Objective: The Nerve of Henle (NH) is described as a branch of the ulnar nerve (UN) in the forearm. The objective is to study the existence and anatomic relations of the NH in fresh cadaveric specimens and identify the presence of sympathetic fibers of the ulnar innervation and ulnar artery (UA) in the forearm. Material and Methods: The UN was dissected in 18 fresh cadaveric forearms from the medial epicondyle to the pisiform under 3.5X magnification. The origin of the NH was measured from the medial epicondyle and the pisiform. The NH was identified and dissected in its course with the UA throughout the forearm. The ulnar innervation was divided in 3 segments. The 2 cm nerve samples were obtained from each segment. Additional UA samples were obtained in 3 specimens prior and post the NH reaches the artery, to study its sympathetic innervation. The nerve and artery samples were stained for sympathetic fibers using Tyrosine hydroxylase antibody (ABCAM catalog no. ab62111) and anti-rabbit Ig-HRP (Life Technologies, catalog no. 65-6120). Fascicles area of the nerve samples were measured using Motic Images Plus. The number of sympathetic fibers per fascicle studied was quantified in 5 specimens. Results: The NH was present in 100% of the specimens. In all, 83% had a typical presentation (McCabe and Kleinert). In the typical presentation, the NH divided proximally in the forearm from UN on average 10.23 cm distal to the medial epicondyle and 15.4 cm proximal to the pisiform. In the atypical presentation (17% of the specimens), the NH divided on average 17.9 cm distal to the medial epicondyle and 8.76 cm proximal to the pisiform. The dorsal sensory branch divided from the UN on average 7.91 cm proximal to the pisiform. Sympathetic nerve fibers were found in all the fascicles studied of the nerve samples. However, when analyzing the area of the fascicles studied, the NH had a higher number of sympathetic fibers per square millimeter compared with the UN and dorsal sensory nerve. The UA appear to present more sympathetic fibers between the media and adventitia after the NH reaches the artery. Conclusion: The NH was observed in all the forearms studied (100%). Previous studies described the presence of NH up to 58% of the specimens. We think that the main difference in the presence of NH is because we only used fresh cadaveric forearms. A proximal origin of the NH was the most common presentation. In all the cases, the NH joined the UA in the forearm after exiting the UN, showing a strong anatomic relation between these 2 structures. Immunochemistry confirmed the presence of sympathetic fibers in all the nerves of the ulnar innervation. If we consider the area of the fascicles studied, the greatest carrier of sympathetic fibers per square millimeter in the ulnar innervation was the NH. It appears that the UA presents more sympathetic fibers between the media and adventitia after the NH reaches the artery. There might be a place for NH resection in the treatment of vasospastic disorders.
