Baslo M Baris, Deymeer Feza, Serdaroglu Piraye, Parman Yesim, Ozdemir Coskun, Cuttini Marina
Department of Neurology, Istanbul Faculty of Medicine, Istanbul University, 34390 Capa, Istanbul, Turkey.
Neuromuscul Disord. 2006 Jul;16(7):454-8. doi: 10.1016/j.nmd.2006.05.009. Epub 2006 Jun 30.
The decrement pattern at low rates of repetitive nerve stimulation in myasthenia gravis (MG) is characterized by a decrease of compound muscle action potential size within the first 4-5 responses. With subsequent stimuli, compound muscle action potential size either increases or does not change. Following an observation that the pattern of decrement might be different in patients with Lambert-Eaton myasthenic syndrome (LEMS), we retrospectively studied traces from eight LEMS patients and 14 patients with seropositive generalized MG, calculating decrement percent from first to fourth and from first to ninth compound muscle action potential. In the LEMS patients, compound muscle action potential amplitude decreased progressively from first to ninth stimulus at 2, 3 or 5Hz in all traces but one. In contrast, MG patients demonstrated the expected improvement after the initial decrement in all traces except one. In the evaluation of patients suspected of having myasthenia gravis, the finding of progressive decrement pattern at low rates of repetitive nerve stimulation may alert the electromyographer to the possibility of Lambert-Eaton syndrome and prompt the performance of further electrodiagnostic tests.
重症肌无力（MG）患者在低频重复神经刺激时的递减模式特点是，在前4 - 5次反应中复合肌肉动作电位大小会降低。随后的刺激中，复合肌肉动作电位大小要么增加，要么不变。在观察到兰伯特 - 伊顿肌无力综合征（LEMS）患者的递减模式可能有所不同后，我们回顾性研究了8例LEMS患者和14例血清学阳性的全身型MG患者的记录，计算从第一次到第四次以及从第一次到第九次复合肌肉动作电位的递减百分比。在LEMS患者中，除一条记录外，所有记录在2、3或5Hz频率下，复合肌肉动作电位幅度从第一次刺激到第九次刺激均逐渐降低。相比之下，MG患者除一条记录外，所有记录在最初递减后均出现预期的改善。在评估疑似重症肌无力的患者时，低频重复神经刺激时出现渐进性递减模式这一发现可能会提醒肌电图检查者注意兰伯特 - 伊顿综合征的可能性，并促使其进行进一步的电诊断测试。
