Medial Antebrachial Cutaneous Nerve Injury After Brachial Plexus Block: Two Case Reports
A 30-year-old female patient was treated in the Department of Anesthesiology of this hospital for pain and numbness in the right medial antebrachial region that had begun 8 weeks earlier. She was referred to the Department of Rehabilitation for electrodiagnostic examinations. She had been receiving conservative treatment for an enchondroma following a fracture of the third proximal phalanx of her right hand suffered 6 months earlier during a fall. She had undergone curettage and a bone graft under ultrasound-guided axillary brachial plexus block 8 weeks prior to the present visit. She experienced numbness in the right medial antebrachial region immediately after the surgery. Her past medical history was unremarkable. Physical examinations revealed no particular finding other than decreased sensation and numbness of the right medial antebrachial region. According to the electrodiagnostic examinations conducted 8 weeks after onset, the median nerve and the ulnar nerve were both normal in motor nerve conduction studies. In sensory nerve conduction studies, the latency of the right median nerve was 1.80 ms and 1.95 ms on the unaffected left side. The amplitude on the right side was 8.6 µV, showing a slight reduction compared to the left side (10.6 µV), although the difference was not clinically significant (). In needle electromyography, no abnormal spontaneous activities were observed in the muscles innervated by the median nerve or in the ulnar nerve of the right-hand region.\nBased on the results of the physical examinations and the electrodiagnostic examinations, right MABC nerve injury was suspected. Pregabalin 75 mg, clonazepam 0.5 mg, and tramadol 50 mg were orally administered, and stellate ganglion block was performed. However, the treatment did not relieve the patient's symptoms. In follow-up sensory nerve conduction study of the right MABC nerve 13 weeks after the onset of the symptoms, the amplitude had increased slightly to 10.6 µV, and the patient reported that the numbness and pain in the right medial antebrachial region were considerably relieved. In the somatosensory evoked potential, the N20 latency of the MABC nerve on the right side was 16.80 ms and 15.90 ms on the left side. The N20-P25 amplitude on the right side was 1.30 µV and 1.56 µV on the left side ().