Abstract
When botulinum neurotoxin (BoNT) is injected to treat glabellar frown lines, the corrugator supercilia muscle (CSM) and procerus muscles are the main targets. Although there have been many studies on the treatment of glabellar frown lines, no study has confirmed the dynamic movement under ultrasonography (US). This study examined and evaluated dynamic muscle movements under US, thereby providing more effective BoNT injection guidelines for glabellar frowning. Glabellar frowning was categorized as either Type A or B. Type A is the general frowning pattern in which vertical wrinkles are made by contracting the CSM and procerus muscles (81%, n = 13). On US images, the procerus muscle thickens and the bilateral CSMs contract. Type B is an upward frowning pattern demonstrating upward elevation of vertical wrinkles due to hyperactive contraction of the frontalis muscle during frowning (19%, n = 3). On US images, the hypoechoic frontalis muscle thickens, forming horizontal forehead lines. After BoNT injection into the CSM and frontalis muscle but not the procerus muscle, Type B patterns showed improvements in the vertical crease and horizontal forehead line. Both types showed improvement in glabellar frown lines after conventional injection, but the horizontal forehead line did not improve in Type B. Type B wrinkles improved after additional injections into the frontalis muscle. This study provided novel anatomical findings related to the injection of glabellar frown lines with BoNT. Preliminary analysis and optimized procedures using US will enable more effective and safer injections.
Highlights
US-Based of the Frowning a general frowning pattern in which vertical wrinkles are formed by the contraction of Glabellar frowning was categorized into two patterns according to US
On the US images, the procerus muscle general frowning pattern in which vertical wrinkles are formed by the contraction of the thickens as a hypoechoic image and the bilateral corrugator supercilii muscles (CSM) contract (Figure 1A)
Despite many studies on the efficacy and safety of botulinum neurotoxin (BoNT) injection procedure for the correction of glabellar frown lines [5,8,9,10], there have been no studies suggesting more effective injection guidelines based on the dynamic anatomical changes of the facial muscle under US
Summary
Glabellar frown lines are generally created by the frontalis, the procerus, and the corrugator supercilii muscles (CSM), and are esthetically unattractive and may result in the individual appearing older than they are or giving a negative facial expression [1]. Based on the anatomical features contributing to glabellar frown lines, the general side botulinum (BoNT). Botulinum neurotoxin (BoNT) injection procedure has glabellar lines, the general are individual differences in facial expression been There performed in the CSM and procerus muscles [2,3]. It isexpression essential due to evaluate dynamic anatomical are individual differences in facial to facial muscle variations and changes in of facial muscles [4]. It is essential toevaluation-based evaluate dynamiccustomized anatomicaltreatments changes in are very helpful inIn meeting the patient demands of patients achieving optimal results [5].are.
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