Ultrasound Identification of an Atypical Course of the Deep Branch of the Radial Nerve Passing Through the Proximal Interosseous Space: A Case Report.

We report an atypical course of the deep branch of the radial nerve (DBRN) identified through ultrasound (US) in a patient with persistent right medial elbow pain. During the US examination, an anatomical variation was observed, in which the DBRN deviated medially to pass through the proximal interosseous space between the radius and ulna, rather than following its typical path into the supinator muscle. This variation, observed only on the right limb, was asymptomatic but associated with a slight reduction in the extensor muscle bulk, suggesting a subclinical impact on the nerve.