Review Question - QID 219914

This 35-year-old patient exhibits symptoms suggesting radial tunnel syndrome and subsequently undergoes radial tunnel release. The radial nerve develops from the posterior cord of the brachial plexus (Answer 4; Illustration 2).

Radial tunnel syndrome is a compressive neuropathy of the posterior interosseous nerve (PIN) at the level of the proximal forearm. The five potential sites of compression are the proximal aponeurotic edge of the supinator (arcade of Frohse), the fibrous bands of the radiocapitellar joint, the radial recurrent vessels (the leash of Henry), the medial edge of the ECRB, and the distal edge of the supinator. The proximal aponeurotic edge of the supinator is the most common site of compression. Patients present with deep aching pain in the dorsal radial forearm and muscle weakness secondary to pain (classically with resisted long finger extension and supination). Electrodiagnostic studies typically are inconclusive; however, an injection into the radial tunnel that results in a PIN nerve palsy and relief of symptoms is diagnostic. Patients should undergo extensive nonoperative management for at least one year before surgical consideration, which includes surgical release.

Lawrence et al. published their clinical experience of 29 patients who underwent primary exploration and proximal decompression of the radial nerve. Based on the visual analog assessment, the results were: excellent 18/30 (60%), good 3/30 (10%), fair 4/30 (13%), and poor 5/30 (17%). All of the patients who had fair or poor outcomes had a secondary diagnosis associated with radial tunnel syndrome, such as cervical radiculopathy, mononeuritis, or lateral upper condyle avulsion fracture. The authors conclude that careful history and physical are necessary for primary diagnosis and identifying additional pathologies.

Lubahn and Cermak published a review article on uncommon nerve compression syndromes in the upper extremity. They reviewed the pertinent anatomy of the radial nerve from the posterior cord of the brachial plexus to the distal innervations of the superficial and deep radial nerve. The authors conclude that a careful history and physical are necessary in the diagnostic process. They also recommend extensive nonoperative management.

Wolf et al. published an updated review in 2023 regarding diagnosing and managing radial tunnel syndrome. The authors review the physical exam and diagnostic modalities available, concluding that electrodiagnostic studies have questionable positive predictive value and may not be effective clinically. The authors conclude that there is significant debate regarding the ideal treatment of radial tunnel syndrome. The efficacy of surgical decompression has conflicting results in the literature. They recommend conservative treatment, including steroid injections, for initial management.

Figures A and B show an intraoperative picture of a posterior interosseous nerve release, and Figure B shows the release of the superficial fibers of the supinator muscle. Illustration 1 shows an illustration of the anatomy of the radial tunnel. Illustration 2 shows a diagram of the anatomy of the brachial plexus.

Incorrect answers:
Answer 1: The lateral cord does not contribute to the radial nerve.
Answer 2: The anterior cord is not a described cord of the brachial plexus.
Answer 3: The anterior division does not contribute to the radial nerve.
Answer 5: The medial cord does not contribute to the radial nerve.