The occipitofrontalis muscle is composed of two physiologically and anatomically different muscles separately affecting the positions of the eyebrow and hairline

After the surgical correction of aponeurotic blepharoptosis or blepharoplasty, the positions of the eyebrow and hairline change as if the frontal belly is independent from the occipital belly of the occipitofrontalis muscle. Therefore, the occipitofrontalis muscle was studied physiologically with electromyographic evaluation in healthy subjects and anatomically with cadaver dissections. Along with contraction of the levator muscle to maintain an adequate visual field, at a less upward gaze position, contraction of only the frontal belly was induced, and at a more upward gaze position, contraction of both the frontal and the occipital bellies was always induced to lift the eyebrow with the upper eyelid skin. The superficial fascia overlying the occipital belly becomes the temporoparietal fascia and ends at the superior end of the frontal belly, thus creating a superficial musculoaponeurotic system that lifts the eyebrow and pulls the scalp forwards. Beneath the superficial musculoaponeurotic system, the occipital belly of the occipitofrontalis muscle becomes the galea aponeurotica and inserts into the underside of the frontal belly, thus creating a deep musculoaponeurotic system that pulls the superficial musculoaponeurotic system with the scalp backwards. Thus, the occipitofrontalis muscle appears to be composed of two physiologically and anatomically different muscles.