Accessory nerve injury during carotid endarterectomy

Injury to the accessory nerve (cranial nerve XI) during carotid endarterectomy is rare; to date only three cases have been reported in the literature. Traction on the sternocleido-mastoid muscle was the proposed mechanism of injury in all three cases. Four cases of accessory nerve palsy occurred in 850 carotid endarterectomies performed between 1978 and 1986 at this institution, an incidence of 0.47%. All four patients had classic signs and symptoms of accessory nerve injury, which developed between 20 and 60 days after operation. The three most recent cases were examined specifically for accessory nerve injury in the immediate postoperative period and exhibited normal trapezius function. None had any other central nervous system dysfunction. Two of these patients regained full accessory nerve function and the most recent case is showing signs of reinnervation with conservative therapy. Isolated central nervous system and spontaneous accessory nerve palsies are exceptionally rare, and since any traction injury or transection should have been detected by postoperative examinations in three of four patients, we propose surgical scar formation as a mechanism of accessory nerve palsy after carotid endarterectomy. If such a palsy develops in the postoperative period, we recommend conservative therapy.