Kaneko K, Kawai S, Fuchigami Y, Morita H, Ofuji A
Department of Orthopedic Surgery, University of Yamaguchi, School of Medicine, Japan.
Electroencephalogr Clin Neurophysiol. 1996 Dec;101(6):478-82. doi: 10.1016/s0013-4694(96)96021-x.
Evoked spinal cord potentials (ESCPs) from the cervical epidural space and motor evoked potentials (MEPs) from the hand muscles were recorded simultaneously in 6 subjects following transcranial magnetic stimulation in two different coil orientations on motor cortex. The onset latency of the MEPs was approximately 1 ms shorter when the induced current flowed in a latero-medial direction (L-M stimulation) on the motor cortex as compared to a postero-anterior direction (P-A stimulation). Hence, L-M stimulation elicited an earlier component of the ESCPs than that induced by P-A stimulation. During general anesthesia with Sevoflurane, only the first component of the ESCPs could be elicited routinely following L-M stimulation. In contrast, all components of the ESCPs were dramatically attenuated following P-A stimulation. Moreover, first component latency of the ESCPs induced by L-M stimulation was almost the same as that induced by transcranial anodal electrical stimulation. These results suggest that if the induced current following transcranial magnetic stimulation flows in a latero-medial direction on motor cortex, it preferentially stimulates the corticospinal tract non-synaptically (producing a D-wave). However, if the induced current flows in a postero-anterior direction, it preferentially stimulates the corticospinal tract trans-synaptically (producing I-waves). Therefore, the direction of magnetically induced current is crucial in determining corticospinal excitability in the human brain.
在6名受试者中，在运动皮层上以两种不同的线圈方向进行经颅磁刺激后，同时记录了颈段硬膜外间隙的诱发脊髓电位（ESCPs）和手部肌肉的运动诱发电位（MEPs）。与前后方向（P-A刺激）相比，当感应电流在运动皮层上从外侧流向内侧方向（L-M刺激）时，MEPs的起始潜伏期约短1毫秒。因此，L-M刺激比P-A刺激诱发的ESCPs更早出现成分。在七氟醚全身麻醉期间，L-M刺激后通常只能诱发ESCPs的第一个成分。相反，P-A刺激后ESCPs的所有成分都显著减弱。此外，L-M刺激诱发的ESCPs的第一个成分潜伏期与经颅阳极电刺激诱发的几乎相同。这些结果表明，如果经颅磁刺激后的感应电流在运动皮层上从外侧流向内侧方向，它优先非突触性地刺激皮质脊髓束（产生D波）。然而，如果感应电流从后向前方向流动，它优先经突触刺激皮质脊髓束（产生I波）。因此，磁诱导电流的方向在确定人脑皮质脊髓兴奋性方面至关重要。
