The Facial Muscle Chain Concept in Forehead Line Treatment.

Current treatment of horizontal forehead lines typically involves botulinum toxin injections targeting the frontalis muscle, though this approach may occasionally result in complications such as eyebrow ptosis. This letter introduces the facial muscle chain concept, which describes the three-dimensional anatomical relationships between facial muscles that may influence dynamic wrinkle formation. Unlike conventional muscle pairing descriptions found in existing literature, this framework explores how targeting the corrugator supercilii muscle could potentially affect frontalis muscle activity through interconnected anatomical relationships. Previous anatomical observations from cadaveric dissections demonstrate the corrugator supercilii's positioning relative to the frontalis muscle, with intermingling fibres identified at depths of 3-5 millimetres. Our clinical observations suggest that botulinum toxin injections targeting the corrugator supercilii may produce changes in horizontal forehead lines without direct frontalis muscle treatment. This approach appears to maintain natural facial expression while addressing the aesthetic concern, potentially reducing the risk of complications associated with direct frontalis injection. The facial muscle chain concept may have broader applications beyond forehead treatment, as similar interconnected relationships appear to exist between other facial muscle groups. This theoretical framework suggests that facial muscles function as an integrated system rather than isolated units, which could inform individualized injection strategies based on patient-specific anatomical variations. We present these observations to the aesthetic medicine community for consideration and further investigation. Future research utilising advanced imaging techniques and comparative outcome studies would be necessary to fully evaluate the clinical significance of this approach and establish evidence-based treatment protocols for potential integration into aesthetic medicine practice.Level of Evidence V This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .