Abstract
The aim of this study was to determine how the depressor supercilii (DS) connects to the levator labii superioris alaeque nasi (LLSAN) and inferior fibers of the orbicularis oculi (OOc INF) in the human midface. While grimacing, contraction of the DS with fibers connecting to the LLSAN and OOc INF can assist in pulling the medial eyebrow downward more than when these connecting fibers are not present. Contraction of these distinct connecting fibers between the DS and the LLSAN can also slightly elevate the nasal ala and upper lip. The DS was examined in 44 specimens of embalmed adult Korean cadavers. We found that the DS connected to the LLSAN or the OOc INF by muscle fibers or thin aponeuroses in 33 (75.0%) of the 44 specimens. The DS was connected to both the LLSAN and OOc INF by muscle fibers or aponeuroses and had no connection to either in 5 (11.4%) and 11 (25.0%) specimens, respectively. The DS was connected to the LLSAN by the muscle fibers and thin aponeuroses in 6 (13.6%) and 4 (9.1%) specimens, respectively. The DS was connected to the OOc INF by the muscle fibers and thin aponeuroses in 5 (11.4%) and 23 (52.3%) specimens, respectively. Our findings regarding the anatomical connections of the glabellar region DS to the midface LLSAN and OOc INF provide insights on the dynamic balance between the brow depressors such as the DS and brow-elevating muscle and contribute to understanding the anatomical origins of individual variation in facial expressions. These results can also improve the safety, predictability, and aesthetics of treatments for the glabellar region with botulinum toxin type A and can be helpful when performing electromyography.
Highlights
The mimetic muscles are an assemblage of striated skeletal muscles that are innervated by the facial nerve and that control a broad range of voluntary and involuntary movements such as frowns and smiles, which are essential forms of non-verbal communication among humans
The depressor supercilii (DS) was connected to the levator labii superioris alaeque nasi (LLSAN) or the orbicularis oculi (OOc) INF by muscle fibers or aponeuroses in 33 of the 44 (75.0%) specimens
The DS was connected to the LLSAN by muscle fibers and thin aponeuroses in 6 (13.6%) and 4 (9.1%) of the 44 specimens, respectively (Fig 1)
Summary
The mimetic muscles are an assemblage of striated skeletal muscles that are innervated by the facial nerve (i.e., cranial nerve VII) and that control a broad range of voluntary and involuntary movements such as frowns and smiles, which are essential forms of non-verbal communication among humans. The corrugator supercilii (CS) is a small pyramidal muscle located at the medial end of each eyebrow, lying deep to the frontalis and orbicularis oculi (OOc). The depressor supercilii (DS) originates from the frontal process of the maxilla and inserts into the skin in the medial third of the eyebrow and into the OOc complex. The frontalis of the occopitofrontalis arises from the epicranial aponeurosis and inserts into the skin of the eyebrow and the root of the nose. The LLSAN arises from the upper part of the frontal process of the maxilla, and it descends to insert partly into the ala of the nose and partly into the skin of the lateral half of the upper lip. The LLSAN raises the lateral half of the upper lip and the wing of the nose [2–4]
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