Magnetic stimulation of the lumbosacral vertebral column in children: normal values and possible sites of stimulation

Magnetic stimulation of the cauda equina in the spinal canal with a flat, large round coil

“…The mean values from the 30 subjects are presented in Table 2. The mean CECT was 3.7 ± 0.7 ms, which was similar to that reported previously (mean 3.5 ms or 3.3 ms) [7,8].…”

“…cauda equina) sometimes have clinical importance because they are long and are frequently affected by disorders. However, activation of the cauda equina in the spinal canal by a round coil has never been reported (the proximal part of the cauda equina in spinal canal can be activated by an eight-shaped coil) [1,7,8]. Herein, we describe that proximal and intermediate parts of the cauda equina can be activated reliably using the MATS coil.…”

“…A previous paper has described that some middle part of the cauda equina might be activated with an 8-shaped coil in healthy children [8]. However, in adult subjects, the mid-part has never been activated [7,8].…”

“…The CMAP latency to MATS coil stimulation was about 0.5 ms shorter than PMCT (the difference is about 2.0-2.5 cm if nerve conduction velocity is assumed to be 40-50 m/s), supporting the hypothesis that the L1 level MATS coil stimulation activates the cauda equina near the root exit zone from the conus medullaris. In both electrical and magnetic stimulations, the current might concentrate to the proximal part of the cauda equina (root exit zone from conus medullaris) [7,8,10,11]. Based on these arguments, we consider that the L1 level MATS coil stimulation activates the cauda equina at the root exit site from the conus medullaris.…”

“…However, in adult subjects, the mid-part has never been activated [7,8]. The failure of magnetic stimulation of the cauda equina at some mid-part in adults is explainable according to the concept that eddy current concentrates into intervertebral foramen but does not penetrate further into the cauda equina within the spinal canal [1,7].…”