High trifurcation of the ulnar nerve with the volar sensory branch entering the hand superficial and radial to the Guyon’s canal: A case report

INTRODUCTION: Trifurcation of the ulnar nerve proximal to the Guyon’s canal is rare. In these cases, the main trunk of the nerve divides few cm proximal to the canal into 3 branches: a deep motor branch and two superficial volar sensory branches (the common digital nerve of the 4th web and the ulnar digital nerve of the little finger). All 3 branches then enter the Guyon’s canal. PRESENTATION OF A CASE: We report on a rare case of high trifurcation of the ulnar nerve in the mid-forearm. The ulnar nerve divided into 3 branches: an ulnar dorsal sensory branch, an intermediate motor branch, and a radial volar sensory branch. The dorsal sensory branch entered the dorsal aspect of the forearm. The motor branch entered the Guyon’s canal. The radial volar sensory branch did not enter the Guyon’s canal, coursing superficial and radial to the canal to enter the hand. DISCUSSION: The clinical implications of this very rare branching pattern of ulnar nerve are discussed along with a review of previously reported branching patterns of the nerve in the forearm. CONCLUSION: Our case of high trifurcation of the ulnar nerve is unusual with no similar cases in the literature. This branching pattern is associated with an abnormal course of the volar sensory branch; marking it relevant in clinical practice.