Experience of Diagnosis of Thoracic Myelopathy Using Spinal Cord Evoked Potentials

Conducted spinal cord evoked potentials (SEPs) were elicited preoperatively from the thoracic epidural space following spinal cord stimulation in 22 patients with thoracic myelopathy. The waveform changes in SEPs, namely, decrease of amplitude or positive-going potentials were observed and proved to be a successful method for determining the main lesions in all cases. In 20 patients with compressive myelopathy, waveform changes were recorded at the most compressed site in each case. A decrease in amplitude of more than 70% was demonstrated frequently in the moderately involved patients, whereas positive-going potentials were elicited predominantly in the patients with severe myelopathy. The waveform changes reflected to some extent the severity of the neurological symptoms; however, it was not possible to estimate the prognosis of the postoperative neurological symptoms by studying the preoperative SEP waveform. Conducted SEPs provide important information regarding determination of the surgical procedure and range of surgical decompression.