[The spinal accessory nerve (n. accessorius) I: anatomical study].

INTRODUCTION: In order to increase knowledge of the spinal accessory nerve concerning its situation, trajectory and terminal branches and also the connections with the cervical plexus, the authors report an anatomical study based on 11 dissections of the trapezius muscle mode of innervation and the connections between the accessory nerve, the sternocleidomastoid and trapezius muscles. DISCUSSION: The accessory nerve is a muscular nerve and supplies the main innervation to the trapezius muscle especially for the superior and middle sections. There is a clear participation of the cervical plexus either through the trapezius muscle by nerve anastomosis behind the trapezius or directly especially in the distal portion. CONCLUSION: This anatomical study allows a better understanding of the clinical aspects and the indications of nerve repairs.