The palmaris brevis is a small, thin subcutaneous muscle at the medial palm that inserts directly into the overlying skin rather than bone, making it one of the rare cutaneous muscles in the hand. Its contraction wrinkles the hypothenar skin and deepens the palmar cup, marginally improving grip. Its superficial position over the ulnar nerve and artery at Guyon canal means that its wasting or denervation is a clinical sign of superficial ulnar nerve involvement.
| Origin | Flexor retinaculum and palmar aponeurosis |
|---|---|
| Insertion | Skin of the medial palm (hypothenar skin) |
| Nerve Supply | Superficial branch of the ulnar nerve (C8, T1) |
| Blood Supply | Ulnar artery |
| Actions | Wrinkles the skin of the hypothenar eminence; Deepens the cup of the palm to improve grip; Protects the ulnar neurovascular bundle in Guyon canal |
|---|
By wrinkling the medial palm it deepens the cup shape that improves gripping and catching, and its contraction is a visible sign of intact superficial ulnar nerve function at the wrist level.
Palmaris brevis contraction visible as skin wrinkling over the hypothenar eminence indicates an intact superficial branch of the ulnar nerve distal to Guyon canal. Its absence or asymmetry on attempted contraction localises an ulnar nerve lesion to a specific level. The muscle overlies the ulnar nerve and artery as they exit Guyon canal, giving it protective mechanical significance for these structures.
The palmaris brevis is visible as a skin wrinkling over the hypothenar eminence during forceful grip or direct stimulation of the hypothenar skin, but is not individually palpable as a distinct muscle belly.
Loss of visible hypothenar skin wrinkling indicating superficial ulnar nerve injury at or distal to Guyon canal, useful in localising the level of ulnar nerve pathology.
