Background: Individualized neuromodulator injections of the forehead are increasingly important to maximize patient safety and satisfaction and to yield the best aesthetic outcome. To assess the location of maximal muscle contraction, it would beneficial to relate the shape and location of the forehead lines to the morphology of the underlying frontalis muscle.

Materials and Methods: We investigated the shape of forehead lines and their relationship to the morphology of the underlying frontalis muscle using anatomic dissection in a sample of 31 human body donors, with a mean age at death of 77.2 ± 13.2 years (range, 47-93) of which n=29 (93.5%) were of Caucasian and n=2 (6.5%) of African-American ethnicity and of which n=16 (51.6%) were females (n=15 males; 48.4%).

Results: Horizontal forehead lines were classified into straight n=13 (41.9%) and wavy n=18 (58.1%) lines. The presence of wavy forehead lines (as compared to straight lines) was significantly related to the presence of a midline aponeurosis (r = 0.69; P less than 0.001) and to a greater muscle fascicle angle (12.67 ± 2.60° vs 10.18 ± 2.12°) (r = 0.47; P less than 0.001), but was not statistical significantly influenced by age, gender, or ethnicity (all P greater than 0.05).

Conclusion: According to the shape of the forehead lines, physicians can appreciate the morphology of the underlying frontalis muscle. This understanding will facilitate more accurate neuromodulator injections and a better aesthetic outcome. It may also result in decreased dosages and increased injection intervals for maximal patient safety. LEVEL OF EVIDENCE: IV

J Drugs Dermatol. 2017;16(5):471-477.