Free running and triggered electromyography for surgical planning during spinal cord tumor removal: a case report

Intraoperative neurophysiological monitoring (IONM) for spinal cord tumor surgery is vital to prevent postoperative neurological complications. While evoked potentials are fundamental, electromyography (EMG) is often underestimated. We present a case where EMG was crucial. A 79-year-old man with a spinal cord tumor at T12-L1 underwent surgery with IONM, including motor evoked potentials (MEPs), somatosensory evoked potentials (SEPs), free-running EMG (fEMG), and triggered EMG (tEMG). MEPs and SEPs remained stable during surgery, but fEMG detected B-trains in the right tibialis anterior and abductor hallucis muscles, promptly alerting the surgeon. Additionally, tEMG identified compound muscle action potentials in the right abductor hallucis during tumor removal at the conus medullaris. As a result, en-bloc resection was converted to subtotal removal. The patient experienced transient numbness in the right L5 and S1 dermatomes but no further weakness. This case emphasizes the importance of EMG in ensuring safety during spinal tumor surgeries.