Preoperative diagnosis of the responsible level in CCM using CMAPs: comparison with SCEPs

Abstract

Study design:A retrospective study.Objective:To elucidate the correlation between compound muscle action potentials (CMAPs) amplitudes and responsible level of compressive cervical myelopathy (CCM), and the accuracy of level diagnosis by using CMAPs.Setting:This study was conducted at the Department of Orthopedic surgery, Yamaguchi University Graduate School of Medicine, Japan.Method:A total of 28 patients with CCM were investigated in this study. Erb's point-stimulated CMAPs were measured from deltoid, biceps, triceps in all patients as compared with 88 healthy subjects. We performed a level diagnosis on the basis of CMAPs amplitudes. We performed a level diagnosis on the basis of CMAPs amplitudes and using an index that measures the deviation of CMAPs amplitudes between triceps and deltoid or biceps.Results:Significant correlations between the mean CMAPs amplitudes and responsible level were showed for deltoid (6.82±2.33 mV) at C3/4 (P<0.01) and biceps (8.75±4.42 mV) at C4/5 (P=0.015). Despite considerable individual variability in CMAP amplitudes, there were correlations among CMAPs amplitudes for deltoid, biceps and triceps in the same individual. The sensitivity was 75.0%, specificity 75.0% in the index for diagnosis of C3/4. The sensitivity was 75.0%, specificity 66.7% in the index for diagnosis of C4/5.Conclusion:This study showed small CMAPs amplitudes in the deltoid indicated a C3/4 level of myelopathy and in biceps at the C4/5 level and could help exclude clinically silent cord compression and determine the surgical procedure to the suitable level of concern. © 2014 International Spinal Cord Society.