Spinal Cord Potentials Evoked by Ascending Volleys

Abstract

Segmentally evoked SCPs are recordable over several segments in cats (Bernhard, 1953; Lupa and Niechaj, 1977), monkeys (Barron and Matthews, 1938), and humans (Shimoji et al., 1971, 1972). Recording electrodes situated more rostrally, however, do not detect the slow negative (N1) and positive (P2) waves, but only small spike-like potentials (Fig. 2.1). These spike-like potentials seem to reflect compound action potentials in ascending tracts within the cord and are more consistently evoked by epidural stimulation of the cauda equina or lumbosacral enlargement than by peripheral nerve stimulation. Figure 2.1 shows specimen records of SCPs simultaneously led from the cervical and lumbosacral enlargements in response to stimuli applied from the posterior epidural space (PES) to the cauda equina at the L3–4 vertebral level (Maruyama et al., 1982).