A Rare Cadaveric Case Report of the Median Nerve Passing Through the Brachialis Muscle

To describe a rare cadaveric topographical variation of the median nerve (MN) involving an atypical relationship with the brachialis muscle (BM). Such variations, although uncommon, may complicate surgical procedures, regional anesthesia, and imaging interpretation. This report documents a variation in which the MN traverses the BM without providing motor innervation.

During the routine dissection of the right upper limb of a 75-year-old male donated cadaver, a unilateral (right-sided) topographical variation of the MN was identified. The MN diverged from its usual close association with the brachial artery (BA) and followed a medial and posterior course toward the BM. Within the middle third of the arm, the nerve penetrated a macroscopically distinct bundle of BM fibers, traversed the muscle belly, and exited in its distal third. Distally, the MN resumed a superficial course, re-approached the BA, and continued normally through the cubital fossa. No motor or accessory branches from the MN to the BM were identified during its intramuscular course. The surrounding muscle fibers closely encircled the nerve along its intramuscular segment, indicating a restricted anatomical corridor. The musculocutaneous nerve, BA, and the remaining neurovascular structures followed their typical anatomical pathways.

This anatomical configuration may represent a potential anatomical substrate for proximal MN irritation or compression and may clinically resemble pronator teres syndrome. Awareness of such variants is important for clinicians evaluating MN neuropathies and for surgeons, anesthesiologists, and radiologists working in the anterior compartment of the arm.