Superficial Sensitive Nerves of the Upper Limb: Anatomy, US Scanning Technique, and Pathology

Purpose: The aim of this study was to describe the potential role of high-resolution ultrasound (US) for the evaluation of superficial sensitive nerves of the arm and forearm.

Methods and Materials: After US-guided percutaneous latex injection, three cadaveric limbs were dissected to identify the course of the medial cutaneous nerve of the arm (MCNA) and the medial (MCNF), lateral (LCNF), and posterior (PCNF) cutaneous nerves of the forearm and determine whether US is able to localize these small nerves. A consecutive series of 11 patients who had sensory disturbances in the territory of the MCNA, MCNF, LCNF, and PCNF were examined with US using a 17-5 MHz transducer. One patient had prolonged arm compression by a plaster cast, three underwent a penetrating injury along the nerve course, and one had a history of repeated cannulations of elbow veins. The other six patients presented with symptoms of superficial neuropathy in the absence of any history of trauma.

Results: Cadaveric dissection confirmed that US-guided injections placed latex into and around the MCNA, MCNF, LCNF, and PCNF in all specimens. In 10 of 11 patients, US allowed detection of definite nerve abnormalities. Pathologic findings included four fusiform neuromas and/or fibrous encasement, three schwannomas, one neurofibroma, one intraneural ganglion cyst arising from the radiocarpal joint, and one mechanical instability at the elbow level.

Conclusion: High-resolution US can identify the MCNA, MCNF, LCNF, and PCNF and characterize their abnormalities, providing unique information about these small nerve branches.

Fig. 1 Medial cutaneous nerve of the arm (white arrowhead) and median cutaneous nerve of the forearm (black arrowhead).

Fig. 2 Ganglion cyst involving the medial cutaneous nerve of the forearm (MCNF).

Fig. 3 Schwannoma involving the medial cutaneous nerve of the arm (MCNA).

Fig. 4 Multiple neurofibromas at the level of the medial cutaneous nerve of the forearm (MCNF).