Mechanistically, the scalp behaves like a drum skin with tensioning muscles around the periphery. These muscle groups—the frontalis, occipitalis, and periauricular muscles and to a minor degree the temporalis—can create a “tight” scalp when chronically active. Because the blood supply to the scalp enters through the periphery, a reduction in blood flow would be most apparent at the distal ends of the vessels, specifically, the vertex and frontal peaks. Areas of the scalp with sparse hair growth have been shown to be relatively hypoxic, have slow capillary refill, and to have high levels of dihydrotestosterone.4
Conceptually, Botox “loosens” the scalp, reducing pressure on the perforating vasculature, thereby increasing blood flow and oxygen concentration. The enzymatic conversion of testosterone to dihydrotestosterone is oxygen dependent. In low-oxygen environments, the conversion of testosterone to dihydrotestosterone is favored; whereas in high-oxygen environments, more testosterone is converted to estradiol.4 Blood flow may therefore be a primary determinant in follicular health. Strategically placed Botox injections appear able to indirectly modify this variable, resulting in reduced hair loss and new hair growth in some men with androgenetic alopecia.
The investigators have received support in the form of unrestricted educational grants from Allergan Inc. (Irvine, Calif.) within the past 5 years. The authors hold intellectual property rights related to the process described in this study in both the United States and the European Union. This study was not supported by any commercial entity or government agency.
Brian J. Freund, D.D.S., M.D.
Marvin Schwartz, D.D.S., M.Sc.
1. Kaufman KD, Olsen EA, Whiting D, et al. Finasteride in the treatment of men with androgenetic alopecia. Finasteride Male Pattern Hair Loss Study Group. J Am Acad Dermatol.
2. Norwood OT. Male pattern baldness: Classification and incidence. South Med J.
3. Canfield D. Photographic documentation of hair growth in androgenetic alopecia. Dermatol Clin.
4. Goldman BE. Transcutaneous PO2 of the scalp in male pattern baldness. Plast Reconstr Surg.
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