Breast ptosis is one of the most common conditions treated by plastic surgeons. Inferomedial muscle fibers of the pectoralis major originate on the medial aspect of the sternum and rib cartilage and extend upward and laterally to insert onto the bicipital groove of the humerus. Targeting these fibers with botulinum toxin therefore results in unopposed muscular contraction upwards and toward the shoulder, with consequent elevation of the superior portion of the ptotic breast. Treatment induces breast elevation at one week and persist for 3–4 months.

This chapter details the anatomy of the breast and underlying musculature, using detailed cutaway illustrations, discusses the different degrees of breast ptosis along with patient selection and illustrates the injection sites for botulinum toxin, listing recommended doses for the different toxin preparations. Additional uses for botulinum toxin, including treatment of pectoral muscle spasm, postmastectomy pain syndrome, facilitation of breast reconstruction, pseudo-gynecomastia, and anterior mid-chest wrinkles, are discussed.