NEJM临床医学影像]：用冰袋诊断重症肌无力 2016-11-21 CSCCM Images in Clinical Medicine Diagnosing Myasthenia Gravis with an Ice Pack Wendy W. Liu, Adam Chen N Engl J Med 2016; 375: e39 DOI: 10.1056/NEJMicm1509523 A 68-year-old man presented with unilateral ptosis and no other symptoms. The neurologic examination revealed ptosis of the left eye after a sustained upward gaze (Panel A). The movements of the extraocular muscles were normal. Myasthenia gravis was suspected, and the ice-pack test was performed with the placement of an instant cold pack over the left eye (Panel B). After 2 minutes, the ptosis was substantially diminished (>5 mm), indicating a positive test (Panel C). The diagnosis was further supported by the presence of serum anti–acetylcholine receptor antibodies and by electrodiagnostic testing, which showed a decremental response to repetitive nerve stimulation. The ice-pack test can be a useful bedside test to distinguish myasthenia gravis from other causes of ptosis or ophthalmoparesis. The inhibition of acetylcholinesterase activity at a reduced muscle temperature is thought to underlie the observed clinical improvement. The patient was treated symptomatically with pyridostigmine, and the ptosis was diminished. 一名68岁男性患者因一侧上睑下垂就诊，患者没有其他症状。神经系统检查发现，患者持续向上方凝视后左眼睑下垂（图A）。眼外肌运动正常。医生怀疑患者为重症肌无力，遂进行了冰袋试验，即将速冻冰袋置于左眼部位（图B）。2分钟后，眼睑下垂明显减轻(> 5 mm)，提示试验结果为阳性（图C）。进一步检查血清抗乙酰胆碱受体抗体结果为阳性，电生理诊断显示神经重复刺激反应递减，支持重症肌无力的诊断。冰袋试验是一种有用的床旁试验，用于鉴别重症肌无力及导致眼睑下垂或眼肌麻痹的其他病因。肌肉温度降低后，胆碱酯酶活性受到抑制，可能是临床表现改善的机制。患者使用吡啶斯的明对症治疗后，眼睑下垂得以缓解。