Removal of schwannoma from the psoas muscle with intraoperative neurophysiological monitoring: A case report.

Abstract

The incidence of a schwannoma within the psoas muscle is rare, and only a few cases have been reported. The surgical approach to removing schwannomas present in the psoas muscle is challenging because of its anatomical proximity to the lumbar plexus. A 31-year-old man experienced right lower back pain and anterolateral thigh numbness for 2 months. Magnetic resonance imaging of the patient's lumbar spine revealed a mass lesion, which was radiologically diagnosed as a well-demarcated schwannoma. The patient underwent surgery for excision of the schwannoma in the right psoas muscle at the second to fourth lumbar vertebrae levels. During surgery, intraoperative neurophysiological monitoring modalities, free-running and triggered electromyography and evoked potentials, from the target muscles were recorded. There was no neurotonic discharge corresponding to neuronal injury. Compound motor nerve action potential was detected in the triggered electromyography of muscles around the medial margin of the tumor. However, direct integration of the motor nerve was not observed in the intra-tumor region. We report that schwannoma removal in the psoas muscle, which is adjacent to the lumbar plexus, can be safely performed using intraoperative neurophysiological monitoring.