Abstract：
OBJECTIVE: Prolonged compound muscle action potential (CMAP) duration and preferential loss of myosin are considered the diagnostic hallmarks of critical illness myopathy (CIM); however, their correlation and prognostic values have not been studied. We aimed to investigate the correlation between CMAP duration and myosin loss and their effect on mortality by comparing between patients with CIM with and without myosin loss.
METHODS: We searched the Mayo Clinic Electromyography Laboratory databases (1986-2021) for patients diagnosed with CIM on the basis of prolonged distal CMAP durations (>15 msec in fibular motor nerve studies recording over the tibialis anterior or >8 msec in other motor nerves) and needle EMG findings compatible with myopathy. Electrodiagnostic studies were generally performed within 24 hours after weakness became noticeable. We included only patients who underwent muscle biopsy. Clinical, electrophysiologic, and myopathologic data were reviewed. We conducted myosin/actin ratio analysis when muscle tissue was available. We used the Fisher exact test for categorical data comparisons and the Mann-Whitney 2-tailed test for continuous data. We applied the Kaplan-Meier technique to analyze survival rates.
RESULTS: Twenty patients (13 female patients) were identified [median age at diagnosis of 62.5 years (range: 19-80 years)]. The median onset of weakness was 24 days (range: 1-128) from the first day of intensive care unit admission. Muscle biopsy showed myosin loss in 14 patients, 9 of whom had >50% of myofibers affected (high grade). Type 2 fiber atrophy was observed in 19 patients, 13 of whom also had myosin loss. Patients with myosin loss had higher frequency of steroid exposure (14 vs 3; p = 0.004); higher median number of necrotic fibers per low-power field (2.5 vs 1, p = 0.04); and longer median CMAP duration (msec) of fibular (13.4 vs 8.75, p = 0.02), tibial (10 vs 7.8, p = 0.01), and ulnar (11.1 vs 7.95, p = 0.002) nerves compared with those without. Only patients with high-grade myosin loss had reduced myosin/actin ratios (<1.7). Ten patients died during median follow-up of 3 months. The mortality rate was similar between patients with and without myosin loss. Patients with high-grade myosin loss had a lower overall survival rate than those with low-grade or no myosin loss, but this was not statistically significant (p = 0.05).
CONCLUSIONS: Myosin loss occurred in 70% of the patients with CIM with prolonged CMAP duration. Longer CMAP duration predicts myosin-loss pathology. The extent of myosin loss marginally correlates with the mortality rate. Our findings highlight the potential prognostic values of CMAP duration and myosin loss severity in predicting disease outcome.
METHODS: We searched the Mayo Clinic Electromyography Laboratory databases (1986-2021) for patients diagnosed with CIM on the basis of prolonged distal CMAP durations (>15 msec in fibular motor nerve studies recording over the tibialis anterior or >8 msec in other motor nerves) and needle EMG findings compatible with myopathy. Electrodiagnostic studies were generally performed within 24 hours after weakness became noticeable. We included only patients who underwent muscle biopsy. Clinical, electrophysiologic, and myopathologic data were reviewed. We conducted myosin/actin ratio analysis when muscle tissue was available. We used the Fisher exact test for categorical data comparisons and the Mann-Whitney 2-tailed test for continuous data. We applied the Kaplan-Meier technique to analyze survival rates.
RESULTS: Twenty patients (13 female patients) were identified [median age at diagnosis of 62.5 years (range: 19-80 years)]. The median onset of weakness was 24 days (range: 1-128) from the first day of intensive care unit admission. Muscle biopsy showed myosin loss in 14 patients, 9 of whom had >50% of myofibers affected (high grade). Type 2 fiber atrophy was observed in 19 patients, 13 of whom also had myosin loss. Patients with myosin loss had higher frequency of steroid exposure (14 vs 3; p = 0.004); higher median number of necrotic fibers per low-power field (2.5 vs 1, p = 0.04); and longer median CMAP duration (msec) of fibular (13.4 vs 8.75, p = 0.02), tibial (10 vs 7.8, p = 0.01), and ulnar (11.1 vs 7.95, p = 0.002) nerves compared with those without. Only patients with high-grade myosin loss had reduced myosin/actin ratios (<1.7). Ten patients died during median follow-up of 3 months. The mortality rate was similar between patients with and without myosin loss. Patients with high-grade myosin loss had a lower overall survival rate than those with low-grade or no myosin loss, but this was not statistically significant (p = 0.05).
CONCLUSIONS: Myosin loss occurred in 70% of the patients with CIM with prolonged CMAP duration. Longer CMAP duration predicts myosin-loss pathology. The extent of myosin loss marginally correlates with the mortality rate. Our findings highlight the potential prognostic values of CMAP duration and myosin loss severity in predicting disease outcome.
摘要：
目的：延长复合肌肉动作电位（CMAP）持续时间和肌球蛋白优先损失被认为是危重病肌病（CIM）的诊断标志；然而，它们的相关性和预后价值尚未研究。我们旨在通过比较有和没有肌球蛋白丢失的CIM患者之间的关系，研究CMAP持续时间与肌球蛋白丢失之间的相关性及其对死亡率的影响。
方法：我们搜索了MayoClinic肌电图实验室数据库（1986-2021年），以根据远端CMAP持续时间延长（腓骨运动神经研究记录胫骨前肌>15毫秒或其他运动神经>8毫秒）和与肌病相符的针肌电图发现诊断为CIM的患者。电诊断研究通常在虚弱变得明显后24小时内进行。我们仅包括接受肌肉活检的患者。临床,电生理,和肌病理学数据进行了审查。当肌肉组织可用时，我们进行了肌球蛋白/肌动蛋白比率分析。我们使用Fisher精确检验进行分类数据比较，使用Mann-Whitney2尾检验进行连续数据比较。我们应用Kaplan-Meier技术分析生存率。
结果：确定了20例患者（13例女性患者）[诊断时的中位年龄为62.5岁（范围：19-80岁）]。从重症监护病房入院的第一天起，出现无力的中位数为24天（范围：1-128）。肌肉活检显示14例患者肌球蛋白丢失，其中9名肌纤维>50%受影响(高等级)。在19例患者中观察到2型纤维萎缩，其中13人也有肌球蛋白损失。肌球蛋白丢失患者的类固醇暴露频率较高（14vs3；p=0.004）；每个低功率区域的坏死纤维中位数较高（2.5vs1，p=0.04）；腓骨的CMAP中位持续时间（毫秒）较长（13.4vs8.75，p=0.02），胫骨（10vs7.8，p=0.01），尺神经（11.1vs7.95，p=0.002）与无尺神经相比。只有高度肌球蛋白丢失的患者肌球蛋白/肌动蛋白比率降低（<1.7）。10例患者在3个月的中位随访期间死亡。有和没有肌球蛋白丢失的患者的死亡率相似。高度肌球蛋白丢失的患者的总体生存率低于低度或无肌球蛋白丢失的患者，但这没有统计学意义（p=0.05）。
结论：在CMAP持续时间延长的CIM患者中，有70%发生肌球蛋白丢失。较长的CMAP持续时间预测肌球蛋白丢失病理。肌球蛋白损失的程度与死亡率略有相关。我们的发现强调了CMAP持续时间和肌球蛋白丢失严重程度在预测疾病预后方面的潜在预后价值。
方法：我们搜索了MayoClinic肌电图实验室数据库（1986-2021年），以根据远端CMAP持续时间延长（腓骨运动神经研究记录胫骨前肌>15毫秒或其他运动神经>8毫秒）和与肌病相符的针肌电图发现诊断为CIM的患者。电诊断研究通常在虚弱变得明显后24小时内进行。我们仅包括接受肌肉活检的患者。临床,电生理,和肌病理学数据进行了审查。当肌肉组织可用时，我们进行了肌球蛋白/肌动蛋白比率分析。我们使用Fisher精确检验进行分类数据比较，使用Mann-Whitney2尾检验进行连续数据比较。我们应用Kaplan-Meier技术分析生存率。
结果：确定了20例患者（13例女性患者）[诊断时的中位年龄为62.5岁（范围：19-80岁）]。从重症监护病房入院的第一天起，出现无力的中位数为24天（范围：1-128）。肌肉活检显示14例患者肌球蛋白丢失，其中9名肌纤维>50%受影响(高等级)。在19例患者中观察到2型纤维萎缩，其中13人也有肌球蛋白损失。肌球蛋白丢失患者的类固醇暴露频率较高（14vs3；p=0.004）；每个低功率区域的坏死纤维中位数较高（2.5vs1，p=0.04）；腓骨的CMAP中位持续时间（毫秒）较长（13.4vs8.75，p=0.02），胫骨（10vs7.8，p=0.01），尺神经（11.1vs7.95，p=0.002）与无尺神经相比。只有高度肌球蛋白丢失的患者肌球蛋白/肌动蛋白比率降低（<1.7）。10例患者在3个月的中位随访期间死亡。有和没有肌球蛋白丢失的患者的死亡率相似。高度肌球蛋白丢失的患者的总体生存率低于低度或无肌球蛋白丢失的患者，但这没有统计学意义（p=0.05）。
结论：在CMAP持续时间延长的CIM患者中，有70%发生肌球蛋白丢失。较长的CMAP持续时间预测肌球蛋白丢失病理。肌球蛋白损失的程度与死亡率略有相关。我们的发现强调了CMAP持续时间和肌球蛋白丢失严重程度在预测疾病预后方面的潜在预后价值。
