Update on neuromonitoring procedures applied during surgery of the spine - observational study.

Introduction: Motor evoked potentials (MEPs) are currently considered as a more useful method for neurophysiological intraoperative monitoring than somatosensory evoked potentials in cases of surgery applied to patients with adolescent idiopathic scoliosis. The non-invasive approach is preferred to modify MEP recordings, criticizing, in many cases, the fundamentalism for neurophysiological monitoring based only on needle recordings. The aim of the review is to provide our own experience and practical guidelines with reference to neuromonitoring innovations. Material and methods: Recordings of MEPs with surface electrodes instead of needle electrodes including nerve instead of muscle combinations during neurophysiological monitoring associated with surgical interventions to the spine have become more relevant for pediatric purposes, avoiding the anesthesiology-related influences. Observations on 280 patients with Lenke A-C types of spine curvature are presented before and after the surgical correction. Results: The MEPs recorded from nerves do not undergo fluctuations at different stages of scoliosis corrections and the anesthesia effect more than MEPs recorded from muscles. The use of non-invasive surface electrodes during neuromonitoring for MEP recordings shortens the total time of the surgical procedure without diminishing the precision of the neural transmission evaluation. The quality of MEP recordings during intraoperative neuromonitoring from muscles can be significantly influenced by the depth of anesthesia or administration of muscle relaxants but not those recorded from nerves. Conclusions: The proposed definition of "real-time" neuromonitoring comprises the immediate warning from a neurophysiologist about the changes in a patient's neurological status during scoliosis surgery (especially during pedicle screws' implantation, corrective rods' implantation, correction, distraction and derotation of the spine curvature) exactly during the successive steps of corrective procedures. This is possible due to the simultaneous observation of MEP recordings and a camera image of the surgical field. This procedure clearly increases safety and limits financial claims resulting from possible complications.

Motor evoked potentials recorded from muscles versus nerves after lumbar stimulation in healthy subjects and patients with disc-root conflicts.

OBJECTIVE: The study aimed to describe properties and to prove diagnostic usefulness of motor evoked potentials (MEPs) recordings from muscles versus nerves of lower extremities when induced at lumbar levels with magnetic field. METHODS: Methodologically similar MEPs recordings from muscles and nerves of lower extremities were performed once in healthy volunteers (N = 43) and patients with disc-root conflicts at lumbar spine levels (N = 43, proven in MRI studies). Simultaneous electroneurographic (ENG) recordings following stimulation of peroneal nerves verified neural impulses transmission in motor fibers peripherally and at L5 ventral roots. RESULTS: ENG studies in patients proven only moderate axonal type of peroneal nerves injury. The mean values of MEPs amplitudes recorded from nerves were significantly different from those recorded in anatomically related muscles, both in controls (1179.6 ± 451.2 vs 1718.3 ± 481.3) and patients (495.6 ± 275.9 vs 1218.2 ± 465.5) (p = 0.0009-0.0000012); they are about 30% and 51% smaller, respectively. In both groups of subjects, latencies of MEPs recorded from nerves were shorter at about 3.0 ms and characterized by a slightly longer duration (3.0-5.0 ms) than those recorded from muscles. Results revealed positive correlations between decrease of amplitudes in sEMG and MEPs recordings from lower extremities muscles indicating consequences of pathology in neural transmission from spinal centers. CONCLUSIONS: Results of this study point to clear-cut characteristics of MEPs induced oververtebrally with the magnetic field in parameters recorded in healthy subjects and patients with consequences of chronic L4-L5 low back pain, which can be easily implemented in clinical practice. Non-invasive method of MEPs recorded from nerves can be helpful for diagnosing of patients with visible atrophic changes in muscles and simultaneous symptoms of only slight pathology in transmission of nerve impulses peripherally.