Oscillating field stimulation for complete spinal cord injury in humans: a phase 1 trial

Abstract

Object: An electrical field cathode (negative pole) has trophic and tropic effects on injured spinal cord axons in in vitro and in vivo models of sea lamprey, rodent, and canine spinal cord injury (SCI) and it improves functional outcome. A human oscillating field stimulator (OFS) was built, a Food and Drug Administration (FDA) exemption number was obtained, and institutional review board approval was given for a Phase 1 trial to study 10 humans with complete motor and sensory SCI.

Methods: Entry criteria were complete SCI between C-5 and T-10 in patients 18 to 65 years of age and no transection demonstrated on magnetic resonance imaging. All participants received the National Acute Spinal Cord Injury Study (NASCIS) III methylprednisilone protocol. Cord compression and/or vertebral instability was treated before study entry. After treatment complete SCI (according to the American Spinal Injury Association [ASIA] score) remained in all patients with no somatosensory evoked potentials (SSEPs) below the injury level after surgery or for 48 hours. All patients underwent implantation of the OFS within 18 days. Patients underwent evaluation every 2 weeks postimplantation; the OFS was explanted at 15 weeks. Independent neurological status was assessed based on the ASIA score, visual analog scale (VAS) pain score, and SSEPs at 6 weeks, 6 months, and 1 year. Statistical analyses were performed using the two-tailed Wilcoxon test and analysis of variance (ANOVA). There were no complications at insertion of the OFS; there was one case of wound infection after explantation (5% infection rate). One patient was lost to follow up after 6 months. In all 10 patients the mean VAS pain score was 8 at implantation, 2 at 6 months, and in the nine attending follow up for 1 year it remained 2. At 1 year, the mean improvement in light touch was 25.5 points (ANOVA p < 0.001, Wilcoxon test p = 0.02), the mean improvement in pinprick sensation was 20.4 points (ANOVA p < 0.001, Wilcoxon test p = 0.02), and the mean improvement in motor status was 6.3 points (ANOVA p < 0.01, Wilcoxon test p = 0.02). Of five cases involving cervical cord injuries, bilateral upper-extremity SSEPs were normal in one, unilateral upper-extremity SSEPs were recovered in four, bilateral upper-extremity SSEPs were recovered in one, and abnormal lower-extremity SSEPs resolved in one case. In one of the five cases involving thoracic injuries an abnormal lower-extremity SSEP resolved.

Conclusions: The use of OFS treatment in patients with SCI is safe, reliable, and easy. Compared with the outcomes obtained in compliant NASCIS III plegic patients, the results of the present study indicate efficacy, and the FDA has given permission for enrollment of 10 additional patients.