Spinal evoked potentials from the cervical spine.

Spinal cord evoked potentials were recorded from spinous processes of the lumbar, thoracic, and cervical levels of the spinal column of normal cats in response to direct stimulation of the sciatic nerve and subcutaneous stimulation of the posterior tibial nerve. The typical primary response was altered by changes in location, magnitude, and frequency of the stimulation. Further changes in the primary response could be associated with spinal level of observation. Reduction in amplitude and decrease in signal complexity with increasing frequency of stimulus indicated the loss of the slower components of the primary response of average evoked potentials. Sharp reduction of signal amplitude and increase in latency was evident as the recording moved from L1 to C3 and C2.