左側橈神經病變合併廣泛性正相尖波：肌電圖疾病

正相尖波(positive sharp waves , PSWs)和顫波(fibrillations)為周邊神經病變中常見的肌電圖變化。而傳統上，它們也被認為具有相同的臨床意義。然而，在有些疾病中，我們只能記錄到正相尖波而無顫波的出現。此病例是個32歲的男性，轉介來本部之肌電檢查室接受檢查。其因三週前左肱骨骨折造成左腕下垂無力。理學檢查發現其左腕，左手手指之伸肌肌力強度為零，合併左手姆指背部有麻木感。除此之外，並無其他肢體肌肉無力之現象。常規上肢神經傳導檢查部分，左側橈淺神經之感覺神經電位振幅變小，正中神經和尺神經之檢查結果皆正常。在針極肌電檢查方面，左側之肱橈肌、橈側伸腕肌及總伸指肌等，出現明顯正相尖波和顫波，並且無自主性運動單元電位波。而左側肱三頭肌、肱二頭肌、三角肌、旋前圓肌、外展拇短肌、右三角肌、雙下肢脛骨前肌等，則都出現了正相尖波而無顫波。最後我們所下的診斷是“嚴重左側橈神經損傷”。但因為所有肌力“正常”之肌肉群皆呈現無合併顫波之正相尖波，而且由於這病患並無肌肉強直疾病或電解質異常，因此這病人符合所謂“肌電圖疾病(EMG disease)”。這種形式的正相尖波應該是因針極刺激了肌肉細胞不穩定之細胞膜所引起。根據過去之研究，這是可能是一種顯性遺傳之疾病。這病例之討論希望能提供肌電圖臨床檢查醫師做最正確的診斷。

關鍵字

肌電圖疾病；正相尖波；顫波

並列摘要

Positive sharp waves (PSW) and fibrillations are frequently seen together in a variety of neuromuscular diseases and share the same clinical significance. However, PSW alone are also reported to occur in myotonic disorders, periodic hypokalemic paralysis, and local muscle trauma. Our patient, a 32-year-old man, fractured his left humerus in a traffic accident 3 weeks prior to presentation. He was referred to our electrodiagnostic laboratory due to left wrist and hand drop. On physical examination, he was found to have grade 0 muscle power in his left wrist and finger extensors. There was numbness over the dorsal aspect of the first web of the left hand, and second and third fingers. He had no history of myotonic disorder or clinical evidence of myotonia. No metabolic abnormalities were found. Routine nerve conduction studies of the left upper limb were normal except for a small amplitude of SNAP of left radial superflcial sensory nerve. Needle EMG studies of the left brachioradialis, extensor carpi radialis, and extensor digitorum communis muscles showed massive PSW and fibrillation potential without volitional motor unit potential. However, the other limb muscles, including the right upper limb and bilateral lower limbs, all had diffuse PSW without fibrillation, as well as normal morphology of motor unit potential and full maximal recruitment. The final electrophysiological diagnosis of this patient was a severe left radial nerve lesion at arm level below the branch to triceps associated with “EMG disease”. The patient was considered to have EMG disease because the isolated PSW was not clinically significant. This type of PSW is most likely caused by a needle piercing an unstable muscle cell membrane. This had been reported in an autosomal dominant manner. It is important for clinic physicians to interpret PSW and fibrillation correctly so as to avoid erroneous diagnoses.

並列關鍵字

EMG disease ； positive sharp waves ； fibrillations

國際替代計量

左側橈神經病變合併廣泛性正相尖波：肌電圖疾病

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