P 205. Cortico-conus motor conduction time (CCCT)

Objective To measure the conduction time from the motor cortex to the conus medullaris (cortico-conus motor conduction time, CCCT) for leg muscles using magnetic stimulation. Methods Motor evoked potentials (MEPs) were recorded from right tibialis anterior muscle in 100 healthy volunteers. To activate spinal nerves at the most proximal cauda equina level or at the conus medullaris level, magnetic stimulation was performed using a MATS coil. Transcranial magnetic stimulation of the motor cortex was also conducted to measure the cortical latency for the target muscle. To obtain the CCCT, the latency of MEPs to conus stimulation (conus latency) was subtracted from the cortical latency. Results MATS coil stimulation evoked reproducible MEPs in all subjects, yielding CCCT data for all studied tibialis anterior muscles. Conclusions MATS coil stimulation provides CCCT data for healthy subjects. This novel method is useful for evaluation of corticospinal tract conduction for leg muscles because no peripheral component affects the CCCT.