Epicranius

Epicranius, also known as the occipitofrontalis, is a broad, bipartite muscle of the scalp that covers the skull from the forehead to the back of the neck. It consists of two parts, the frontalis (frontal belly) and the occipitalis (occipital belly), connected across the galea aponeurotica.

Anatomy and attachments: The frontal belly originates from the galea aponeurotica and inserts into the skin of the eyebrows and forehead, enabling movement of the forehead skin. The occipital belly originates from the superior nuchal line of the occipital bone (and the mastoid part of the temporal bone) and inserts into the galea aponeurotica. The two parts thus function together to move the scalp.

Innervation and blood supply: The epicranius is innervated by branches of the facial nerve (cranial nerve VII). The frontal belly is typically supplied by the temporal branches, while the occipital belly receives innervation via the posterior auricular branch. Blood supply to the region comes from branches of the superficial temporal and posterior auricular arteries, with contributions from the occipital artery to the occipital portion.

Function: Contraction of the frontalis elevates the eyebrows and wrinkles the forehead, while the occipitalis pulls the scalp backward. Coordinated activity enables expressive movements of the face, such as surprise, and helps to reposition the scalp.

Clinical significance: Lesions of the facial nerve or injuries to the galea aponeurotica can impair epicranius function, reducing the ability to raise the eyebrows or move the scalp, and thereby affecting facial expressions.