MONITORING OF MOTOR TRACTS WITH SPINAL-CORD STIMULATION

Study Design. Sensory- and motor-evoked potentials were recorded after high thoracic (T2) epidural electrical stimulation of the spinal cord . Under general anesthesia, 22 cats underwent single or repetitive spi nal cord stimulation. Objectives. Sensory-evoked potentials were recor ded after antidromic activation of the posterior column sensory fibers at lower electrical intensities (<5 V). Motor tract activation was ac complished by recording the ventral root and muscle action potential u sing single pulse stimulation (>50 V). Methods. Sensory-evoked potenti als were recorded from the lumbar spinal cord (n = 20), dorsal root (n = 80), and peroneal nerve (n = 40). Motor-evoked potentials were reco rded from the ventral root (n = 40) and the hindlimb musculature (n = 10). Results. The lumbar spinal-evoked response resisted lesioning and showed a minimal change after a spinal cord hemisection. Dorsal rhizo tomy abolished the ipsilateral peroneal nerve action potential, indica ting antidromic activation of afferent fibers. Motor responses did not change after the dorsal rhizotomy, suggesting involvement of nonsenso ry pathways. Conclusions. These findings indicate that spinal cord sti mulation activates sensory and motor tracts that can be recorded at va rious sites along the central or the peripheral nervous system.