Sonographic Analysis of the Upper Labial Orbicularis Oris and Its Clinical Implications

Ultrasonographic Analyses of Crow's Feet and Novel Guideline for Botulinum Toxin Injection

BACKGROUND

Crow's feet are bilateral orbital wrinkles formed by the orbital portion of the orbicularis oculi muscle, which is the target muscle for botulinum neurotoxin (BoNT) injection.

OBJECTIVES

This study's aim was to demonstrate a novel BoNT injection guideline by assessing muscle width, thickness, and dynamic features using ultrasonography.

METHODS

Twenty healthy Korean volunteers (10 men, 10 women; mean age, 25.6) participated. The width, thickness, and dynamic movement of the orbicularis oculi muscle were measured using ultrasonography. Two volunteers were selected to receive BoNT injections. Injections were administered using a novel method with two curved reference lines passing a point 15 mm lateral to the lateral canthus (conventional injection) and a point 5 mm lateral to the lateral margin of the frontal process of zygomatic bone (additional injection).

RESULT

At the lateral canthus level, the distance between the lateral margin of the frontal process and the most lateral margin of the orbicularis oculi muscle was 12.5±1.3 mm. The thickness of the orbicularis oculi muscle at the midpoint of the frontal process, the lateral marginal of the frontal process, and 5 mm lateral to the lateral marginal of the frontal process was 0.7±0.3 mm, 1.1±0.3 mm, and 1.2±0.3 mm, respectively. The crow's feet of the two volunteers began to disappear from day 3 and completely disappeared on day 7 after the injection.

CONCLUSION

The novel injection technique based on the ultrasonographic anatomy resulted in improvements in the appearance of crow's feet.

Anatomical Injection Guidelines for Glabellar Frown Lines Based on Ultrasonographic Evaluation

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.