Prognostic significance of motor evoked potentials in surgical interventions to eliminate spinal stenosis at the cervical level

Introduction. Transcranial electrical stimulation is a neurophysiological method that is used intraoperatively for evaluating the conduct of a nerve impulse through the cortical-spinal tract. However, the results obtained during registration of this modality do not always correlate with the neurological status of the patient after surgery.
The purpose of the study is to determine the prognostic significance of motor evoked potentials in surgical interventions for the elimination of spinal stenosis at the cervical level.
Materials and methods. The study analyzed the results of 20 microsurgical root decompressions at the cervical level by eliminating spinal stenosis. Surgical interventions were performed in the neurosurgical Department of National medical and surgical center named after N.I. Pirogov from august 2018 to march 2019. Intraoperatively there were used the following modalities: motor evoked potentials, 3-channel registration of somatosensory evoked potentials from the median nerves, 8-channel electroencephalography, and train-of-four monitoring. The patients were divided into 2 groups: in the 1st group was used inhalant anesthetics, in the 2nd the anesthesia was conducted according to the protocol “Total intravenous anesthesia”.
Results. Within each group, in a number of cases, there was a decrease in the response amplitude (by 80 % or more), as well as a loss of motor evoked potentials. In the “Total intravenous anesthesia” group, the current stimulation forces used to obtain motor evoked potentials did not exceed 150 mA, while in the group of inhaled anesthetics, the maximum value was 300 mA, and the average value was 170 mA. In the “Total intravenous anesthesia” group, in 2 cases, a loss of response from one myotome at the decompression phase was registered without recovery during intraoperation monitoring, in 2 cases there was the amplitude loss by 80 % or more with subsequent recovery. In the “Total intravenous anesthesia” group, the results were comparable.
Conclusion. During neurophysiological monitoring in surgeries at the cervical level, the loss of motor evoked potentials from one myotome, as well as a decrease the response amplitude by 80 % or more are doubtful as a criteria for predicting neurological deficit.

1. MacDonald D.B. Intraoperative motor evoked potential monitoring: overview and update. J Clin Monit Comput 2006;20:347–77. DOI: 10.1007/s10877-006-9033-0. PMID: 16832580.

2. Legatt A.D., Emerson R.G., Epstein C.M. et al. ACNS Guideline: transcranial electrical stimulation motor evoked potential monitoring. J Clin Neurophysiol 2016:33(1):42–50. DOI: 10.1097/WNP.0000000000000253. PMID: 26756258.

3. MacDonald D.B. Overview on Criteria for MEP Monitoring. J Clin Neurophysiol 2017:34(1):4–11. DOI: 10.1097/WNP.0000000000000302. PMID: 28045852.

4. Ushirozako H., Yoshida G., Hasegawa T. et al. Characteristics of false-positive alerts on transcranial motor evoked potential monitoring during pediatric scoliosis and adult spinal deformity surgery: an “anesthetic fade” phenomenon. J Neurosurg Spine 2019:22:1–9. DOI: 10.3171/2019.9.SPINE19814. PMID: 31756712.

5. Macdonald D.B., Stigsby B., Al Homoud I. et al. Utility of motor evoked potentials for intraoperative nerve root monitoring. J Clin Neurophysiol 2012;29(2):118–25. DOI: 10.1097/WNP.0b013e31824ceeaf. PMID: 22469675.

6. Traba A., Romero J.P., Arranz B. A new criterion for detection of radiculopathy based on motor evoked potentials and intraoperative nerve root monitoring. J Clin Neurophysiol 2018;129(10):2075–82. DOI: 10.1016/j.clinph.2018.07.005. PMID: 30077868.

7. Malcharek M.J., Loeffler S., Schiefer D. et al. Transcranial motor evoked potentials during anesthesia with desflurane versus propofol – A prospective randomized trial. J Clin Neurophysiol 2015;126(9):1825–32. DOI: 10.1016/j.clinph.2014.11.025. PMID: 25541524.

8. Langeloo D.D., Journée H.L., de Kleuver M. et al. Criteria for transcranial electrical motor evoked potential monitoring during spinal deformity surgery. A review and discussion of the literature. J Clin Neurophysiol 2007;37:431–9. DOI: 10.1016/j.neucli.2007.07.007. PMID: 18083499.

9. Abboud T., Schaper M., Dührsen L. et al. A novel threshold criterion in transcranial motor evoked potentials dring surgery for gliomas close to the motor pathway. J Neurosurg 2016;125:795–802. DOI: 10.3171/2015.8.JNS15143. PMID: 26799297.

10. Alexander R., Volpe N.G. Total Intravenous Anesthesia. In: Gullo A. (eds) Anaesthesia, Pain, Intensive Care and Emergency Medicine. Milano: A.P.I.C.E. Springer, 2002. DOI: 10.1007/978-88-470-2099-3_70.

11. Ali H.H., Savarese J. Monitoring of neuromuscular function. Anesthesiology 1976; 45(2):216–49. DOI: 10.1097/00000542-197608000-00009. PMID: 180849.

12. Leppanen R. Intraoperative monitoring of segmental spinal nerve root. J Clin Monit Comput 2005;19:437–61. DOI: 10.1007/s10877-005-0086-2. PMID: 16437295.

13. Каньшина Д.С., Кузнецов А.Н., Николаев С.Г. и др. Вариабельность представленности и латентности F-волны у пациентов в разные периоды позвоночно-спинномозговой травмы. Нервно-мышечные болезни 2019;9(1):61–6. [Kan’shina D.S., Kuznetsov A.N., Nikolaev S.G. et al. The variability of representation and latency of the F-wave in patients at different periods of spinal cord injury. Nervno-myshechnye bolezni = Neuromuscular Diseases 2019;9(1):61–6. (In Russ.)]. DOI: 10.17650/2222-8721-2019-9-1-00-00.

14. Chistyakov A.V., Soustiel J.F., Hafner H. et al. Motor and somatosensory conduction in cervical myelopathy and radiculopathy. Spine (Phila Pa 1976) 1995;20(19):2135–40. DOI: 10.1097/00007632-199510000-00012. PMID: 8588171.

15. Koarashi M. The clinical significance of the F-wave of upper limb on cervical myelopathy. Nihon Seikeigeka Gakkai Zasshi 1983;57(2):123–35. PMID: 6854108.

16. Deletis V., Sala F. Intraoperative neurophysiological monitoring of the spinal cord during spinal cord and spine surgery: a review focus on the corticospinal tracts. J Clin Neurophysiol 2008;119(2):248–64. DOI: 10.1016/j.clinph.2007.09.135. PMID: 18053764.