title: Anatomical study of accessory nerve innervation relating to functional neck dissection.
abstract: OBJECTIVE
  The present study sought to clarify correlations of accessory nerve innervation in the neck region and innervation of the sternocleidomastoid and trapezius muscles with postoperative dysfunction after functional neck dissection by macroscopic observation.
  
  
  METHODS
  The materials used in this study were 35 cadavers provided for anatomical practice to the Department of Anatomy, Tokyo Dental College. The accessory nerve was identified at the anterior margin of the trapezius muscle, and its innervation in the posterior triangle of the neck was examined in detail.
  
  
  RESULTS
  The superficial cervical vein vascularizes the anterior margin of the trapezius muscle near an area where the main trunk of the accessory nerve innervates the trapezius muscle. The results showed 3 types of accessory nerve innervation of the sternocleidomastoid muscle: Type A, the not penetrating type; Type B, the partially penetrating type; and Type C, the completely penetrating type. In addition, 5 types of innervation of the trapezius muscle by the main trunk and branches of the accessory nerve were apparent, with the number of branches innervating the muscle ranging from 0 to 4.
  
  
  CONCLUSIONS
  Dysfunction after functional neck dissection can thus be avoided by paying attention to not only the main trunk of the accessory nerve, but also the branches. Moreover, when identifying accessory nerve innervation of the trapezius muscle, the superficial cervical vein may offer a useful surgical landmark.
authors.affiliation: Department of Anatomy, Tokyo Dental College, Chiba, Japan. shiozaki@tdc.ac.jp
authors.forename: Kazunari
authors.initials: K
authors.lastname: Shiozaki
authors.forename: Shinichi
authors.initials: S
authors.lastname: Abe
authors.forename: Hiroko
authors.initials: H
authors.lastname: Agematsu
authors.forename: Satoshi
authors.initials: S
authors.lastname: Mitarashi
authors.forename: Koji
authors.initials: K
authors.lastname: Sakiyama
authors.forename: Masatsugu
authors.initials: M
authors.lastname: Hashimoto
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Ide
mesh_terms: D000055:Accessory Nerve / Q000033:anatomy & histology*; D002102:Cadaver; D006801:Humans; D018482:Muscle, Skeletal / Q000294:innervation; D009333:Neck / Q000098:blood supply / Q000294:innervation*; D037981:Neck Dissection; D009334:Neck Muscles / Q000098:blood supply / Q000294:innervation; D012782:Shoulder / Q000294:innervation; D014680:Veins / Q000033:anatomy & histology