Topography of the Corrugator Supercilii Muscle Relative to the Eyebrow and Its Clinical Application in Botulinum Toxin Injections.

The purpose of this study was to elucidate the topography of the corrugator supercilii muscle (CSM) relative to the eyebrow with the aim of providing topographical guidance for botulinum toxin type A (BTX-A) injections in the East Asian population. Thirty-six hemifaces of 18 donated bodies for anatomical studies were dissected. Prior to dissection, four specific points on the eyebrow were marked to serve as reference points. A superimposition method for analyzing the position of the CSM relative to the eyebrow involved overlaying an image showing the dissected muscle onto a pre-existing image that contained reference lines indicating the eyebrow landmarks. The CSM almost overlaps the eyebrow at its medial end. Significantly, the central part of the CSM's width was positioned just above the upper point of the eyebrow, being closely aligned with the midpupillary line. There was minimal overlap of the CSM beyond the midpupillary line on the lateral side, indicating that this muscle becomes relatively scarce or less distinct as it extends laterally from the midpupillary line. For effectively targeting the CSM, it is recommended to inject BTX-A precisely at the center of the medial end of the eyebrow just above the midpupillary line.