Harnessing the Bidirectional Feature of the Frontalis Muscle: The Super-High Injection Technique.

[BACKGROUND] Botulinum neurotoxin (BoNT) is widely used for forehead rejuvenation, but risks complications like brow ptosis with conventional pan-frontalis injections. Recent study highlights the frontalis muscle's bidirectional movement, demarcated by the line of convergence (C-line): The upper segment depresses the hairline and the lower segment elevates the brows. This study evaluates the efficacy and safety of a super-high BoNT injection technique, selectively targeting the upper frontalis above the C-line to reduce forehead lines while preserving brow position and mobility.

[METHODS] Forty-one East Asian participants (35-50 years) received BoNT injections (20 U/ml) at two midline points above the C-line (upper 1/5 of the forehead). Doses varied by gender (1.5-2 U/point). Three-dimensional stereophotogrammetry quantified brow position (BP), maximal brow height (MBH), and brow movement range (BMR) at baseline , 4 weeks, and 16 weeks. Forehead Wrinkle Scale (FWS) scores and patient-reported outcomes were analyzed.

[RESULTS] At T1, static FWS improved by 51% (1.00 ± 0.70 to 0.49 ± 0.50, p < 0.01) and dynamic FWS by 63% (2.51 ± 0.64 to 0.92 ± 0.64, p < 0.01), with 100% patient satisfaction. BP decreased marginally (left: 60.83 ± 3.21 mm to 60.44 ± 3.22 mm; right: 61.06 ± 2.95 mm to 60.69 ± 3.12 mm; p < 0.05), but BMR remained stable (p > 0.1), indicating preserved dynamic function. No brow ptosis or eyelid heaviness occurred. Static and dynamic FWS scores decreased by 51% (1.00 ± 0.70 to 0.49 ± 0.50, p < 0.01) and 63% (2.51 ± 0.64 to 0.92 ± 0.64, p < 0.01), respectively.

[CONCLUSION] The super-high injection technique effectively reduces forehead wrinkles without disrupting brow dynamics, offering a safe alternative to pan-frontalis approaches. The absence of complications and preserved movement validated this anatomically guided approach as an alternative option for forehead rejuvenation.

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