October 2025 POCUS Case of the Month: Lung Ultrasound

At the level of the axillary artery, the brachial plexus has divided into three cords (medial, lateral, and posterior), which are named in relationship to the axillary artery. These three cords travel with the axillary artery within the axillary sheath. The musculocutaneous nerve, however, as a terminal branch of the lateral cord, travels separately and is NOT located inside the axillary sheath. Thus, it must be blocked separately from an axillary brachial plexus block. Assuming that a musculocutaneous nerve block has not been performed, we would not expect to see a motor block of the biceps muscle, and elbow flexion and forearm supination, as well as cutaneous sensation to the lateral forearm, would be intact.