摘要To the Editor:A 66-year-old female complained of muscle weakness,numbness,and pain in her left shoulder and arm for 16 months,after which muscle atrophy and forearm swelling gradually developed.Before admission,she had been diagnosed with brachial plexus neuritis and received intravenous methylprednisolone with 500 mg for 3 days,followed by a tapering of oral prednisolone.However,she did not benefit much from the treatment.Her personal medical history and family history were not remarkable.The previous chest computed tomography (CT) scan and magnetic resonance imaging (MRI) scans of her brain,cervical spinal cord,and brachial plexus [Figure 1A] were not remarkable.Needle electromyography examination revealed the weakened motor unit recruitment with abnormal spontaneous activities,including positive sharp waves and fibrillations in the part of muscles innervated by left brachial plexus.The nerve conduction studies showed that compound muscle action potential and sensory nerve action potential amplitudes decreased greatly with prolonged distal latency in the muscles innervated by branches of left brachial plexus.This presentation was more readily visible in the inferior-trunk-innervated regions,such as ulnar-nerve-innervated muscles.Otherwise,the reduction of nerve conduction velocities was negligible.