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.

Anatomical variations of brachial plexus in fetal cadavers

“…The study by Nayak et al described a superior trunk variation that had been formed by the C5, C6 and C7 nerve roots (17). Different authors also found this variation (2,13). Furthermore, the study by Aragão et al reported that there was a formation of four trunks in 2.5% of the cases (2).…”

The brachial plexus – explaining its morphology and variability by a generic developmental model

“…10C,D Bilateral absence of lower trunk Fig. 1 in Aragao et al (2014) This concerns very distal mergers of the C8a and T1a sclerotome axon bundles, which run independently and only merge at the point of formation of the median nerve.…”

“…However, within this standard view, the plexus remains a structure of enigmatic complexity, which students generally learn by rote and thereafter readily forget. Yet, the surgeon will find its variability far greater than the textbooks suggest, as reflected by the documented complexity of plexus reconstruction (Kerr, ; Don Griot et al ; Das & Paul, ; Prakash et al ; Singhal et al ; Vilamere et al ; Aggarwal et al , , ; Yildiz et al ; Adam et al ; Muthoka et al ; Chaudhary et al ; Chaware et al ; Wozniak et al ; Van de Velde et al , ; Aragao et al ; Bhosale & Havaldar, ; Govindarajan et al ; Mian et al ; Claassen et al ; Emamhadi et al ; Leonhard et al ; Padur et al ; Tubbs et al ).…”

Variant Anatomy of the Brachial Plexus

“…Описаны случаи, когда спинальные нервы С5 и С6 не объединяются в первичный верхний ствол [2], а С8, Th1 -в первичный нижний ствол [2,7]. Singla RK et al (2013) обнаружили в своём исследовании сплетение, в составе которого было 2 ствола [8].…”

“…Cases have been described when the C5 and C6 spinal nerves do not merge to form the primary upper trunk [2], while C8 and Th1 do not merge to form the primary lower trunk [2,7]. Singla RK et al (2013) in their study found a plexus, which included two trunks [8].…”