Anatomical study of accessory nerve innervation relating to functional neck dissection.
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.
Shiozaki
Kazunari
K
Department of Anatomy, Tokyo Dental College, Chiba, Japan. shiozaki@tdc.ac.jp
Abe
Shinichi
S
Agematsu
Hiroko
H
Mitarashi
Satoshi
S
Sakiyama
Koji
K
Hashimoto
Masatsugu
M
Ide
Yoshinobu
Y
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