Electrically silent muscle visible by ultrasound.

A 65-year-old woman with multiple chronic cranial neuropathies had spinal accessory innervated muscles that were virtually invisible to electromyography. Ultrasound imaging revealed the extensive atrophy and increased echogenicity that corresponded to the thinness of the muscles and their loss of insertional activity. In patients with severe atrophy of trapezius or sternocleidomastoid muscles, ultrasound may help in identify chronically denervated muscle.