occipitofrontalis

The occipitofrontalis, also known as the epicranius, is a paired muscle of the scalp that covers the skull. It consists of two vertically arranged muscle bellies, the frontal belly (frontalis) and the occipital belly (occipitalis), which are connected by the galea aponeurotica.

The frontal belly originates from the galea aponeurotica and inserts into the skin of the eyebrows and the forehead. The occipital belly originates from the superior nuchal line and adjacent occipital bone and inserts into the galea aponeurotica. The galea aponeurotica acts as a common intermediary tendon between the two bellies, allowing coordinated movement of the scalp and brow region.

Innervation of the occipitofrontalis is via the facial nerve (cranial nerve VII). The frontalis portion is typically supplied by the temporal branches of the facial nerve, while the occipitalis portion is supplied by the posterior auricular branch. Blood supply comes from branches of the external carotid system, notably the superficial temporal artery and the posterior auricular artery, with contributions from the occipital artery.

Functionally, the frontal belly elevates the eyebrows and the skin of the forehead, producing horizontal wrinkles. The occipital belly retracts or moves the scalp backward. Together, the two parts enable a range of facial expressions and scalp movements, and they play a role in expressions of surprise or curiosity.

Clinical relevance includes potential weakness or paralysis from facial nerve injury, which can impair forehead movement and eyebrow elevation. Surgical procedures or trauma to the scalp may affect its function, and the muscle is sometimes targeted in cosmetic procedures to alter brow position.