新たな尺骨神経障害のメカニズムが考えられた滑車上肘筋の1例

Another Mechanism of Ulnar Nerve Impairment Triggered by Contraction of Anconeus Epitrochlearis Muscle. Case Report

　滑車上肘筋による尺骨神経障害の原因は，肘屈曲時に伸長された筋腹による物理的な神経の圧迫とされているが，今回，同筋の筋収縮が尺骨神経刺激の主原因と考えられる症例を経験した．術中に滑車上肘筋以外に尺骨神経を絞扼する因子はなく，滑車上肘筋の電気刺激に伴う収縮により尺骨神経支配筋群の収縮が確認され，また病歴もこれを支持するものであった．滑車上肘筋を持つ若年者の動的因子による尺骨神経障害の一因として滑車上肘筋の収縮による神経刺激が示唆された．

　Contractions of the anconeus epitrochlearis muscle can act as a causative factor producing ulnar nerve inpairment.　We report a case in which contraction of the anconeus epitrochlearis muscle irritated the ulnar nerve and produced symptoms of nerve palsy.　The patient was a 60-year-old male with a history of working as a non-professional baseball pitcher for more than 30 years.　During his active pitching days he noticed numbness and weakness in the ulnar nerve distribution from the acceleration phase to the follow-through phase of every pitch, and he later developed cubital tunnel syndrome.　Electrical stimulation of the anconeus epitrochlearis muscle during surgery to relieve cubital tunnel syndrome triggered contraction of the flexor carpi ulnaris muscle and abductor digiti minimi muscle.　Symptoms of ulnar nerve palsy induced by movement of the upper limbs may be primarily attributeable to ulnar nerve irritation by contraction of the anconeus epitrochlearis muscle in young people who have this muscle.