CHAPTER 42 Neurotoxins in Males
Summary
This chapter outlines the differences of the cosmetic use of botulinum toxin in males and in females. The subject is addressed in an anatomical manner with appropriate references.
Introduction
Injectable botulinum toxin type A (BoNTA) is one of the main drivers of any cosmetic practice and is the single most common cosmetic procedure performed in men. While injection techniques are similar for both sexes, it is important to recognize and identify anatomical differences in the male facial skeleton and subcutaneous tissues that may affect clinical outcome. Careful patient assessment and attention to proper dosing, along with a clear understanding of gender-based aesthetic ideals, is key to achieving success with BoNTA in men.
Botulinum Neurotoxin
One of the seven serotypes derived from the bacterium Clostridium botulinum and one of the deadliest toxins known to humanity, BoNTA has become the most popular minimally invasive cosmetic procedure performed worldwide. BoNTA produces temporary muscle paralysis by binding to presynaptic cholinergic nerve terminals and blocking the release of acetylcholine at the neuromuscular junction. The clinical effect lasts an average of 3 to 6 months before the muscles regain function, although regular, repeated treatments tend to extend the duration of effect.
BoNTA was first tested in primates in the late 1970s for the treatment of strabismus and has been used for a wide range of therapeutic applications for over 30 years. The cosmetic benefits, discovered serendipitously in the late 1980s, continue to expand. Used primarily to reduce the appearance of fine lines and wrinkles caused by hyperdynamic muscles, BoNTA is also capable of correcting asymmetries and shaping the face.
There are three formulations of BoNTA that have been approved in the United States by the Food and Drug Administration for cosmetic use: onabotulinumtoxinA (onaA; Botox Cosmetic, Allergan, Irvine, CA), abobotulinumtoxinA (Dy-sport, Valeant Pharmaceuticals International, Montreal, Canada), and incobotulinumtoxinA (Xeomin, Merz Pharmaceuticals, Frankfurt, Germany). Dosing discussed in this chapter refers specifically to the onaA formulation ( Fig. 42.1 ), with which we have the greatest experience.
Physical Evaluation
The key to successful treatment with BoNTA is individualized patient assessment. Comprehensive facial assessment encompasses both static and dynamic observation and allows the clinician to watch the muscles at work, reveal any asymmetries or contraindications to treatment, and formulate an individual treatment plan designed to achieve aesthetic goals. The most accurate pretreatment evaluation is obtained through observation of spontaneous animation during the initial consultation while clinician and patient are in dialogue. Wrinkle reduction is considered within the framework of overall facial enhancement. Muscles of facial expression have complex anatomical and physiological interactions and are rarely treated in isolation.
Anatomy
Aging and the Male Face
Sexual dimorphism in facial anatomy and cutaneous physiology is well documented, and these differences affect the aging process and its associated treatment with BoNTA. The male skull is larger, but there are also differences in skeletal landmarks and overall cranial shape. Men tend to have a large forehead with prominent supraorbital ridges, eyebrows that sit low on the orbital ridge, a wide glabella, square orbit, flatter, more angular cheeks, and a prominent, protruding mandible. Facial muscles are larger and tend to be more dynamic, with a greater amount of movement on animation. Although male skin is thicker at all ages and is associated with increased sebum and sweat production, there is less subcutaneous fat, particularly in the cheeks. The male face is highly vascularized and more prone to develop bruising, especially in the lower face around the mouth and neck.
These anatomical variations contribute to the way in which men age. Greater muscle movement, combined with loss of adipose tissue and thicker skin, results in deeper lines of expression in the upper two-thirds of the face. Men tend to have more severe wrinkles than women, except in the perioral region. More-over, aging causes a downward shift of the lower eyelid that is significantly more severe in older men than in women.
Botulinum Toxin and Men
BoNTA is the single most requested cosmetic procedure in men. According to 2015 statistics from the American Society of Plastic Surgeons, the number of men seeking BoNTA injections has increased by 355% since the year 2000. Treatment requires an overall assessment of anatomical landmarks, muscle size and movement, and desired outcomes, taking into consideration two important factors: aesthetic ideals and proper dosing. As in women, the goal is not to paralyze muscles completely, but to gently reduce hyperactivity. The use of BoNTA in men is inadequately studied with regard to dosing, efficacy, and safety. However, close analysis of data that do exist highlights the need for higher doses in men to achieve optimal results because of size and strength of target muscles. Indeed, underdosing is the most common cause of inadequate results. Male facial anatomy—the shape of the skull and its various landmarks such as brow position and strong jaw—helps define aesthetic goals. To that end, a thorough understanding of the underlying facial musculature and the physiological interactions of the muscles is critical to success, especially in the upper face.
Patient Selection
Not all men are good candidates for neurotoxin. Patients who present with severe, deep wrinkles may have unrealistic expectations and may require additional interventions to achieve treatment goals, such as soft-tissue fillers or resurfacing. BoNTA is contraindicated in the presence of infection at the site of injection and in individuals with known hypersensitivity to any ingredient in the formulation. Caution is advised in patients with the following disorders:
Peripheral motor neuropathic diseases or neuromuscular functional disorders.
Those at risk of clinically significant systemic side effects.
Coadministration with aminoglycoside antibiotics or other agents that interfere with neuromuscular transmission, which may potentiate the effect of BoNTA.
Inflammatory skin conditions at the site of injection.
Treatment Considerations and Steps for BoNTA Usage
BoNTA in the Upper Face
Growing evidence suggests that regular, repeated treatment with BoNTA in the upper face prevents new wrinkle formation and leads to continual, sustained improvements in the appearance of deep, static rhytids. The position and shape of eyebrow are central to the aesthetic evaluation of the face, particularly in men, and should be considered in advance of any and all treatments with BoNTA in the upper face. Typically, women have a more arched eyebrow, which is considered to be aesthetically pleasing, while men accept and prefer a flatter, less arched brow. Because treatment of the glabella, forehead, and crow’s feet regions can individually alter eyebrow shape and position, they are often assessed and treated together, aiming for balance and harmony.
Glabellar Rhytids
Glabellar rhytids, or vertical frown lines between the eyes (“elevens”), were the first wrinkles to be treated with BoNTA and remain one of the greatest cosmetic concerns for both men and women. The interplay of musculature in the glabellar complex—the corrugator supercilii, which moves the brow medially, the procerus and depressor supercilii, which pull the brow inferiorly, and the orbicularis, which moves the brow medially—is critical for the shape and position of the eyebrow. Treatment of the depressor supercilii fibers, for example, will allow a slight elevation of the medial brow due to unopposed activity of the frontalis muscle. It is important to recognize and maintain the aesthetics of the male brow, which is flatter and less arched than the female brow, and sits lower along the orbital rim. Moreover, the muscles of the glabellar complex in men are larger and often need higher doses to achieve the same results seen in women with much smaller doses. The exact number of injection sites and distribution of doses depend on individual assessment of muscle function and aesthetic goals. However, consensus recommendations—and personal experience—suggest starting doses of 40 units onaA divided among seven injection sites for the male brow. Some men may require up to 100 units to achieve optimal results.
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