Nobuaki Tadokoro1, Toshikazu Tani2, Masahiko Ikeuchi2, Ryuichi Takemasa2, Kazunobu Kida2, Tatsunori Ikemoto3, Takahiro Ushida4, Shinichirou Taniguchi5, Jun Kimura6. 1. Department of Orthopaedic Surgery, Kochi Medical School, Japan. Electronic address: nobuaki.tadokoro@gmail.com. 2. Department of Orthopaedic Surgery, Kochi Medical School, Japan. 3. Department of Orthopaedic Surgery, Kuroshio Hospital, Japan. 4. Multidisciplinary Pain Center, Aichi Medical School, Japan. 5. Department of Orthopaedic Surgery, Kansai Medical University Takii Hospital, Japan. 6. Department of Neurology, University of Iowa, United States.
Abstract
OBJECTIVES: To characterize waveform changes of descending spinal cord evoked potentials (D-SCEPs) seen in cervical spondylotic myelopathy (CSM). METHODS: Intraoperative D-SCEP recording from serial intervertebral discs after transcranial electrical stimulation in 19 CSM patients with cord compression at a single level. RESULTS: Compared to the baseline (100%) obtained one level rostrally, the D-SCEP recorded at the compression site showed a significantly (p<0.001) decreased amplitude (48%) and area (48%) of negative peak and increased amplitude (171%) and area (279%) of initial-positive peak. The degree in reduction of negative peak remained the same irrespective of the cord level involved, whereas enhancement of the positive peak tended to diminish with a more caudal compression. CONCLUSIONS: In intraoperative electrophysiological studies of CSM with D-SCEP, an abrupt reduction of the negative peak accompanied by an enhancement of the initial-positive peak helps identify the site of conduction block. We speculate that progressive loss of the descending motor volleys at the synapses in the cervical enlargement may account for limited or absent enhancement of positive peak seen caudally. SIGNIFICANCE: The current finding helps us understand the pros and cons of various electrophysiologic techniques for intraoperative localization of maximal cord involvement in CSM.
OBJECTIVES: To characterize waveform changes of descending spinal cord evoked potentials (D-SCEPs) seen in cervical spondylotic myelopathy (CSM). METHODS: Intraoperative D-SCEP recording from serial intervertebral discs after transcranial electrical stimulation in 19 CSM patients with cord compression at a single level. RESULTS: Compared to the baseline (100%) obtained one level rostrally, the D-SCEP recorded at the compression site showed a significantly (p<0.001) decreased amplitude (48%) and area (48%) of negative peak and increased amplitude (171%) and area (279%) of initial-positive peak. The degree in reduction of negative peak remained the same irrespective of the cord level involved, whereas enhancement of the positive peak tended to diminish with a more caudal compression. CONCLUSIONS: In intraoperative electrophysiological studies of CSM with D-SCEP, an abrupt reduction of the negative peak accompanied by an enhancement of the initial-positive peak helps identify the site of conduction block. We speculate that progressive loss of the descending motor volleys at the synapses in the cervical enlargement may account for limited or absent enhancement of positive peak seen caudally. SIGNIFICANCE: The current finding helps us understand the pros and cons of various electrophysiologic techniques for intraoperative localization of maximal cord involvement in CSM.