Long-lasting Relaxation of Corrugator Supercilii Muscle Contraction Induced by Near Infrared Irradiation

Objective: We previously reported that near infrared (NIR) irradiation weakens frontalis muscle contraction resulting in brow ptosis. In addition, NIR irradiation non-thermally long-lasting thinning of the panniculus carnosus muscle in rats. We sought to determine whether NIR irradiation affects contraction of the corrugator supercilii muscle (CSM). Methods: Three to 5 rounds of NIR irradiation were performed weekly to relax the CSM in 40 patients who had sustained myalgia of the CSM. Each round of irradiation consisted of 10 to 40 doses of NIR irradiation at 28 to 40 J/cm(2). We measured changes in the location of the most medial point of the eyebrow rather than evaluation of the glabellar frown line, especially in the 10 unilaterally irradiated patients. We confirmed relief of the CSM myalgia, using a visual analog scale (10 cm in length) in 40 patients. Results: The location of the most medial point of the eyebrow was significantly and durably displaced in the lateral direction when compared with that of the non-irradiated eyebrow, especially in the unilaterally irradiated patients. The visual analog scale score improved from 10 cm to approximately 3 cm in the 40 patients treated. Conclusions: NIR irradiation appeared to induce long-lasting relaxation of the CSM, resulting in the lateral displacement of the most medial point of the eyebrow and relief of its myalgia. Although NIR irradiation flattens skin wrinkles by dermal thickening, it may also non-thermally relax the underlying superficial muscles to reduce wrinkles and myalgia.