Department of Neurology, Teikyo University School of Medicine, Tokyo, Japan.
Department of Medical Service, Aizen Hospital, Hokkaido, Japan.
Muscle Nerve. 2021 Jan;63(1):89-95. doi: 10.1002/mus.27082. Epub 2020 Oct 18.
We previously reported a new quantitative analysis of single-channel surface electromyography (EMG), the "clustering index method" (CI method), in the tibialis anterior muscle, which achieved sufficiently good sensitivity to detect neurogenic or myogenic abnormalities. The window width is a fundamental parameter of the CI method, and was arbitrarily set at 15 ms in that study. In this study, we searched for the most appropriate window width using expanded patient data. The data from our previous study were reanalyzed, and new patients were enrolled. Window width in the CI method was changed from 5 to 27.5 ms with a step of 2.5 ms. For each window width, Z-score values of individual subjects were calculated and the diagnostic yield was investigated. We enrolled 67 controls, 29 subjects with neurogenic disorders, and 39 with myogenic disorders. When the window width was set at 22.5 ms, the highest sensitivity was achieved both for neurogenic (97%) and myogenic (72%) disorders, with a specificity of 97%. Seven of 10 patients with inclusion body myositis were also abnormal. Reliable results were obtained by collecting 15 epochs per subject. There are two conflicting effects that appear to be best balanced at a window width of 22.5 ms: a wider width decreases the chance that a motor unit potential (MUP) is divided into two adjacent windows, and a narrower width reduces the possibility that an MUP firing at a low-frequency is counted twice by the differential sequences. CI is promising as a non-invasive method to diagnose neuromuscular disorders.
我们之前报道了一种新的单通道表面肌电图（EMG）定量分析方法，即“聚类指数法”（CI 法），该方法在前胫骨肌中具有足够高的灵敏度，可以检测出神经源性或肌源性异常。窗口宽度是 CI 法的一个基本参数，在之前的研究中被任意设置为 15ms。在这项研究中，我们使用扩展的患者数据来寻找最合适的窗口宽度。重新分析了之前研究的数据，并招募了新的患者。CI 法的窗口宽度从 5 到 27.5ms 以 2.5ms 的步长进行改变。对于每个窗口宽度，计算个体受试者的 Z 分数值，并研究诊断效果。我们纳入了 67 名对照者、29 名神经源性疾病患者和 39 名肌源性疾病患者。当窗口宽度设置为 22.5ms 时，对于神经源性（97%）和肌源性（72%）疾病都达到了最高的灵敏度，特异性为 97%。10 名包涵体肌炎患者中有 7 名也异常。通过每个受试者收集 15 个时程，获得了可靠的结果。在窗口宽度为 22.5ms 时，似乎出现了两种相互冲突的效果，达到了最佳平衡：较宽的宽度降低了运动单位电位（MUP）被分成两个相邻窗口的可能性，较窄的宽度减少了低频 MUP 被差分序列两次计数的可能性。CI 作为一种非侵入性方法来诊断神经肌肉疾病是有前途的。
