Chapter 21 - Spinal cord monitoring

Abstract

Spinal cord surgery carries the risk of spinal cord or nerve root injury. Neurophysiologic monitoring decreases risk of injury by continuous assessment of spinal cord and nerve root function throughout surgery. Techniques include somatosensory evoked potentials (SEPs), transcranial electrical motor evoked potentials (MEPs), and electromyography (EMG). Baseline neurophysiologic data are obtained prior to incision. Real-time signal changes are identified in time to correct compromised neural function. Such monitoring improves postoperative neurologic functional outcomes. Challenges in neurophysiologic intraoperative monitoring (NIOM) include effects of anesthetics, neuromuscular blockade, hypotension, hypothermia, and preexisting neurological conditions, e.g., neuropathy or myelopathy. Technical factors causing poor quality data must be overcome in the electrically noisy operating room environment. Experienced monitoring teams understand tactics to obtain quality recordings and consider confounding variables before raising alarms when change occurs. Once an alert is raised, surgeons and anesthesiologists respond with a variety of actions, such as raising blood pressure or adjusting retractors. In experienced hands, NIOM significantly reduces postoperative neurological deficits, e.g., 60% reduction in risk of paraplegia and paraparesis. A technologist in the operating room sets up the NIOM procedure. An experienced clinical neurophysiologist supervises the case, either in the operating room or remotely on-line continuously in real time.