Pathogenesis and surgical correction of involuntary contraction of the occipitofrontalis muscle that causes forehead wrinkles.

Assuming that an agonistic function is present to maintain an adequate visual field, we hypothesized that stretching of the mechanoreceptor of Mueller muscle induces involuntary contraction of the occipitofrontalis muscle, as well as the levator muscles. In patients with aponeurotic blepharoptosis, both unilateral instillation of phenylephrine to contact Mueller smooth muscle fibers and unilateral aponeurotic fixation ipsilaterally reduced the eyebrow height during primary and upward gazing. Bilateral aponeurotic fixation bilaterally reduced the eyebrow height, with fewer forehead wrinkles. Stretching of the mechanoreceptor of Mueller muscle induces involuntary contraction of the bilateral levator muscles. Its increased stretching may induce involuntary contraction of the ipsilateral occipitofrontalis muscle via the mesencephalic trigeminal nucleus and the facial subnucleus as another stretch reflex. The involuntary contraction of the occipitofrontalis muscle that causes forehead wrinkles during primary gazing can be corrected by the aponeurotic fixation to reduce the stretching of Mueller muscle.