A brachial plexus variation characterized by the absence of the superior trunk

During routine dissection of a 55-year-old female cadaver, a variation of the brachial plexus characterizedby the absence of the superior trunk on the left side was observed. The ventral rami of the C5 and C6 nerveroots, without joining to form the superior trunk, independently divided into anterior and posterior divisions,which joined the lateral and posterior cords, respectively. Additionally, the suprascapular nerve that normallyoriginates from the superior trunk initiated exclusively from the C5 nerve root in this variation. Similarvariations in the brachial plexus were not observed on the contralateral side. The details of this variation and itsclinical significance are discussed herein.