The palmaris brevis is the only intrinsic muscle inserting into palm skin, cupping the hypothenar eminence during grip. It is the first muscle supplied by the superficial ulnar nerve after Guyon canal — its testing (ability to wrinkle hypothenar skin) distinguishes distal ulnar nerve lesions. In Guyon canal decompression, the palmaris brevis forms a superficial landmark.
| Origin | Medial flexor retinaculum and palmar aponeurosis |
|---|---|
| Insertion | Skin of the hypothenar eminence — the only muscle inserting into the skin of the palm |
| Nerve Supply | Superficial branch of the ulnar nerve (C8, T1) — the first muscle innervated by the ulnar nerve distal to the wrist |
| Blood Supply | Ulnar artery |
| Actions | Wrinkles the skin of the hypothenar eminence — cups the medial palm for grip; Protects the ulnar nerve and artery at Guyon canal by tensioning the overlying skin |
|---|
Palmaris brevis spasm syndrome produces visible hypothenar skin wrinkling associated with ulnar nerve pathology. Paradoxically, preserved palmaris brevis (superficial ulnar branch) with absent hypothenar muscle activity (deep ulnar branch) localises the Guyon canal lesion to the deep branch distal to the palmaris brevis supply point.
Palmaris brevis wrinkling of the hypothenar skin during a firm grip is its clinical assessment — its contraction is visible as hypothenar skin corrugation.
Preserved palmaris brevis (superficial branch) with deep branch weakness localises Guyon canal compression distal to the superficial branch takeoff.
