title: Patterns of connections between the musculocutaneous and median nerves in the axilla and arm.
abstract: Variations in connections between the musculocutaneous and median nerves in the arm are not as uncommon as was once thought. This opinion led us to perform a study in 138 cadavers (66 male, 72 female). These variations were seen in 64 cadavers (46.4%), 9 bilaterally and 55 unilaterally (26 right and 29 left); in total, therefore, variations were observed in 73 out of 276 arms (26.4%), 42 male and 31 female. No statistically significant differences by gender and side were observed. We classify the variations in three main patterns: Pattern 1, fusion of both nerves (14 arms, 19.2%); Pattern 2, presence of one supplementary branch between both nerves (53 arms, 72.6%); and Pattern 3, two branches (5 arms, 6.8%). Pattern 2 was further subdivided into a sub-group 2a when a single root from the musculocutaneous nerve contributed to the connection (51 arms, 69.9%), and 2b when there were two roots from the musculocutaneous nerve (2 arms, 2.7%). A combination of Patterns 1 and 2a was observed in one case (1.4%). Further variations are described, published classification systems are reviewed and a meta-analysis of previous results is presented. An overall incidence of 33% of variant arms was observed. Of these variant arms, Pattern 1 represented 13.1%, Pattern 2 represented 75.4%, and Pattern 3, 8.5%, similar to our figures.
authors.affiliation: Department of Anatomy, University of Cambridge, Cambridge, United Kingdom.
authors.forename: David
authors.initials: D
authors.lastname: Choi
authors.forename: Marc
authors.initials: M
authors.lastname: Rodríguez-Niedenführ
authors.forename: Teresa
authors.initials: T
authors.lastname: Vázquez
authors.forename: Ian
authors.initials: I
authors.lastname: Parkin
authors.forename: José R
authors.initials: JR
authors.lastname: Sañudo
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001132:Arm / Q000033:anatomy & histology / Q000294:innervation; D001365:Axilla / Q000033:anatomy & histology / Q000294:innervation; D001917:Brachial Plexus / Q000033:anatomy & histology*; D002102:Cadaver; D005260:Female; D006801:Humans; D008297:Male; D008475:Median Nerve / Q000033:anatomy & histology*; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000294:innervation*; D009138:Musculocutaneous Nerve / Q000033:anatomy & histology*; D012737:Sex Factors