Spinal cord evoked potentials in thoracic myelopathy with multisegmental vertebral involvement.

Spinal cord evoked potentials were recorded preoperatively from the thoracic epidural space after spinal cord stimulation in 20 patients with thoracic myelopathy with multisegmental vertebral involvement. Waveform abnormalities in spinal cord evoked potentials, namely, positive-going wave or decrease in amplitude, were observed in all cases. Abnormalities, especially in the first negative component of spinal cord evoked potentials, were recorded at the most compressed site in each case. Decrease in amplitude of more than 50% was noted frequently in moderately involved cases, whereas positive-going wave was elicited predominantly in cases of severe myelopathy. Spinal cord evoked potentials should provide information for determining the range of decompression in multisegmental vertebral involvement.