The long thoracic nerve: Its origin, branches, and relationship to the middle scalene muscle.

Anatomical knowledge regarding the long thoracic nerve (LTN) is important during surgical procedures considering that dysfunction of this nerve results in clinical problems. The purpose of this study was to explore the anatomy of the LTN, its origin, configuration, branching pattern, and relationship to the middle scalene muscle (MSM). The course of the LTN was investigated in 12 embalmed cadavers (21 sides). We defined four different types for this nerve according to the origins of its roots. The most common formation of the LTN was the contribution of three branches that originated from the fifth, sixth, and seventh cervical ventral roots. C5 and C6 components or upper portion of the LTN roots lay primarily between the middle and posterior scalene muscles, sometimes passed through the MSM, and less frequently coursed over the MSM. C7 contributions to the LTN were always located anterior to the MSM. Contributions from C8 were also found over the MSM. The median number of branches arising directly from the cervical roots and branches arising from the main trunk of the nerve were 3 and 7, respectively. Along its course, the median number of branches to the serratus anterior was 10.