The feasibility of intra-operative neurophysiologic monitoring using rectus abdominis muscles during thoracic tumor surgery: a case report

Abstract

Intraoperative neurophysiologic monitoring (IONM) has been widely used to prevent nerve damage during spinal tumor surgery. However, when the tumor is located in the thoracic vertebrae, it is impossible to monitor lower motor neurons such as nerve roots by conventional methods. To solve this problem, the rectus abdominis muscle, which is innervated by the thoracic nerve root, can be used. We report a case using the rectus abdominis motor evoked potentials (MEP) and free-running electromyography in a patient with schwannoma located at the T12 thoracic vertebrae. During surgery, a reduction in MEP was seen upon removal of the tumor, but not less than 50%. Neurotonic discharge was seen upon removal of the tumor, but was not sustained. After the operation, the patient did not report any neurological symptoms. This case supports that MEP and free-running electromyography of the rectus abdominis muscle can be feasible for monitoring in thoracic spine surgery.