The zygomaticus major is the most important smile muscle, drawing the corner of the mouth superolaterally to produce the zygomatic smile. In facial palsy reconstruction, restoring zygomaticus major function is the primary goal. Gracilis free muscle transfer reinnervated by the masseteric nerve (bite-activated smile) or cross-face nerve graft (spontaneous smile) replaces the zygomaticus major function.
| Origin | Zygomatic bone (lateral surface, anterior to the zygomaticomaxillary suture) |
|---|---|
| Insertion | Modiolus and upper lip (blending with orbicularis oris and levator labii fibres) |
| Nerve Supply | Zygomatic and buccal branches of the facial nerve (VII) |
| Blood Supply | Facial artery perforators |
| Actions | The primary smile muscle — draws the upper lip superolaterally to produce a smile; The most important muscle for facial expression and emotional communication |
|---|
The dimple of the cheek is caused by a bifurcation of the zygomaticus major — the skin between the two slips is tethered to the underlying fascia, producing the dimple during smiling. Dimpleplasty creates this tethering artificially. In Bell's palsy, the zygomaticus major is the muscle most obviously impaired — smile asymmetry is the most visible sign and the primary outcome measure in treatment.
The zygomaticus major is palpable as the diagonal muscle band from the zygomatic arch to the oral commissure, becoming prominent during genuine smiling.
Zygomaticus major paralysis producing smile asymmetry in facial nerve palsy managed with corticosteroids acutely and facial reanimation surgery for persistent palsy.
