Variations of the origin of collateral branches emerging from the posterior aspect of the brachial plexus.

Background: The frequency of variation found in the arrangement and distribution of the branches in the brachial plexus, make this anatomical region extremely complicated. The medical concerns involved with these variations include anesthetic blocks, surgical approaches, interpreting tumor or traumatic nervous compressions having unexplained clinical symptoms (sensory loss, pain, wakefulness and paresis), and the possibility of these structures becoming compromised. The clinical importance of these variations is discussed in the light of their differential origins.

Methods: The anatomy of brachial plexus structures from 46 male and 11 female cadaverous specimens were studied. The 40-80 year-old specimens were obtained from the Universidad Industrial de Santander's Medical Faculty's Anatomy Department (dissection laboratory). Parametric measures were used for calculating results.

Results: Almost half (47.1%) of the evaluated plexuses had collateral variations. Subscapular nerves were the most varied structure, including the presence of a novel accessory nerve. Long thoracic nerve variations were present, as were the absence of C5 or C7 involvement, and late C7 union with C5-C6.

Conclusion: Further studies are needed to confirm the existence of these variations in a larger sample of cadaver specimens.