Normative Values of Transcranial Magnetic Stimulation-Evoked Parameters for Healthy Developing Children and Adolescents

Context: Normative data-containing transcranial magnetic stimulation (TMS) evoked parameters are essential for correctly interpreting healthy development and assessing neuroplastic changes in certain neurologic disorders. Aims: The aim is to investigate corticospinal pathways by applying TMS to healthy developing children and adolescents. Settings and Design: In this cross-sectional study, we measured TMS evoked parameters associated with cortical and spinal stimulation obtained from the four extremities of 46 healthy children and adolescents (21 boys and 25 girls; mean ± standard deviation age: 6.4 ± 1.2 years; range: 3.0–20.5 years). Statistical Analysis: Spearman's correlation coefficients were calculated for each variable (weight and height) as a function of motor evoked potential (MEP) response latency and central motor conduction time (CMCT). Pearson's Chi-square test was used to determine the inter-variable correlations. Results: Latencies of MEPs were correlated with age (P < 0.001, r = 0.6948) and height (P < 0.006, r = 0.7994). Amplitudes of active-state MEPs were significantly higher than those of resting-state MEPs associated with the upper and lower extremities. The mean values for active-state MEP latencies were lower than those for resting-state MEPs. The CMCT and magnitudes of latency jumps were calculated using reliable MEP data for children and adolescents. Additionally, the unresponsiveness rates were significantly higher for children aged below 7 years. Conclusion: The TMS evoked parameters investigated in this study are necessary to accurately assess corticospinal pathway development in healthy children and adolescents.