoL suggest potential for neuroplasticity even in this patient population.

Fig. 1. Presenting MRI and X-ray.

Clinical T2-weighted MRI (left) and lateral spine x-ray (right) showing the extent of the patient’s injury and reconstruction before implantation of the epidural SCS.

Fig. 2. Post-SCS Implantation CT Scan.

Postoperative CT scan showing the placement of the paddle lead in the dorsal epidural space spanning T12-L1.

Fig. 3. Paddle Lead Configuration and Settings.

Paddle lead configuration (left) and initial settings (right).

Fig. 4. ISNCSCI Assessments.

a Preoperative and b 18-month post operative ISNCSCI assessments. The green circles denote areas of change.

Fig. 5. Resting Lower Extremity EMGs.

Sample of resting lower extremity EMGs recorded preoperatively (left) and 14 months post operatively (right). A qualitative increase spontaneous activity can be noted in all lower extremity muscles on the 14-month post operative assessment compared to preoperatively. However, no evidence of voluntary EMG modulation could be elicited.