Deep Branch of the Ulnar Nerve, Anterior View

Description

Running distally along the anterior ulnar forearm, the ulnar nerve approaches the wrist adjacent to the ulnar artery, then enters the hand at the level of Guyon canal superficial to the flexor retinaculum. From there, the deep branch of the ulnar nerve sweeps radially across the palm in a clear arch, passing deep to the palmar aponeurosis and flexor tendons to reach the hypothenar compartment, interosseous spaces, and adductor compartment. Nearby intrinsic muscle bellies in the thenar and hypothenar eminences and the slender lumbricals frame its course. Veins and accompanying arterial branches sit more superficial and lateral in the field. Clinically, that arcing deep motor branch is the structure you want in view when teaching why ulnar neuropathy at the wrist can present as isolated intrinsic hand weakness with dorsal ulnar cutaneous sensation spared. Compression in Guyon canal, a ganglion cyst, or repetitive handlebar pressure can affect the deep branch and produce clawing tendencies from interossei and lumbrical denervation, while leaving the ulnar one and a half digits variably intact depending on the level of involvement. For surgeons, this relationship is the map for safe dissection during decompression of Guyon canal and for planning incisions that avoid iatrogenic motor loss. Small branch, big consequence. Hand anatomy labs and peripheral nerve modules will benefit from this anterior dissection-style view when correlating intrinsic muscle actions to their ulnar motor supply and when contrasting cubital tunnel versus ulnar tunnel syndromes. It also supports textbook figures on palmar neurovascular anatomy and operative manuals covering ulnar-sided wrist approaches. Anatomical accuracy verified by SciePro's Medical Advisory Board.