Motor Evoked Potential

Excerpt

Intraoperative injuries or ischemia to the brain, spinal cord, or peripheral nerves can be devastating. Damage to motor pathways can cause lifelong weakness or paralysis, resulting in significant reductions in the quality of life and permanent disability. Several neuromonitoring modalities have been developed to allow monitoring of neurologic function during surgeries associated with the risk of neurologic damage, such as surgeries on the brain, spine, or aorta. Commonly used neuromonitoring techniques include electroencephalogram (EEG), spontaneous electromyogram (EMG), somatosensory evoked potentials (SSEPs), and motor evoked potentials (MEPs).

Modalities are often used in combination to provide information on multiple neurologic pathways during a procedure. Collectively, intraoperative neuromonitoring techniques have largely replaced the "wake-up test" during surgery, as information regarding neuronal integrity can be obtained while the patient remains anesthetized. Clinically significant changes in neuromonitoring signals are detected in real-time by a neurophysiologist and relayed to the surgeon and anesthesiologist. Ideally, early detection of injury allows time for surgical or anesthetic changes to be made in order to prevent permanent neuronal damage.

The focus of this review is motor evoked potentials. The indications, contraindications, anatomy, physiology, the impact of anesthetics, and potential complications associated with MEP monitoring will be reviewed.