Aging influences central motor conduction less than peripheral motor conduction: A transcranial magnetic stimulation study

Abstract

In this study we investigated the effects of aging on corticospinal tract conduction by measuring the corticoconus motor conduction time (CCCT). Motor evoked potentials were recorded from the right tibialis anterior muscle in 100 healthy volunteers. To activate the most proximal part of the cauda equina, magnetic stimulation was performed using a MATS coil over the L1 spinous process (L1-level latency). Transcranial magnetic stimulation of the motor cortex was also conducted (cortical latency). To obtain the CCCT, the L1-level latency was subtracted from the cortical latency. Age was significantly correlated with L1-level latency, but it was not significantly correlated with CCCT. CCCT is the most direct indicator of corticospinal tract conduction, whereas L1-level latency reflects whole peripheral motor conduction. Central motor conduction was found to be relatively less affected by aging compared with peripheral motor conduction.