Examination of surgical anatomy of the accessory spinal nerve in neck dissection: Which portion of the dorsal aspect of the sternocleidomastoid muscle is penetrated by the accessory spinal nerve?

Abstract

Recently, preservation of the accessory spinal nerve and the sternocleidomastoid muscle has become common in neck dissection. We observed which portion of the dorsal aspect of the sternocleidomastoid muscle is penetrated first by the accessory spinal nerve during neck dissection (dissections of at least levels 2, 3 and 4 were included in each). A total of 65 neck dissections in 46 cases were enrolled in this examination. The accessory nerve penetrated from the sternal portion in 0 side (0%), the boundary between the sternal portion and the clavicular portion in 4 sides (6.2%), the clavicular portion in 49 sides (75.3%), and the posterior edge of the clavicular portion in 12 sides (18.5%). There were no cases in which the accessory nerve penetrated from the dorsal aspect of the sternal portion first. We conclude that we need not pay attention to the accessory spinal nerve in exfoliation from the dorsal aspect of the sternal portion to the anterior edge of the clavicular portion during neck dissection.