Anatomical variations of the median nerve in axilla and arm in fetuses from Córdoba, Argentina

Abstract

The median nerve, is a mixed nerve, terminal branch of the brachial plexus, which contains fibers from the five roots that make up this plexus (C5, C6, C7, C8 y T1),  a fact that determine its importance, in addition to its territory of innervation. The aim is to investigate the anatomical varieties in the formation of median nerve and its abnormal communication with other terminal branches of the brachial plexus.  Also, determine the bilaterally of these, their incidence according to sex and highlight their clinical importance.

30 axillary and anterior regions of arms corresponding to 15 fetuses were dissected, from the Hospital Misericordia and the Maternidad Provincial of the City of Córdoba, up to 500 g, from 16 to 24 weeks of gestation, fixed in 5% formaldehyde. The specimens were placed in a supine position and the area was accessed through an anterior approach using microdissection techniques and instruments. Subsequently, the results were tabulated for correct interpretation and analysis.

4 types of varieties were found: IIb (3 roots, the extra root comes from the musculocutaneous nerve); IIe (3 roots, the extra root comes from the anterior branch of the middle trunk); VI (communicating branch with musculocutaneous nerve) and VIIe (the anterior branch of the middle trunk forms the lateral root of the median nerve). 25 regions were unremarkable (83,33%) and 5 with varieties (16,67%).  Type IIb and VI variations occurred in 2 plexuses and type IIe and VIIe only in one. Moreover, in the same plexus, type IIb and VIIe variations were presented.

In conclusion, the anatomical variations described are present in a 16,67% of the regions explored. Of these cases, 3 were unilateral and 1 was bilateral asymmetric. In addition, 80% of the varieties occurred in male fetuses and 20% in femenine. Given that the existence of research projects on this topic, particularly in fetuses, is scarce, this article allows us to generate a record with the purpose of preventing diagnostic errors due to atypical symptoms and iatrogenic lesions due to confusion in surgical procedures and anesthesia.