Level diagnosis of cervical myelopathy using evoked spinal cord potentials

The ESCPs (evoked spinal cord potentials) resulting from both median nerve and spinal cord stimulation were recorded from the interlaminar yellow ligaments posteriorly or intervertebral discs anteriorly on patients with cervical myelopathy in order to determine the most significant lesion in the spinal cord electrophysiologically. The normal median-nerve-evoked spinal cord potential (MN-ESCP) consisted of P1N1 and N2(P2) deflections, while normal spinal cord-ascending evoked spinal cord potential (SC-AESCP) consisted of N1 and N2 deflections. The abnormal ESCPs obtained from 65 patients were classified into three grades. The spinal level recording the highest grade of ESCP, which was mostly positive wave, generally corresponded to the level that was clearly diagnosed as the main lesion by neurologic and radiologic examinations, such as a case of single level disc hernia. With these techniques, the level diagnostic rates of primary lesions were 94.7% in posterior recordings and 74.1% in anterior recordings.