A method for locating the external ramus of the accessory nerve in the posterior cervical triangle

Injury to the external ramus of the accessory nerve during surgery in the posterior triangle of the neck results in a disfiguring and incapacitating paralysis of the trapezius. In order to avoid this, a simple method for locating the ramus was devised. In 17 cadavers the anterior border of the trapezius was palpated and the skin marked at a point 5 cm above its clavicular attachment. A second point, situated over the posterior border of the sternocleidomastoid 6.5 cm below the tip of the mastoid process was similarly marked. A line joining these two points overlies the course of the ramus. As the ramus may lie superficially in this region, the skin incision along this line was followed by blunt dissection of the underlying fascia. The ramus was thus identified at the anterior border of the trapezius 5 cm above its clavicular attachment. This method was successful in all 17 cadavers (34 exposures), even though 3 of these were very obese with short necks. Using this surface marking, injury to the external ramus of the accessory nerve in the posterior triangle can be avoided.