The process of scar formation is denoted by three stages: inflammatory, proliferative, and remodeling. The former phase is characterized by the activation of the extrinsic clotting pathway and subsequent materialization of a fibrin plug, after which neutrophils facilitate the degradation of pathogens and secretion of signaling molecules that commence the proliferative phase. The fibrin plug is then replaced by granulation tissue comprised of macrophages, fibroblast, and endothelial cells in the proliferative phase. Through the release several growth factors, existing macrophages induce laying down of type III collagen by fibroblasts, and keratinocytes work in tandem to approximate wound edges. Lastly, during the remodeling phase, cellular apoptosis causes granulation tissue formation to subside, type III collagen is replaced by a more durable collagen type I, and myofibroblasts help to condense the scar size.1,2~While scarring in its non-pathological forms is an innate and appropriate bodily response to cutaneous injury, scar development and persistence can have negative physical and psychological implications, including decreased range of motion secondary to contracture, disfigurement, and impaired quality of life.1,3-5 Thus, for medical and cosmetic purposes alike, curtailing scar formation is important aspect of patient management, and treatment aimed at both prevention and resolution is an evolving subject in the medical discourse. Credence has been given to the use of botulinum toxin A (BTA) in scar minimization, a more novel therapy, and has proved efficacious in several studies including those examining BTA in the treatment of keloids and hypertrophic scars, mammoplasty and abdominoplasty surgery scars, and post-operative scars generally.6-9 The suggested mechanisms for this phenomenon involve inhibition of pre-synaptic acetylcholine channels that lead to muscle paralysis and relaxation of perpendicular wound tension; this particular mechanism is likewise theorized to mitigate collagen overproduction. Another hypothesis for explaining the ability of BTA to reduce scar appearance is the direct modulation of fibroblast activity.6
The proposed study seeks to evaluate the scar reduction capacity of BTA on excision/biopsy wounds compared to the control (normal saline) in a double-blinded randomized control trial. It will expand upon previous studies that have already demonstrated the safety and good tolerance profile of BTA. We will be conducting a split-scar study/study involving two biopsy sites in a singular patient, allowing them to serve as their own control. In keeping with the results from previously conducted studies, we hypothesize that the wounds treated with BTA will have significantly less evidence of scar formation than those sites treated with normal saline.