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Superficial Branch of the Ulnar Nerve

ramus superficialis nervi ulnaris

The superficial branch of the ulnar nerve is the purely sensory terminal division of the ulnar nerve in Guyon's canal, arising at the pisiform level and dividing into the proper palmar digital nerve to the little finger and the common palmar digital nerve to the ring-little web space. It supplies the palmar skin of the little finger, the ulnar half of the ring finger, and the hypothenar skin. It is the sensory branch tested in ulnar nerve assessment.

Region: Hand & Wrist

Clinical Relevance

Clinical Notes

Guyon's canal compression at Zone 2 (between the pisiform and hamate hook) affects the deep motor branch while sparing the superficial sensory branch — producing pure motor ulnar palsy (intrinsic hand weakness without sensory loss). Zone 1 compression (proximal to the bifurcation at the pisiform) affects both branches producing combined motor and sensory loss. Zone 3 compression (distal to the bifurcation) affects the superficial branch alone producing sensory loss without intrinsic weakness. Clinical localisation using this zone system guides surgical decompression of the appropriate branch within Guyon's canal.

Pathology

Common Injuries & Conditions

Superficial Ulnar Branch Compression in Guyon's Zone 3

Pressure from cycling gloves or handlebar grip over the hypothenar eminence compresses the superficial branch of the ulnar nerve in Guyon's Zone 3 distal to the deep branch bifurcation, producing sensory loss in the ring and little fingers without intrinsic muscle weakness; rest from cycling and padded gloves resolve the neuropraxia.