Four suspected cases of functional radial nerve entrapment neuropathy favorably treated with ultrasound-guided radial nerve block in the proximal brachial region

Abstract

Although radial nerve compression syndrome in the proximal brachial region is rare, the author has experienced four cases of suspected radial nerve entrapment neuropathy in that region. All the patients complained of dull pain in the upper extremity region innervated by the radial nerve on flexion of their shoulder and elbow joints. They also had the following factors in common: 1) they had been treated for another neuropathy in the proximal aspect of the affected arm, 2) they had the same tender point in the axilla, where ultrasound examination revealed the radial nerve ran between the medial and lateral heads of the triceps brachii muscle, and 3) an ultrasound-guided nerve block at the tender point ameliorated the symptoms. The speculated mechanism of the nerve entrapment was that flexion of the shoulder and elbow caused traction on the radial nerve and stretching of the triceps brachii muscle, which then compressed the nerve against the humeral shaft. Additionally, the double crush syndrome was thought to be involved in the condition.