Occurrence, duration and prognosis of unexpected accessory nerve paresis in radical neck dissection.

Injuries to the spinal accessory nerve in connection with radical neck dissection occur frequently, despite the preservation of the nerve. Although the surgeon was unaware of any serious lesion of the accessory nerve, a trapezius paresis of varying degree was observed in about 60% of the patients during convalescence. The shoulder function improved in most patients, but major paresis with loss of essential rotary and supportive functions of the trapezius muscle persisted in 17% of the patients operated on. No further improvement was seen 18 months after the surgical trauma.