Motor Innervation and Nerve Pathway of Glabellar Expression Muscles

ABSTRACT

We studied the motor innervation and the nerve pathway of glabellar expression muscles and a kind of glabellar skin wrinkles. Electric stimulation and surface tracing of the temporal and zygomatic branches of the facial nerve was performed using an electric nerve stimulator on both sides of 14 healthy volunteers. Micro- dissection of four cadaveric heads were also performed to confirm the results of nerve stimulation test. The corrugator supercilii muscle is innervated by the temporal branch of the facial nerve. The depressor supercilii muscle, the medial head of the orbicularis oculi muscle, and the procerus muscle are innervated by the zygomatic branch. The temporal branch to the corrugator supercilii muscles travels in a curvilinear pattern superior to the upper margin of the eyebrow. The zygomatic branch to the glabellar expression muscles travels in a curvilinear pattern inferior to the inferior orbital rim in the proximal portion and in a cobwebby pattern medial to the medial orbital rim in the distal portion. In cadaveric study, the zygomatic nerve branches off in the inferomedial orbital portion, and its fine branches enter into the procerus muscle, the depressor supercilii muscle, and the orbicularis oculi muscle. The surface pathway of the motor nerve to the glabellar expression muscles is described. We think that the zygomatic and temporal branches both should be blocked simultaneously to improve glabellar skin wrinkles completely.