Musculocutaneous nerve
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What it means
Lateral cord of the brachial plexus (C5–C7). Pierces coracobrachialis; supplies the anterior (flexor) compartment of the arm — biceps brachii, brachialis, coracobrachialis → elbow flexion + forearm supination. Terminates as the lateral cutaneous nerve of the forearm → sensation over the LATERAL forearm.
Worked example
Injury (anterior shoulder dislocation, penetrating arm trauma): weak elbow flexion, absent biceps reflex, numb lateral forearm.
In the exam
Months after an arm injury a man cannot flex his elbow properly; the flexor muscles of the upper arm are wasted and the lateral aspect of his forearm is numb.
What settles it
Musculocutaneous = elbow FLEXION + lateral forearm sensation. Radial = wrist/finger EXTENSION; median = thenar/LOAF + lateral palm; ulnar = intrinsics + medial 1½ digits.
Classically confused with
Radial nerve
Source: TeachMeAnatomy — Musculocutaneous nerve