Bicep nerve entrapment

by Nathan Wei, MD, FACP, FACR

Nathan Wei is a board-certified rheumatologist and author of the Second Opinion Arthritis Treatment Kit. It's available exclusively at this website... not available in stores.

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The musculocutaneous nerve is a branch of the lateral cord of brachial plexus which originates from the C5 and C 6 nerve roots. It supplies the biceps, coracobrachialis, and brachialis muscles as well as the skin (lateral cutaneous nerve of forearm).

The most common cause of injury to the musculocutaneous nerve is penetrating injury, but other traumas can also do it. An example would be a dislocation of shoulder.

Compression of the lateral cutaneous nerve of the forearm (LCNF), the distal sensory termination of the musculocutaneous nerve, can occur below the biceps aponeurosis, most commonly after strenuous elbow extension or forearm pronation. Aggressive weight lifting with biceps curls may lead to musculocutaneous nerve palsy that usually affects the dominant side but can be bilateral. Several theories for this condition have been set forth. The most often cited cause is impingement of the musculocutaneous nerve from coracobrachialis muscle hypertrophy. Additionally, a traction mechanism on the nerve from biceps curls as it is anchored by the coracobrachialis muscle has been implicated.

Injury can be overlooked as sensory loss ill-defined and flexion of elbow by brachioradialis may compensate. Feel for flexion of biceps.

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