• Muneharu Ando, Tetsuya Tamaki, Kazuhiro Maio, Hiroki Iwahashi, Hiroshi Iwasaki, Hiroshi Yamada, Toshikazu Tani, Takanori Saito, and Jun Kimura.
• Department of Orthopedic Surgery, Kansai Medical University, 2-3-1Shin machi, Hirakata City, Osaka, 573-1191, Japan. mando@gaia.eonet.ne.jp.
• J Clin Monit Comput. 2022 Aug 1; 36 (4): 1053-1067.

AbstractTo study if spinal motor evoked potentials (SpMEPs), muscle responses after electrical stimulation of the spinal cord, can monitor the corticospinal tract. Study 1 comprised 10 consecutive cervical or thoracic myelopathic patients. We recorded three types of muscle responses intraoperatively: (1) transcranial motor evoked potentials (TcMEPs), (2) SpMEPs and (3) SpMEPs + TcMEPs from the abductor hallucis (AH) using train stimulation. Study 2 dealt with 5 patients, who underwent paired train stimulation to the spinal cord with intertrain interval of 50-60 ms for recording AH SpMEPs. We will also describe two illustrative cases to demonstrate the clinical value of AH SpMEPs for monitoring the motor pathway. In Study 1, SpMEPs and SpMEPs + TcMEPs recorded from AH measured nearly the same, suggesting the collision of the cranially evoked volleys with the antidromic signals induced by spinal cord stimulation via the corticospinal tracts. In Study 2, the first and second train stimuli elicited almost identical SpMEPs, indicating a quick return of transmission after 50-60 ms considered characteristic of the corticospinal tract rather than the dorsal column, which would have recovered much more slowly. Of the two patients presented, one had no post-operative neurological deteriorations as anticipated by stable SpMEPs, despite otherwise insufficient IONM, and the other developed post-operative motor deficits as predicted by simultaneous reduction of TcMEPs and SpMEPs in the face of normal SEPs. Electrical stimulation of the spinal cord primarily activates the corticospinal tract to mediate SpMEPs.© 2021. The Author(s), under exclusive licence to Springer Nature B.V.

14 keywords...

hide…