The effect of direct-current field on recovery from experimental spinal cord injury

Recent work has indicated that direct-current (DC) fields may promote recovery after acute spinal cord injury. In the present experiments, the therapeutic value of an applied DC field was studied in 40 rats with clip compression injuries of the cord at C7-T1. The rats were randomly allocated to one of four groups including 10 rats each: two groups received a 17-gm cord injury and two groups a 53-gm injury. One group at each injury severity received implantation of a treatment (14 microA) DC stimulator and the other group a control (0 microA) stimulator. Clinical neurological function was assessed weekly by the inclined-plane technique. At 8 weeks after injury, motor and somatosensory evoked potentials (MEP's and SSEP's) were recorded, and the axonal tracer horseradish peroxidase (HRP) was introduced into the cord at T-6. The total number of HRP-labeled cells was counted in every sixth coronal section through the brain stem and motor cortex. All outcome parameters were assessed blindly. In the 17-gm group, there were no significant differences in any outcome measure between control and treated rats. In contrast, in the 53-gm group, the inclined-plane scores, the amplitude of the MEP's, and the number of labeled cells in the red nucleus, raphé nuclei, and vestibular nuclei were greater in treated than in control rats. These data strongly indicate that an applied DC field can produce functional neurological and anatomical improvement in rats with acute spinal cord injuries.