Department of Neurology, National Hospital for Neurology and Neurosurgery, London, UK.
Faculty of Brain Sciences, UCL Queen Square Institute of Neurology, London, UK.
Hosp Pract (1995). 2022 Dec;50(5):373-378. doi: 10.1080/21548331.2022.2125706. Epub 2022 Sep 19.
In centers which routinely perform single fiber electromyography (SFEMG) for suspected myasthenia gravis (MG), the additional benefit of other neurophysiologic investigations and the frequency of myasthenia mimics has not been ascertained. We aimed to illustrate the range of neurological and non-neurological myasthenia mimics referred for evaluation, and contrast features of their electrophysiologic evaluation with confirmed MG.
We reviewed all SFEMG studies performed at our center between 1 January 2018 and 31 December 2020. Patient demographics, clinical phenotype, antibody status and final diagnosis were recorded. Electrophysiologic findings were correlated with clinical features and sensitivity analyses performed.
A total of 528 SFEMG studies were performed, of which 213 (41%) were abnormal. A diagnosis of MG was made in 101 individuals, including 46 with ocular MG and 35 with seronegative disease. Compared to myasthenia mimics with an abnormal SFEMG, individuals with MG had higher median jitter (mean consecutive difference 61 μs vs. 42 μs, p < 0.001) and a greater percentage of abnormal pairs (61% vs. 33%, p < 0.001) on SFEMG. Repetitive nerve stimulation was abnormal in 27.1% of people with MG and was associated with a generalized clinical phenotype (OR 4.17; 95% CI 1.67-10.48). Thirteen (2%) individuals with MG had normal SFEMG, of whom 10 were in clinical remission. Functional neurological disorders, cranial nerve palsies, primary ocular disease and myopathy were frequent myasthenia mimics.
SFEMG can be abnormal in a number of myasthenia mimics, and routine nerve conduction studies and electromyography should always be undertaken. In centers where SFEMG is performed routinely for the investigation of suspected MG, extensive proximal repetitive nerve stimulation can be foregone without substantially affecting diagnostic evaluation. Normal SFEMG in those with confirmed myasthenia gravis may help indicate clinical remission.
在常规进行单纤维肌电图（SFEMG）检查以怀疑重症肌无力（MG）的中心，尚未确定其他神经生理检查的额外益处和肌无力模拟物的频率。我们旨在说明神经和非神经肌无力模拟物的范围，并与确诊的 MG 进行对比其电生理评估的特征。
我们回顾了 2018 年 1 月 1 日至 2020 年 12 月 31 日在我们中心进行的所有 SFEMG 研究。记录患者的人口统计学、临床表型、抗体状态和最终诊断。对电生理发现与临床特征进行相关性分析，并进行敏感性分析。
共进行了 528 次 SFEMG 检查，其中 213 次（41%）异常。101 人被诊断为 MG，包括 46 例眼肌型 MG 和 35 例血清阴性疾病。与 SFEMG 异常的肌无力模拟物相比，MG 患者的中位抖动值更高（连续差异均值 61μs 与 42μs，p<0.001），异常对的比例更高（61%与 33%，p<0.001）。27.1%的 MG 患者重复神经刺激异常，与广泛的临床表型相关（OR 4.17；95%CI 1.67-10.48）。13 例（2%）MG 患者的 SFEMG 正常，其中 10 例处于临床缓解期。功能性神经障碍、颅神经麻痹、原发性眼部疾病和肌病是常见的肌无力模拟物。
SFEMG 可能在许多肌无力模拟物中异常，应始终进行常规神经传导研究和肌电图检查。在常规进行 SFEMG 检查以怀疑 MG 的中心，可以省略广泛的近端重复神经刺激，而不会对诊断评估产生实质性影响。确诊 MG 患者的正常 SFEMG 可能有助于表明临床缓解。
