Anastomosis between both hypoglossal nerves in a 30 mm human embryo.

In this paper we present the first description of an anastomosis between both hypoglossal nerves during the embryonic period, a very uncommon anatomical variation. This was observed in a 30 mm crown-rump (C-R) length human embryo (Carnegie stage 23) from the Bellaterra Collection (Prof. Doménech Mateu), stained for nerve fibers. The anastomosis consisted of a large diameter trunk (36.7 microns) situated in front of and slightly below the hyoid cartilage, and clearly distinguishable from the anastomosis found in adults, which has a very fine diameter and is located in the suprahyoid region.