Free-running and triggered electromyography during intraoperative neuromonitoring

Abstract

Intraoperative electromyography (EMG) is known to record compound muscle action potential (CMAP) in response to spontaneous or stimulated cranial nerve or spinal root activation. EMG can detect cranial nerve or spinal nerve root irritation (known as free-running EMG), and may involve electrical stimulation of neural elements or hardware to assess function (known as stimulated or triggered EMG). EMG has a low positive predictive value with high sensitivity, which is particularly useful in the early detection and prevention of pending nerve injury. EMG is one the most useful modalities of intraoperative neuromonitoring (IONM) for monitoring neural function along with sensory and motor evoked potentials during surgery associated with spinal manipulation and cranial nerve involvement.