A Case of Multiple Simultaneous Brachial Plexus Anomalies in One Specimen

INTRODUCTION. In a typical brachial plexus, upper, middle, and lower trunks subdivide into anterior and posterior divisions reflecting flexor and extensor compartment innervation, respectively. Posterior divisions combine to form the posterior cord, anterior divisions combine to form medial and lateral cords, which give rise to terminal branches. In the present case, several reported and unreported variations were found within the same plexus of one cadaver. These configurations which have not been reported together in previous studies are clinically significant. RESOURCES. The variations of the brachial plexus were found during routine dissection of a 77-year-old female cadaver at PCOM GA Anatomy lab. Typical dissection techniques were utilized to expose the brachial plexus. DESCRIPTION. The following variations were found: 1) Posterior division coming from C8, instead of typical position from lower trunk. 2) Axillary nerve arising from posterior division of upper trunk without contributions from C7, C8, T1. 3) Contribution from C7 abnormally piercing pectoralis major. 4) Medial pectoral nerve absent. 5) Anterior division of middle trunk contributing to lateral cord absent. 6) Absent contribution from C7 to musculocutaneous nerve. 7) Anterior division of middle trunk directly contributing to lateral contribution of median nerve. 8) Posterior division of upper trunk contributing to posterior cord distal to emergence of thoracodorsal nerve. 9) Long thoracic nerve is missing a contribution from C7. SIGNIFICANCE. Although variations have been well documented, there have been few discoveries of multiple variations occurring in one extremity. Clinically, the present case would have exhibited atypical myotome and dermatome patterns on assessment. Knowledge of these variations of the brachial plexus are clinically crucial not only to physical therapists but to other medical professionals, especially in cases of thoracic outlet syndrome and brachial plexus nerve blocks.