Age, Height, and Sex on Motor Evoked Potentials: Translational Data From a Large Italian Cohort in a Clinical Environment.

Mariagiovanna Cantone,Giuseppe Lanza,Rita Bella,Raffaele Ferri,Francesco Fisicaro,Giovanni Pennisi,Luisa Vinciguerra,Riccardo Ricceri,Valentina Puglisi,Carla Vagli,Vincenzo Di Lazzaro,Manuela Pennisi

doi:10.3389/fnhum.2019.00185

Abstract

IntroductionMotor evoked potentials (MEPs) to transcranial magnetic stimulation (TMS) are known to be susceptible to several sources of variability. However, conflicting evidences on individual characteristics in relatively small sample sizes have been reported. We investigated the effect of age, height, and sex on MEPs of the motor cortex and spinal roots in a large cohort.MethodsA total of 587 subjects clinically and neuroradiologically intact were included. MEPs were recorded during mild tonic contraction through a circular coil applied over the “hot spot” of the first dorsal interosseous and tibialis anterior muscles (TAs), bilaterally. Central motor conduction time (CMCT) was estimated as the difference between MEP cortical latency and the peripheral motor conduction time (PMCT) by cervical or lumbar magnetic stimulation. Peak-to-peak MEP amplitude to cortical stimulation and right-to-left difference of each parameter were also measured.ResultsAfter Bonferroni correction, general linear (multiple) regression analysis showed that both MEP cortical latency and PMCT at four limbs positively correlated with age and height. At lower limbs, an independent effect of sex on the same measures was also observed (with females showing smaller values than males). CMCT correlated with both age (negatively) and height (positively) when analyzed by a single regression; however, with a multiple regression analysis this significance disappeared, due to the correction for the multicollinearity within the dataset.ConclusionPhysical individual features need to be considered for a more accurate and meaningful MEPs interpretation. Both in clinical practice and in research setting, patients and controls should be matched for age, height, and sex.

Highlights

Motor evoked potentials (MEPs) to transcranial magnetic stimulation (TMS) are known to be susceptible to several sources of variability
When TMS is applied over primary motor cortex (M1), the cortex is activated through an electromagnetic induction, the impulses are transmitted along the cortico-spinal tract and peripheral nerves, so that a MEP can be recorded from a skeletal muscle using standard EMG surface electrodes
Subgroup-specific graphs for MEP cortical latency and peripheral motor conduction time (PMCT) at the four limbs are shown in Figures 2–9, which illustrate their correlation with height, for each muscle in each age subgroup, further subdivided by sex

Summary

Introduction

Motor evoked potentials (MEPs) to transcranial magnetic stimulation (TMS) are known to be susceptible to several sources of variability. Some physical variables (i.e., age, height, and sex) all showed to affect MEPs (Chu, 1989; Booth et al, 1991; Ghezzi et al, 1991; Furby et al, 1992; van der Kamp et al, 1996; Mills and Nithi, 1997), the samples studied are relatively small and conflicting evidences on the relationship between MEPs and individual characteristics have been reported. Several technical and procedural factors (such as the characteristics of the stimulator, the coil design, and other experimental conditions) make it difficult to obtain normative data and to compare those established by different laboratories

Methods

Results

Discussion

Conclusion