2014 年 28 巻 1 号 p. 57-62
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.
