Accessory nerve damages and impaired shoulder movements after neck dissections

After neck dissection, where the accessory nerve is often excised patients usually complain of impaired shoulder movements. The accessory nerve forms a plexus with branches of the cervical nerves C2, C3, and C4. In the present study, the accessory nerve was examined during neck dissections to clarify the incidence of motor fibers in joining branches, and the function of the motor fibers was evaluated postoperatively in relation to shoulder movements.

Presence of cervical contributions to the accessory nerve were examined in 20 neck sides in 15 patients. Postoperative function of the shoulder movements was evaluated by manual muscle testing (MMT) and electromyography (EMG).

Motor fibers in cervical contributions were noted on four sides (20%) by stimulation of joining branches. When the accessory nerve was excised, scapular elevation was rarely impaired even if there were no motor fibers in the cervical contributions. Excision of the accessory nerve caused poor scapular adduction and impaired scapular depression and adduction in most cases even if motor fibers in the cervical contributions existed.

Postoperative impairment of scapular movements was not attributed to the presence or absence of motor fibers in joining branches. Results obtained with electromyography did not represent the practical function of the muscle.