Absent Baseline Intraoperative Neuromonitoring Signals Part I: Adolescent Idiopathic Scoliosis

One of the most important tools we have to enhance patient safety during spine surgery for adolescent idiopathic scoliosis (AIS) is the combined use of somatosensory (SSEP) and motor (MEP) evoked potentials. Both are recommended because it increases the sensitivity and reliability of signals in the AIS population and thereby increases patient safety. In the case of the absence or a decrease of MEP/SSEP signals, the surgical team must problem solve these changes in a controlled and systematic manner. The purpose of this review is to discuss the following conditions which may lead to these changes. These include technical issues, anesthetic protocol, patient positioning, patient temperature, and blood pressure. If troubleshooting is unsuccessful and satisfactory preoperative signals are unable to be obtained, a Stagnara wake-up test may result in improved signals as the sedation decreases. Continued absence of signals, however, may lead to termination of the procedure and necessitate further testing. For cases in which decreased or absent neuromonitoring signals are seen during any point in the procedure, the patient should be admitted to the surgical floor or PICU postoperatively. Key Concepts: • In the event of decreased or absent MEP/SSEP signals, the surgical team must consider pre-existing challenges such as technical issues, anesthetic protocol, and patient positioning prior to any next steps. • In cases where reduced or absent IONM signals still persist, a Stagnara wake-up test may yield optimal results. • If all interventions fail to revive IONM, surgery must be aborted, and in-depth testing must be conducted in order to determine potential causes prior to proceeding with surgery.