Which nerve injury classically presents with weakened elbow flexion and sensory loss over the lateral forearm?

Which nerve injury classically presents with weakened elbow flexion and sensory loss over the lateral forearm?

• A. Radial nerve injury
• B. Ulnar nerve injury
• C. Musculocutaneous nerve injury
• D. Median nerve injury

Answer: (C)

Elbow flexion is mainly carried out by the biceps brachii and brachialis, both of which are innervated by the musculocutaneous nerve. This nerve also provides sensation to the lateral forearm via the lateral antebrachial cutaneous branch. When the musculocutaneous nerve is injured, you see weakened elbow flexion and loss of sensation over the lateral forearm. The other nerves don’t produce that exact pattern: radial nerve injuries limit elbow extension and affect the dorsolateral forearm/hand sensation; median nerve injuries affect most forearm flexors and the lateral palm/fingers; ulnar nerve injuries affect the intrinsic hand muscles and the medial hand. So the combination of reduced elbow flexion with lateral forearm sensory loss points to a musculocutaneous nerve injury.

Elbow flexion is mainly carried out by the biceps brachii and brachialis, both of which are innervated by the musculocutaneous nerve. This nerve also provides sensation to the lateral forearm via the lateral antebrachial cutaneous branch. When the musculocutaneous nerve is injured, you see weakened elbow flexion and loss of sensation over the lateral forearm. The other nerves don’t produce that exact pattern: radial nerve injuries limit elbow extension and affect the dorsolateral forearm/hand sensation; median nerve injuries affect most forearm flexors and the lateral palm/fingers; ulnar nerve injuries affect the intrinsic hand muscles and the medial hand. So the combination of reduced elbow flexion with lateral forearm sensory loss points to a musculocutaneous nerve injury.