Fetal anatomical variability of the long branches of the brachial plexus

Oleksandr A. Koval; Tatyana V. Khmara

Summary. Information about the anatomical variability of the roots, trunks, bundles, and branches of the brachial plexus is of important practical importance for understanding the mechanisms of injuries to the shoulder, forearm, and hand. Knowledge of the variant anatomy of the brachial plexus in people of different ages is necessary for successful operations, effective analgesia, as well as for the interpretation of clinical symptoms in the practice of neurologists. The aim of the study – to establish the anatomical variability of the musculocutaneous, ulnar, median, and radial nerves in human fetuses of different ages. Materials and Methods. The study was conducted on preparations of the upper limbs of 28 human fetuses of 81.0–310.0 mm parietal-coccygeal length (PCL) using macromicroscopic dissection and morphometry. Results. During anatomical dissection of the upper limbs of 28 human fetuses aged 4–8 months, variants of the fetal topography of bundles and nerves of the subclavian part of the brachial plexus were found in three cases of 170.0 mm, 245.0 mm, 250.0 mm PCL. In fetuses with 170.0 mm and 245.0 mm PCL, connections between the median and ulnar nerves in the form of connecting branches were observed, and the median nerve began with one root from the medial bundle of the subclavian part of the brachial plexus. In a fetus with 250.0 mm PCL, an atypical variant of topography was established for nerves of the lateral and medial bundles of the subclavian part of the brachial plexus, and a doubling of the ulnar nerve was also detected. Conclusions. Double innervation of some shoulder and forearm muscles was found in some human fetuses. The established variants of the topography and connections of the median, ulnar, and musculocutaneous nerves in human fetuses are determined by the peculiarities of the structural organization and multifunctionality of the muscles of the shoulder and forearm, the patterns of their complex prenatal development, the available sources of blood supply, and other factors. The described variants of the fetal anatomy of the long branches of the brachial plexus should be considered not only by theoreticians, but also by clinicians, primarily neurologists, orthopedists, and surgeons

[1] Singh R. Variations of cords of brachial plexus and branching pattern of nerves emanating from them. J Craniofac Surg. 2017;28(2): 543-7. DOI: 10.1097/scs.0000000000003341.

[2] Benes M, Kachlik D, Belbl M, Kunc V, Havlikova S, Whitley A, et al. A meta-analysis on the anatomical variability of the brachial plexus: Part I - Roots, trunks, divisions and cords. Ann Anat. 2021;238: 151751. DOI: 10.1016/j.aanat.2021.151751.

[3] Emamhadi M, Chabok SY, Samini F, Alijani B, Behzadnia H, Firozabadi FA, et al. Anatomical variations of brachial plexus in adult cadavers; A descriptive study. Arch Bone Jt Surg. 2016;4(3): 253-8. DOI: 10.22038/abjs.2016.6491.

[4] Zhang L, Dong Z, Zhang CL, Gu YD. Surgical anatomy of the radial nerve at the elbow and in the forearm: Anatomical basis for intraplexus nerve transfer to reconstruct thumb and finger extension in C7 - T1 brachial plexus palsy. J Reconstr Microsurg. 2016;32(9): 670-4. DOI: 10.1055/s-0036-1584687.

[5] Kirazlı Ö, Tatarlı N, Ceylan D, Hacıoğlu H, Uygun S, Şeker A, et al. A variation of the cords of the brachial plexus on the right and a communication between the musculocutaneous and median nerves on the left upper limb: a unique case. J Neurol Surg A Cent Eur Neurosurg [Internet]. 2013[cited 2022 Sep 02];74(Suppl 1): e176-9. Available from: https://www.thieme-connect.de/products/ejournals/pdf/10.1055/s-0032-1333416.pdf. DOI: 10.1055/s-0032-1333416.

[6] Chrysikos D, Athanasopoulos A, Georgakopoulos P, Antonopoulos I, Samolis A, Troupis T. Anatomical variation of a communicating branch between the musculocutaneous and the median nerve: A Case Report. Acta Med Acad. 2020;49(1): 71-4. DOI: 10.5644/ama2006-124.286.

[7] Dydyk AM, Negrete G, Sarwan G, Cascella M. Median Nerve Injury [Internet]. Treasure Island (FL): StatPearls Publishing; 2022[cited 2022 Aug 31]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK553109/.

[8] Anderson TB, Bordoni B. Anatomy, Shoulder and Upper Limb, Forearm Nerves [Internet]. Treasure Island (FL): StatPearls Publishing; 2022[cited 2022 Aug 31]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK554514/#:~:text=The%20branches%20from%20these%20four,the%20median%20and%20ulnar%20nerves.

[9] Öksüz S, Karagöz H, Külahçı Y, Ülkür E, Uslu A. Long-term follow-up results of a pediatric brachial plexus laceration. Ulus Travma Acil Cerrahi Derg. 2013;19(5): 485-7. DOI: 10.5505/tjtes.2013.07717.

[10] Goubier JN, Teboul F, Papadogeorgou E. Nerve transfers in children with traumatic partial brachial plexus injuries. Microsurgery. 2008;28(2): 117-20. DOI: 10.1002/micr.20461.

[11] Beheiry EE. Anatomical variations of the median nerve distribution and communication in the arm. Folia Morphol (Warsz). 2004;63(3):313-8.

[12] Neto JHS, Neto BC, Eiras ABD, Botelho RHS, Carmo JMM, Passos MARF. The 2-Dimensional and 3-Dimensional Anatomy of the Adult Brachial Plexus Divisions and Cords. Hand (NY). 2022;17(1): 50-4. DOI: 10.1177/1558944720906510.

[13] Da Cunha MR, Dias AAM, de Brito JM, da Silva Cruz C, Silva SK. Anatomical study of the brachial plexus in human fetuses and its relation with neonatal upper limb paralysis. Einstein (Sao Paulo) [Internet]. 2020[cited 2022 Sep 01];18:eAO5051. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6980293/pdf/2317-6385-eins-18-eAO5051.pdf DOI: 10.31744/einstein_journal/2020ao5051.

[14] Tatar I, Kocabiyik N, Gayretli O, Ozan H. The course and branching pattern of the deep branch of the radial nerve in relation to the supinator muscle in fetus elbow. Surg Radiol Anat. 2009;31(8): 591-6. DOI: 10.1007/s00276-009-0487-x.