Focal atrophy of the multifidus muscle in lumbosacral radiculopathy.

A patient with compelling clinical and electrodiagnostic evidence of a right L5 radiculopathy had focal atrophy of the multifidus at the appropriate level, which served to confirm the radicular nature of the process. The multifidus muscles are innervated by a single root, in contrast to the polysegmental innervation of the rest of the paraspinal muscle mass. Imaging studies may complement needle electromyography in the evaluation of this important structure.