A prefix brachial plexus with two trunks and one anterior cord

The brachial plexus presents a great variability in formation, division and branching pattern. Its variants are of immense importance during axillary and arm surgery and nerve blockade. The current case highlights a unilateral atypical formation of brachial plexus, the so called prefix, in which the C4 root contributed a large branch to the superior trunk and further anastomosis with the inferior trunk. Thus, the prefix or high brachial plexus consisted of a superior and inferior trunk and one anterior cord. Coexisting neural and arterial variations are also discussed in relation to the data literature. (Folia Morphol 2020; 79, 2: 402–406)