Spinal Surgery Case Report 1 A Surgical Case of Entrapment Neuropathy of the Median Nerve in the Proximal Forearm Tetsur

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1 Spinal Surgery Case Report 1 A Surgical Case of Entrapment Neuropathy of the Median Nerve in the Proximal Forearm Tetsuryu Mitsuyama, M.D., Shigekuni Tachibana, M.D., Toshiyuki Sasaki, M.D., Masahito Yuzurihara, M.D., Motoo Kubota, M.D., Takaomi Taira, M.D., Yoshikazu Okada, M.D. Abstract Entrapment neuropathy of the median nerve in the proximal forearm is comparatively rare. Lacertus fibrosus, pronator teres, and arcade of the flexor digitorum superficialis are possible sites of entrapment. We report the case of a patient with entrapment neuropathy of the median nerve in the proximal forearm he was appropriately diagnosed and was treated successfully. A 66 year old man had become unable to turn a key or count bills with his right hand for several months. The symptoms had started 1 month after the beginning of hemodialysis treatment because of diabetic nephropathy. He presented with sensory disturbance on the median nerve territory of both hands and motor weakness in the right flexor pollicis longus, flexor digitorum profundus, and pronator quadratus. Tinel s sign was not present in the wrist however, Phalen s test was positive in the right hand. He was unable to make a round ring with the right thumb and the forefinger. Flexion of the middle finger with resistance caused a reproducible pain in the proximal forearm, suggesting entrapment at the arcade of the flexor digitorum superficialis. Entrapment neuropathy of the median nerve in the right proximal forearm, including the anterior interosseous nerve was established. He underwent surgical decompression of the median nerve at both the right carpal tunnel and proximal forearm. Immediately after the decompression and severing of the fibrous aponeurosis of the flexor digitorum superficialis muscle, the patient could achieve full flexion of the distal joints of the right thumb and forefinger. All of his complaints disappeared within 5 months of the surgery. A thorough understanding of both regional anatomy and pathophysiology is essential in diagnosis of median nerve entrapment in the proximal forearm. Simple classification by entrapment sites may be helpful in diagnosis and treatment. Tracing the median nerve from the proximal direction, a surgeon can expose the possible entrapment sites, which are the lacertus fibrosus, pronator teres, and flexor digitorum arcade, in anatomical sequence. Received August 2, 2013 accepted January 6, 2014 Key words anterior interosseous nerve, arcade of the flexor digitorum superficialis muscle, median nerve entrapment, proximal forearm, tear drop sign Address reprint requests to Tetsuryu Mitsuyama, M.D., Department of Neurosurgery, Tokyo Women s Medical University, 8 1 Kawada cho, Shinjuku ku, Tokyo , Japan 2

b A photograph of the hands 5 months after surgery. Showing the Patient can form a round circle with the right thumb and index finger.

2 a b Fig. 1 a A preoperative photograph of hands, showing the inability to form a round circle with the right thumb and index finger due to paresis of the flexor pollicis longus and flexor digitorum profundus. b A photograph of the hands 5 months after surgery. Showing the Patient can form a round circle with the right thumb and index finger. Table 1 Nerve conduction studies Motor nerve conduction study Nerve Rt. median Lt. median Rt. ulnar Lt. ulnar Amplitude mv Sensory nerve conduction study Nerve Rt. median Lt. median Rt. ulnar Lt. ulnar Amplitude V W E NCV m s W F NCV m s Distal latency ms NCV nerve conduction velocity, W E Wrist Elbow, W F Wrist Finger / MRI / ml 2 4 Tinel Phalen MMT MMT tear drop sign 1 Fig. 1 W Table 1 W

pain site by resisted flexion of the middle finger, and another skin incision for carpal tunnel release.

superficial layer. c Pronator teres muscle is exposed by severing the lacertus fibrosus.

muscle. e Distal dissection of the median nerve.

g Decompression of the median nerve by severing the fibrous aponeurosis of the flexor digitorum superficialis

h Illustration shows the anterior interosseous nerve arising from the main trunk of the medial nerve just

i Complete recovery of thumb and index finger movements just after the decompression.

の低下を認めた両側の正中神経では終末潜時の延長と得られた手関節での Tinel 徴候は認めなかったが誘発手関節以遠での著明な伝導速度の低下を認めたまた試験である Phalen

3 b a c d f e g i h Fig. 2 Intraoperative photographs a A curved skin incision on the proximal forearm surrounding the reproducible pain site by resisted flexion of the middle finger, and another skin incision for carpal tunnel release. b Lacertus fibrosus, an aponeurosis of the biceps brachii muscle, is identified after the dissection of the superficial layer. c Pronator teres muscle is exposed by severing the lacertus fibrosus. d Proximal part of the median nerve and the brachial artery are identified by retracting the pronator teres muscle. e Distal dissection of the median nerve. f Entrapment of the median nerve at the arcade of the flexor digitorum superficialis muscle. g Decompression of the median nerve by severing the fibrous aponeurosis of the flexor digitorum superficialis muscle. h Illustration shows the anterior interosseous nerve arising from the main trunk of the medial nerve just distal to the flexor digitorum arcade. i Complete recovery of thumb and index finger movements just after the decompression. も順行性検査では検出されず逆行性検査でのみ検出さを支持する所見が得られたなお糖尿病性多発神経障れたいずれも活動電位は低振幅であり神経伝導速度害と両側手関節での正中神経障害を示唆する検査結果もの低下を認めた両側の正中神経では終末潜時の延長と得られた手関節での Tinel 徴候は認めなかったが誘発手関節以遠での著明な伝導速度の低下を認めたまた試験である Phalen 徴候の陽性所見と末W神経伝導検査右正中神経で肘手関節間に明らかな伝導速度の低下をの結果から右手根管での絞扼性正中神経障害も合併し認めたている可能性があると診断した 6 カ月以上経過しても誘発試験抵抗を加えた右中指屈曲により前腕近位部診運動障害の改善を認めずむしろ悪化していたため発症 9 カ月目に局所麻酔下に手術治療を実施した同一術での疼痛の誘発を認めた断手関節以遠の正中神経領域の感覚障害と母野で短時間に手術が行えることならびに誘発検査や電指示指のピンチ動作の障害から前骨間神経分岐部を気生理検査で手根管での絞扼性正中神経障害を示唆する含む右前腕近位部での絞扼性正中神経障害と診断した所見が得られたことから前腕近位部だけでなく手根管抵抗を加えた右中指屈曲により前腕近位部での疼痛が誘部でも右正中神経の絞扼解除術を同時に実施した発されることから絞扼部位を浅指屈筋アーチと診断したまた電気生理学的にも右前腕部での正中神経障害脊髄外科手術まずは右手根管開放術を行った次いで右前腕近位部における正中神経の絞扼解除術を実施した VOL. 28 NO 年 4 月 59

4 Fig. 2 W / 1 5 Fig. 1Phalen 4,5 4,6 4,5 Table 2 Proposed classification of entrapment neuropathy of the median nerve in the proximal forearm 1 Bicipital aponeurosis lacertus fibrosus 2 Pronator teres muscle between the humeral head tendon and the ulnar head tendon 3 The arcade of the flexor digitorum superficial muscle 4 Others 5 8 cm 6 5, Table 2 Spinner Fig. 3 4,6 4,6 2 Table 2 8 a b c Fig. 3 Provocative tests for median nerve entrapment in the proximal forearm Reproduced with permission of the copyright owner 5 a Pain in the proximal forearm provoked by resistance to forearm pronation and wrist flexion suggesting entrapment at the pronator teres muscle. b Pain caused by resisting to forearm supination and elbow flexion suggesting entrapment at the lacertus fibrosus. c Pain by resistance to flexion of the middle finger suggesting entrapment at the arcade of the flexor digitorum superficialis muscle.

7,9 7 9 7,9 7 Phalen multiple crush syndrome 4 20 11 W W 6 Fig.

5 7, ,9 7 Phalen multiple crush syndrome W W 6 Fig. 4 A tear drop sign Classic response of a right hand affected by anterior interosseous nerve palsy. Note the extension of the index finger distal interphalangeal joint and thumb interphalangeal joint tear drop sign Fig Ulrich

6 Tinel Phalen 1Lee MJ, LaStayo PC Pronator syndrome and other nerve compressions that mimic carpal tunnel syndrome. J Orthop Sports Phys Ther , Gross PT, Tolomeo EA Proximal median neuropathies. Neurol Clin , Ulrich D, Piatkowski A, Pallua N Anterior interosseous nerve syndrome retrospective analysis of 14 patients. Arch Orthop Trauma Surg , Mackinnon SE, Dellon AL Median nerve entrapment in the proximal forearm and brachium. in Mackinnon SE, Dellon AL edssurgery of the Peripheral Nerve, New York, Thieme Medical Publishers, 1988, pp W 1997 pp Spinner M The median nerve. in Spinner M edinjuries to the Major Branches of Peripheral Nerves of the Forearm 2 nd edition, Philladelphia, W. B. Saunders, 1979, pp W B Wb Entrapment neuropathy 65 Suppl Ochi K, Horiuchi Y, Tazaki K, et al Surgical treatment of spontaneous anterior interosseous nerve palsy a comparison between minimal incision surgery and wide incision surgery. J Plast Surg Hand Surg , Liveson JA Localized Process, Peripheral Neurology Case Studies 3 rd edition, New York, Oxford University Press, 2000, pp Dellon AL Treatment of symptomatic diabetic neuropathy by surgical decompression of multiple peripheral nerves. Plast Reconstr Surg , CTS

臨床神経 indd

臨床神経 indd 164 41 3 CTS CTS Key Words : carpal tunnel syndrome, nerve conduction study, sensory nerve action potential CTS CTS 10 1 2 CTS 1 3 4 CTS 1 Tinel Phalen Tinel CTS 1 Phalen Phalen Phalen Phalen 2 1/3 : 1