Nilsson J, Panizza M, Roth B J, Basser P J, Cohen L G, Caruso G, Hallett M
Laboratory of Clinical Neurophysiology, Fondazione Clinica del Lavoro, Castel Goffredo, (MN) Italy.
Electroencephalogr Clin Neurophysiol. 1992 Aug;85(4):253-64. doi: 10.1016/0168-5597(92)90114-q.
Magnetic stimulation has not been routinely used for studies of peripheral nerve conduction primarily because of uncertainty about the location of the stimulation site. We performed several experiments to locate the site of nerve stimulation. Uniform latency shifts, similar to those that can be obtained during electrical stimulation, were observed when a magnetic coil was moved along the median nerve in the region of the elbow, thereby ensuring that the properties of the nerve and surrounding volume conductor were uniform. By evoking muscle responses both electrically and magnetically and matching their latencies, amplitudes and shapes, the site of stimulation was determined to be 3.0 +/- 0.5 cm from the center of an 8-shaped coil toward the coil handle. When the polarity of the current was reversed by rotating the coil, the latency of the evoked response shifted by 0.65 +/- 0.05 msec, which implies that the site of stimulation was displaced 4.1 +/- 0.5 cm. Additional evidence of cathode- and anode-like behavior during magnetic stimulation comes from observations of preferential activation of motor responses over H-reflexes with stimulation of a distal site, and of preferential activation of H-reflexes over motor responses with stimulation of a proximal site. Analogous behavior is observed with electrical stimulation. These experiments were motivated by, and are qualitatively consistent with, a mathematical model of magnetic stimulation of an axon.
磁刺激尚未常规用于外周神经传导研究，主要是因为刺激部位的位置不确定。我们进行了多项实验来确定神经刺激部位。当一个磁线圈沿着肘部区域的正中神经移动时，观察到了与电刺激时类似的均匀潜伏期变化，从而确保神经和周围容积导体的特性是均匀的。通过电刺激和磁刺激诱发肌肉反应并匹配它们的潜伏期、振幅和形状，确定刺激部位距离8字形线圈中心向线圈手柄方向为3.0±0.5厘米。当通过旋转线圈使电流极性反转时，诱发反应的潜伏期偏移了0.65±0.05毫秒，这意味着刺激部位移位了4.1±0.5厘米。磁刺激过程中类似阴极和阳极行为的其他证据来自于观察到在刺激远端部位时运动反应比H反射优先激活，以及在刺激近端部位时H反射比运动反应优先激活。电刺激时也观察到了类似行为。这些实验是由轴突磁刺激的数学模型推动的，并且在定性上与该模型一致。
