A cadaveric microanatomical study of the fascicular topography of the brachial plexus

OBJECTIVE: Mapping of the fascicular anatomy of the brachial plexus could provide the nerve surgeon with knowledge of fascicular orientation in spinal nerves of the brachial plexus. This knowledge might improve the surgical outcome of nerve grafting in brachial plexus injuries by anastomosing related fascicles and avoiding possible axonal misrouting. The objective of this study was to map the fascicular topography in the spinal nerves of the brachial plexus. METHODS: The entire right-sided brachial plexus of 25 adult male cadavers was dissected, including all 5 spinal nerves (C5-T1), from approximately 5 mm distal to their exit from the intervertebral foramina, to proximal 1 cm of distal branches. All spinal nerves were tagged on the cranial aspect of their circumference using 10-0 nylon suture for orientation. The fascicular dissection of the C5-T1 spinal nerves was performed under microscopic magnification. The area occupied by different nerve fascicles was then expressed as a percentage of the total cross-sectional area of a spinal nerve. RESULTS: The localization of fascicular groups was fairly consistent in all spinal nerves. Overall, 4% of the plexus supplies the suprascapular nerve, 31% supplies the medial cord (comprising the ulnar nerve and medial root of the median nerve [MN]), 27.2% supplies the lateral cord (comprising the musculocutaneous nerve and lateral root of the MN), and 37.8% supplies the posterior cord (comprising the axillary and radial nerves). CONCLUSIONS: The fascicular dissection and definitive anatomical localization of fascicular groups is feasible in plexal spinal nerves. The knowledge of exact fascicular location might be translatable to the operating room and can be used to anastomose related fascicles in brachial plexus surgery, thereby avoiding the possibility of axonal misrouting and improving the results of plexal reconstruction.