Isolated Brachialis Muscle Atrophy
Isolated brachialis muscle atrophy, a rare entity with few reported cases in the literature, is explained by a variety of etiologies. We present a case of unilateral, isolated brachialis muscle atrophy that likely resulted from neuralgic amyotrophy.
Others have similarly described isolated wasting of 1 muscle with the sparing of other muscles with a common innervation. Isolated atrophy of the extensor or flexor pollicis longus has been reported as variants of either posterior or anterior interosseous neuropathy, respectively.7,8 Nerve fibers in the brachial plexus destined to innervate muscles supplied by the anterior interosseous nerve may be the cause of the motor deficit in cases of anterior interosseous nerve palsy, which seem to be associated with brachial plexitis.9
We present a case of isolated brachialis muscle atrophy after a minor trauma that may have resulted from Parsonage-Turner syndrome or a variant of brachial plexitis. The constellation of shoulder and arm pain, with subsequent muscle atrophy, makes this diagnosis likely.
