The frontalis is the forehead muscle, the only elevator of the eyebrow, running from the galea aponeurotica to the eyebrow skin without any bony attachment. Its contraction produces the horizontal forehead lines characteristic of sustained eyebrow elevation during concentration, surprise, or to compensate for ptosis of the upper eyelid. It has no bony origin or insertion — its entire force is transmitted through the galea above and the eyebrow skin below.
| Origin | Galea aponeurotica at the coronal level |
|---|---|
| Insertion | Skin of the eyebrow and forehead, blending with the procerus, corrugator, and orbicularis oculi |
| Nerve Supply | Temporal branch of the facial nerve (CN VII) |
| Blood Supply | Supraorbital and supratrochlear arteries |
| Actions | Elevation of the eyebrows; Wrinkling of the forehead skin horizontally |
|---|
When the levator palpebrae superioris is weak or paralysed (ptosis), the frontalis compensates by elevating the brow to mechanically lift the upper eyelid, producing the characteristic forehead wrinkling of patients with chronic ptosis as they strain to see clearly.
The frontalis is the primary target of botulinum toxin injection for forehead wrinkle treatment, the most commonly performed aesthetic procedure worldwide. Over-treatment produces complete frontalis paralysis, eyebrow ptosis, and a heavy brow appearance. In upper motor neurone facial palsy (stroke), the frontalis is partially spared because the forehead muscles receive bilateral cortical representation, preserving some brow elevation despite loss of lower facial movement — a clinically useful sign distinguishing central from peripheral facial palsy.
The frontalis is palpable as the horizontal muscle of the forehead overlying the frontal bone, becoming firm during eyebrow elevation. Its separation from the underlying bone by loose areolar tissue allows the forehead to be elevated and dissected in the subgaleal plane during forehead lift surgery.
Inability to elevate the eyebrow from temporal branch facial nerve injury during forehead surgery, producing brow ptosis that may require corrective browpexy.
