Variations in the formation of the trunks of brachial plexus

Abstract Background: The brachial plexus is a complex network of nerves that innervates the upper limbs. Variations in brachial plexus are common, as well as its relationships with other anatomical structures, gaining thus clinical and surgical importance. The aim of this study was to report variations in the formation of the trunks of brachial plexus. Material and Methods: Forty upper limbs from 20 human fetuses were used, fixed and kept in 10% formol solution. Fetal age was estimated from the hallux-calcaneus length and ranged from 20 to 37 weeks of gestation, with a mean of25.63 weeks. The plexus were dissected without the aid of optical instruments, and the access route for dissection began 2 cm below the mastoid process, followed the posterior border of the sternocleidomastoid muscle until the medial third of the clavicle, and then went through the deltopectoral groove until the arm. Results: Of the 40 plexuses investigated, 37 (92.5%) had the usual trunk formation, and 3 (7.5%) showed variation in its formation. Among these, in 2 (5%) plexuses of a single fetus, the upper trunk was formed by the C5, C6 and C7 roots, the middle trunk by the C8 root, and the lower trunk by the T1 root, both on left and right sides. In 1 (2.5%) plexus of another fetus, there was the formation of four trunks on the left side: the first trunk was formed by the C4 and C5 roots, the second by the C7 root, the third by the C8 root, and the forth by the T1 root. Conclusion: Studies on variations in brachial plexus should continue to draw the attention of different healthcare professionals who work directly or indirectly with this plexus in their daily routine.