A variation in the formation of the brachial plexus characterized by the absence of C8 and T1 fibers in the trunk of the median nerve.

During the dissection of a male cadaver, 80 years old, it was observed that the right median nerve was formed by the junction of two nerve trunks, one originating from the upper and the other from the middle trunk of the brachial plexus (C5, C6 and C7 neurotomes), with subsequent absence of formation of the lateral cord of the plexus. The place of junction lay at 52 mm from the exit of the C6 and C7 nerves from the spine. The musculocutaneous nerve arised from the median nerve after a 38 mm course of the latter. Despite the absence of nerve fibers from the C8 and T1 neurotomes in the trunk of the median nerve, the distribution of its branches was normal.