An Unusual Musculoaponeurotic Slip of the Brachioradialis as a Potential Cause of Radial Nerve and Radial Recurrent Artery Compression.

Muscular variations in the distal arm and proximal forearm can significantly alter neurovascular relationships and predispose individuals to compressive neuropathies. This dissection report documents a previously unreported musculofascial variant with potential clinical and surgical relevance. During the routine dissection of the right distal arm of a 70-year-old male cadaver, an accessory musculoaponeurotic slip was identified. The structure originated from the deep surface of the brachioradialis (BR) and coursed medially to insert into the bicipital tendon (BT) of the biceps brachii (BB), just proximal to the radial tuberosity. It formed a well-defined arch overlying both the radial nerve (RN) and radial recurrent artery (RRA). The RN exhibited focal indentation and medial displacement at the crossing point, while the RRA was also partially compressed. No other anomalies were noted. This musculoaponeurotic variant differs from previously reported configurations involving the BR and BB, including the accessory brachioradialis muscle (aBR). The simultaneous compression of the RN and RRA by such a structure has not been previously described. Given its location in the operative field of anterior surgical approaches to the elbow, this variation has implications for both diagnosis and surgical planning. This case expands the spectrum of recognized morphological variants that may contribute to radial neuropathy. Awareness of such configurations is essential for clinicians evaluating unexplained RN symptoms and for surgeons performing anterior approaches to the elbow.