Swift T R, Leshner R T, Gross J A
Neurology. 1980 Apr;30(4):339-44. doi: 10.1212/wnl.30.4.339.
Arm-diaphragm synkinesis may occur after injury to the proximal portion of the brachial plexus or cervical nerve roots. Regenerating axons of phrenic motor neurons are misdirected to supply limb muscles. Electrodiagnostic investigations of three patients with symptoms referable to upper brachial plexus or cervical roots revealed motor units in either biceps or triceps muscles that discharged during inspiration. These units did not fire during forced or passive expiration or Valsalva maneuver. Activation of these units could not be achieved by volitional contraction of the appropriate arm muscles. The synkinetic motor units were of increased amplitude and duration. Some units contained late components that demonstrated jitter and blocking, as is characteristic of reinnervated motor units. The unwary electromyographer may misinterpret these synkinetic units as incomplete muscle relaxation or some form of abnormal repetitive discharge. Correct identification of these units provides objective evidence of antecedent nerve root or brachial plexus injury.
臂膈协同运动可能发生在臂丛神经近端或颈神经根损伤后。膈运动神经元的再生轴突被错误导向，以支配肢体肌肉。对三名有上臂丛神经或颈神经根症状患者的电诊断检查发现，在吸气时，肱二头肌或肱三头肌中有运动单位放电。在用力呼气、被动呼气或瓦尔萨尔瓦动作期间，这些运动单位不放电。通过适当的手臂肌肉随意收缩无法激活这些运动单位。协同运动的运动单位振幅和持续时间增加。一些运动单位包含晚期成分，表现出颤抖和阻滞，这是再支配运动单位的特征。粗心的肌电图检查人员可能会将这些协同运动单位误判为肌肉放松不完全或某种形式的异常重复放电。正确识别这些运动单位可提供先前神经根或臂丛神经损伤的客观证据。
