A two trunked brachial plexus: a case report.

The brachial plexus is a major and a complicated plexus at the root of the neck. It is formed by the ventral primary rami of the C5, C6, C7, C8 and the T1 spinal nerves. During the routine under graduate dissection of the right upper limb of an adult female cadaver, a variant pattern of a two trunked brachial plexus was encountered. The upper trunk was formed by the fusion of the C5 and the C6 roots. The C7 root, instead of continuing as the middle trunk, joined with the roots of C8 and T1 to form the lower trunk. On the left side, the usual pattern of the brachial plexus was seen. The knowledge on such variations are of interest to anatomists, clinicians, anesthesiologists and especially, to surgeons. These are of immense importance during surgical explorations of the axilla and the arm region and also during nerve blocks. It also helps the clinicians in getting a proper understanding of some previously unexplained clinical symptoms. Further, the ontogeny and the phylogeny of this entity have been discussed in detail.