[An experimental and clinical study of peripheral nerve potentials evoked by stimulating the spinal cord]

The purpose of this study was to evaluate a possible use of TNP (tibial nerve potentials evoked by stimulating the upper thoracic spinal cord) as waveforms for spinal cord monitoring. The results of an experimental study in cats indicate that TNP mainly conducts antidromically in the dorsal column of the spinal cord with a velocity of approximately 70 m/sec. TNP was not a motor-evoked potential, but it involved some potential conducted from the ventral root, which was very small in amplitude. In men, TNP consisted of several negative deflections of 20 msec in onset latency and 1 microV in amplitude. The peak latency and amplitude of TNP were used as parameters for monitoring. Using this method 40 cases with spinal disorders were monitored. During surgery, the peak amplitude of TNP fluctuated within a range of 20% of the control wave in 24 cases, increased in three cases, and decreased in six cases. There was no false negative monitoring. TNP could not be recorded in four cases, in which SC-DESCP was used for monitoring instead of TNP. TNP disappeared during operation in three cases and in one of the cases, the postoperative neurological status had deteriorated. The disappearance of TNP was considered to be a positive sign of postoperative neurological complications. This study has concluded that TNP can be used for spinal cord monitoring, especially in patients with thoracolumbar disorders.