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

Abstract

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.

Comparison of Motor Evoked Potentials Neuromonitoring Following Pre- and Postoperative Transcranial Magnetic Stimulation and Intraoperative Electrical Stimulation in Patients Undergoing Surgical Correction of Idiopathic Scoliosis

“…The future of developing neuromonitoring methods with MEP recordings should consider not only non-invasive methods with surface electrodes, but also studies exploring the approach of nerve-versus muscle-recorded MEP [63]. These are particularly important, considering the "resistance" of nerve-recorded potentials to paralysis applied by anesthesiologists during the intraoperative neuromonitoring of spine surgeries [64].…”

“Real-Time Neuromonitoring” Increases the Safety and Non-Invasiveness and Shortens the Duration of Idiopathic Scoliosis Surgery

“…MEPs recorded from nerves appear stable enough to provide reliable information regarding the efferent neural conduction in patients with advanced neurogenic muscle changes. The recording of the evoked potential from above the nerve in the place of its anatomical course does not significantly interfere with the recording of the bioelectric activity of the contracting muscle, as shown by the research of Garasz et al [ 38 ]. Recording from the peroneal nerve to verify the overall efferent conduction of nerve impulses from the level of the upper motor neuron following TMS has also been successfully used in experimental studies to assess the effectiveness of the regeneration in nerve fibers [ 47 ].…”

“…The concept of recording the MEP from the nerve during neuromonitoring is mentioned by Gonzales et al [ 48 ], both following cortical stimulation as well as direct spinal cord stimulation. Among the known descriptions are motor evoked potentials recorded from nerves versus muscles following lumbar stimulation with the magnetic field in healthy subjects and patients with disc–root conflicts, provided by Garasz et al [ 38 ]. In their studies, like in this report, the mean values of the MEP amplitudes recorded from the nerves significantly differed from those recorded in anatomically related muscles in the controls and patients: they were about 30% and 51% smaller, respectively.…”

“…The MEP parameters were analyzed bilaterally in recordings from the tibialis anterior (TA) muscle or from above the surface of the peroneal (PER) nerve, lateral to the head of the fibula, in the place of their longitudinal, anatomical course. While the choice of recording from the TA muscle was dictated by the possibility of comparing the MEP parameters with the descriptions of other researchers monitoring the overall efferent conduction from the level of the upper motoneurone to the effector, recording from above the nerve surface is innovative, previously described in studies on small populations of patients with locomotor dysfunction as a consequence of disc–root conflicts [ 38 ] and scoliosis [ 8 ]. The aim of describing it in this paper is to provide a detailed presentation of an alternative intraoperative neuromonitoring method, which is possibly more resistant to the anesthesia agent’s influence than recording from the muscle.…”

“…However, the amplitude parameter of the MEP is likely to be sensitive to the deep anesthesia influence, and the conditions of the recordings preclude the use of the constant neuromuscular blockade. An interesting proposal that seems to resolve the above problems is recording from the lower-extremity nerves [ 37 ], when the amplitude parameters are approximately half as low as those recorded from the muscles [ 38 ] but can be stably recorded, regardless of the level of anesthesia [ 23 ].…”