Clinical and diagnostic variations may occur due to the variable presence of a connection between the median and ulnar nerves in the forearm (Martin-Gruber anastomosis). This incidence has a wide range at 7%-40%. Most commonly, the connection between the nerves is considered to be composed of motor fibers; although, a sensory role has also been described. It is important to note that the number of axons, or the nature of the fibers in this connection, have not yet been elucidated. Fifty upper limbs were examined evaluating morphometric characteristics of the Martin Gruber connection, dissected out, sectioned, and immunohistochemically stained for choline acetyltransferase (ChAT) and analyzed with ImageJ© . The connection was observed in 32% of all cases (16/50). The nerve connections were identified as those in Pattern 1 group (12%-type 1b, 19%-type 1a, and 69%-type 1c) and contained motor (ChAT positive) fibers (40.42 ± 10.5% per connection) with three to four fascicles in each. No statistically significant differences were found according to sex, side, or laterality. There were statistically significant differences in the percentages of ChAT positive fibers; however, this was dependent on the distribution being greater in those not distributed zonally. The presence of this connection is prevalent in almost a third of the cadavers dissected; the understanding of this complex composition in sensory and motor fibers allows for the optimization of diagnosis and treatment of certain median-ulnar nerve injuries. Clin. Anat. 32:501-508, 2019. © 2019 Wiley Periodicals, Inc.
Keywords: choline acetyltransferase; cholinergic fibers; median nerve; nerve fibers; ulnar nerve.
© 2019 Wiley Periodicals, Inc.