Shoulder Mobility after Neck Dissection.

The “so-called shoulder syndrome” occurs frequently after neck dissection. However, some patients whose accessory nerves were sacrificed during operation have normal shoulder mobility. There is some controversy about whether the cervical nerves to the accessory nerve innervate the trapezius muscle.Using a neurostimulator, we examined the motor innervation of the cervical contributions during operation. After neck dissection, we examined the function of the trapezius muscle with manual muscle testing (MMT) and electromyography (EMG) and correlated the results with whether or not the accessory nerve had been preserved.In eight of 42 sides (19%) motor fibers from the cervical nerves reached the trapezius muscle. Scapular elevation was not greatly restricted even if the accessory nerve had been sacrificed, presumably because of the compensatory function of the levator scapulae muscle. Motor action potentials of the inferior fibers of four trapezius muscles were present even after the accessory nerve on that side had been sacrificed. It appears, therefore, that the inferior fibers of the trapezius muscle can be innervated by nerves other than the accessory nerve.