Top 8 Indications of Neurotoxins in Non-Surgical Facial Rejuvenation
In the intricate realm of aesthetic medicine, neurotoxins have emerged as indispensable tools, offering precise and effective solutions for facial rejuvenation and the management of various neuromuscular disorders. Rooted in the intricate interplay between neurophysiology and pharmacology, neurotoxin therapy represents a sophisticated approach to modulating neuromuscular signaling, thereby achieving targeted muscle relaxation and functional improvement. By selectively inhibiting the release of acetylcholine at the neuromuscular junction, neurotoxins disrupt the communication between motor neurons and muscle fibers, leading to temporary muscle paralysis and subsequent attenuation of dynamic wrinkles and hyperfunctional muscle activity. This intricate mechanism of action underpins the therapeutic versatility of neurotoxins, extending beyond aesthetic applications to encompass therapeutic interventions for conditions such as spasticity, dystonia, and migraine headaches. With a nuanced understanding of neuroanatomy, injection techniques, and patient-specific considerations, clinicians harness the therapeutic potential of neurotoxins to sculpt natural, harmonious outcomes, optimizing patient satisfaction and quality of life.
In this blog, we will discuss 8 distinct indications of neurotoxins, along with the potential complications associated with their administration
What are Their Indications in Each Facial Part?
a) Upper Face
Neurotoxins are commonly employed in non-surgical facial rejuvenation, particularly in the upper face, to mitigate wrinkles resulting from muscular contractions. The orbicularis oculi, a substantial muscle extending beyond the orbital rim, gives rise to lateral canthal lines known as crow's feet. When treating these lines, injections should not extend more medially than the lateral extent of the orbital rim to avert complications such as diplopia and strabismus arising from paralysis of the lateral rectus muscle. The administration of neurotoxins for crow's feet typically involves injecting up to 15 units of onabotulinum, incobotulinum, prabotulinumtoxin, or up to 45 units of abobotulinum per side in 3–4 sites within the muscle, positioned at least 1 cm lateral to the lateral orbital rim to minimize intraorbital complications.
1. Addressing Aging Face & Lines
The application of neurotoxins in addressing facial wrinkles and lines involves a sophisticated understanding of neurophysiology, pharmacology, and facial anatomy. Neurotoxins, such as botulinum toxin type A, exert their therapeutic effects by selectively inhibiting the release of acetylcholine at the presynaptic nerve terminals within the neuromuscular junctions.
In the context of facial wrinkles and lines, neurotoxins are strategically injected into specific facial muscles responsible for dynamic muscle contractions and repetitive facial expressions. These muscles, including the corrugator supercilii, procerus, and orbicularis oculi, contribute to the formation of dynamic wrinkles, such as glabellar lines (frown lines), forehead lines, and crow's feet, through repetitive contraction and relaxation.
Upon injection, neurotoxins bind to the presynaptic nerve terminals, where they undergo internalization and subsequent cleavage of specific proteins involved in neurotransmitter release, namely SNAP-25. This process effectively blocks the release of acetylcholine, the neurotransmitter responsible for muscle contraction, leading to temporary muscle paralysis and functional denervation of the injected muscles.
By inducing muscle relaxation and reducing muscle activity, neurotoxins prevent the formation of dynamic wrinkles and soften the appearance of existing lines. Furthermore, the attenuation of muscle hyperactivity minimizes mechanical stress on the overlying skin, allowing for gradual skin smoothing and wrinkle reduction over time.
The therapeutic efficacy of neurotoxins in addressing facial wrinkles and lines is contingent upon several factors, including precise injection technique, dosage, and patient-specific considerations. Clinicians must possess a thorough understanding of facial anatomy and muscle dynamics to accurately identify target muscles and optimize treatment outcomes.
2. Brow Rejuvenation
In brow rejuvenation, neurotoxins play a crucial role. Gender-specific aesthetic and anatomic differences are considered when planning facial rejuvenation. Ideal male and female brows have distinct characteristics, and the administration of neurotoxins requires a balance between muscle forces to maintain an aesthetically pleasing brow position. The muscles involved in brow movement, such as the frontalis, corrugator supercilii, depressor supercilii, procerus, and the orbital portion of the orbicularis oculi, are carefully addressed during treatment. The recommended injection points for frontalis treatment involve a 'Jacob's ladder' distribution to prevent brow ptosis and asymmetry. Careful consideration of the lateral fibers of the frontalis muscle is crucial to avoid unwanted effects, such as 'eyebrow commas' or a drooping brow, ensuring a natural and harmonious outcome.
The administration of neurotoxins for the corrugator supercilii poses a nuanced challenge. Treating this muscle in proximity to its origin necessitates a deeper injection to encompass its medial portion and the depressor supercilii muscle. In contrast, lateral injections should be slightly more superficial as the muscle approaches the dermis. Typically, 16–20 units of onabotulinum, incobotulinum, prabotulinum, or 48–60 units of abobotulinum are required for the corrugator supercilii. The glabellar complex typically requires 20–25 units of onabotulinum, incobotulinum, prabotulinum, or 60–75 units of abobotulinum, with specific injection sites targeting the procerus and corrugators. Due to the interdigitation of the frontalis with brow depressors, careful consideration is given to prevent unwanted spread of neurotoxin to the frontalis. This involves using a concentrated neurotoxin (1–2 cc reconstitution), injecting low on the procerus and medial belly of the corrugators, and ensuring precise lateral injection points to prevent medial brow ptosis.
Contraction of the pretarsal orbicularis oculi during smiling can lead to a 'jelly-roll' deformity, resulting in a subciliary bulge. This can be effectively treated with 2 units of incobotulinum, onabotulinum, prabotulinum, or 6 units of abobotulinum, injected 3 mm below the mid-pupillary line subcutaneously. The treatment enhances the aesthetic appearance by reducing the muscle bulge and widening the palpebral aperture, resulting in a more alert and wide-eyed look. A simple snap test can aid in determining candidacy for this injection.
Eyelid ptosis is a notable side effect of neurotoxin use in the upper third of the face. While initial reports suggested an incidence of approximately 5%, recent studies indicate a reduced occurrence of this complication. Ptosis can manifest up to 2 weeks post-injection and results from neurotoxin migration to the levator palpebrae superioris muscle. To mitigate ptosis, injections should be administered at least 1 cm above the superior orbital rim and should not cross the mid-pupillary line. Apraclonidine 0.5% eye drops are recommended for treating neurotoxin-induced ptosis, causing Müller muscles to contract and elevating the upper eyelid by 1–3 mm. Additionally, naphazoline, another a2-adrenergic agonist, can be used for this purpose.
3. Reshaping the Forehead
The forehead is composed of several superficial and deep muscles responsible for various facial expressions, including raising the eyebrows, wrinkling the forehead, and maintaining brow position. Among these muscles, the frontalis muscle plays a central role in forehead movement and contour. Contraction of the frontalis muscle results in vertical elevation of the eyebrows and the formation of horizontal forehead lines, commonly known as "worry lines" or "forehead wrinkles." Reshaping the forehead with neurotoxins is achievable by addressing temporalis muscle hypertrophy. While not a facial expression muscle but a mastication muscle, hypertrophy of the temporalis can impart an unconventional shape to the forehead. Neurotoxins are strategically injected into the frontalis muscle to induce muscle relaxation and attenuate its dynamic activity.
b) Midface
The midface, delineated as the region spanning from the zygomatic arch and malar eminence to the nasolabial fold, is traditionally addressed using fillers for aesthetic enhancement. However, neurotoxins have emerged as increasingly pivotal in augmenting aesthetics in this particular region.
1. Addressing Bunny Lines
One notable midface muscle is the nasalis, responsible for centrally and vertically oriented dynamic rhytids referred to as "bunny lines." Administration of 2–3 units of onabotulinum, incobotulinum, prabotulinum, or 6–9 units of abobotulinum on each side of the nose, midway between the cheek–nose junction and nasal dorsum, effectively addresses these dynamic lines. Precision in injection placement is crucial to avoid lip ptosis, smile asymmetry, and complications such as medial rectus paresis and epiphora.
2. Addressing Nasal Flaring
Neurotoxins also find unique application in addressing nasal flaring, which conveys subconscious emotions such as anger, fear, exhaustion, concern, or distress. Utilizing 4–10 units of onabotulinum, incobotulinum, prabotulinum, or 12–30 units of abobotulinum in the center of each alar rim yields optimal results, particularly in patients who can actively dilate their nostrils.
3. Addressing Canine Smile
Moving to the mouth area, patients presenting with a "canine smile" or "gummy" smile, attributed to heightened tone in the levator labii superioris and levator labii superioris alaeque nasi, benefit from targeted neurotoxin injections. Administering 1–2 units of onabotulinum, incobotulinum, prabotulinum, or 3–6 units of concentrated abobotulinum to the levator labii superioris alaeque nasi, and 2–4 units of onabotulinum, incobotulinum, prabotulinum, or 6–12 units of concentrated abobotulinum to the levator labii superioris, effectively corrects the gummy smile. Moreover, neurotoxin injections can address an asymmetric smile caused by hypertonicity of the depressor anguli oris (DAO), a muscle responsible for the downward pull of the oral commissure. Successful intervention involves 4 units of onabotulinum, incobotulinum, prabotulinum, or 12 units of abobotulinum to each DAO and 4 units to the levator labii superioris alaeque nasi. Nasolabial fold filler treatments may complement these interventions, although caution is urged to avoid asymmetrical smiles resulting from excessive dosing and medial injections that may lead to depressor labii inferioris muscle paralysis.
c) Lower Face
The lower face has emerged as a focal point for neurotoxin therapy, presenting both popularity and challenges in its rejuvenation efforts. While volume replacement and wrinkle reduction have traditionally dominated this domain, the role of neurotoxins is increasingly significant. The central portion of the lower face is predominantly governed by the orbicularis oris muscle, intricately connected to the dermis of the lip's glabrous skin. Repetitive actions like puckering, smoking, or using a straw contribute to the development of perioral lines, prompting the use of neurotoxin therapy. A recommended approach involves employing 3–4 units of onabotulinum, incobotulinum, prabotulinum, or 9–12 units of abobotulinum in the upper lip and 2 units of onabotulinum, incobotulinum, prabotulinum, or 6 units of abobotulinum in the lower lip. Precision in injection placement, with one-unit aliquots over specific vermilion border points, is crucial to avoid unintended spread and achieve optimal results.
Moving to the mentalis, a frequently injected area for aesthetic purposes in the lower face, this muscle can cause skin dimpling with elevation, commonly referred to as cobblestoning or peau d'orange. Additionally, it can create a prominent mental crease, contributing to an undesirable appearance. A single injection in the midline of 4–10 units of onabotulinum, incobotulinum, prabotulinum, or 12–30 units of abobotulinum is commonly performed. Bilateral injections on either side of the midline can also be considered, with 4–5 units per injection site for onabotulinum, incobotulinum, prabotulinum, or 12–15 units of abobotulinum. These treatments can be complemented with multimodal therapy involving fillers and neurotoxins.
Further addressing the lower one-third of the face, the Masseter muscle, situated laterally, plays a significant role in facial reshaping. Its hypertrophy can result in a squared mandible, contributing to a more masculine appearance, or an oval shape, associated with a more feminine look. This condition may be linked to malocclusion, temporomandibular joint dysfunction, or bruxism, and the impact is observable across various ethnic backgrounds, being more prevalent in certain populations, such as Korean women. During Masseter treatment, patients are instructed to bite down, facilitating the injection process by creating a firm muscle mass. A dosage ranging from 10–40 units of onabotulinum, incobotulinum, prabotulinum, or 30–120 units of abobotulinum is administered. Follow-up assessments are conducted to determine the need for further injections, and the atrophy induced by adequate dosing can persist for six to nine months. Notably, patients experiencing both masseter hypertrophy and temporomandibular joint symptoms often report relief from their symptoms. It is imperative to exercise caution during injection, especially in front of the anterior border of the masseter, to avoid complications such as weakness of the risorius and an asymmetric smile.
e) Neck
Moving to the neck, a region increasingly considered for neurotoxin treatment, the principal muscle of concern is the platysma, a major depressor in the lower face. The intricate insertions of the platysma enable it to exert a downward pull on both cheek skin and the corners of the mouth. Precision in injecting vertical platysmal bands with neurotoxin serves to counteract the downward motion vector, creating a net upward vector facilitated by the lateral facial extent of the platysma muscle and the midface elevators. This approach contributes to enhanced definition of the jawline. A recommended dosage entails 2.5 units of onabotulinum, incobotulinum, prabotulinum, or 7.5 units of abobotulinum every 1.5 cm along the vertical bands of the platysma, with multiple bands identified and treated during contraction. The Nefertiti lift, a specific technique, involves targeting the crucial contractile band of the platysma extending into the jowl, accompanied by selected injections along the mandible. Injecting the medial vertical bands additionally allows for the creation of a more pronounced cervicomental angle, overcoming blunting effects caused by these bands.
During the injection process of platysmal bands, optimal technique involves grasping the contracted band between the thumb and index finger, injecting tangentially to the skin's surface to prevent the spread of neurotoxin to deeper neck muscles. Vigilance against improper injection technique and excessive dosing (beyond 50 units of onabotulinum, incobotulinum, prabotulinum, or 150 units of abobotulinum) is crucial in avoiding complications such as dysphagia and dysphonia.
Necklace lines, also known as tech lines, pose a unique challenge for singular modality treatment. These horizontal lines traverse the neck within flexion creases and are best addressed through a combination of neurotoxins and low-viscosity hyaluronic acid. Conservative resurfacing techniques can also contribute to effective treatment. The recommended injection involves 1 unit of onabotulinum, incobotulinum, prabotulinum, or 3 units of abobotulinum, spaced one centimeter along the necklace line from the midline of the neck to the medial border of the sternocleidomastoid muscle, complemented by filler injection. This comprehensive approach ensures a multifaceted solution for challenging neck aesthetics.
Potential Complications
However, the cosmetic application of botulinum toxin is not without its potential complications. Utilizing the smallest effective dose in the upper third of the face is advisable to mitigate adverse outcomes like asymmetry, lid or brow ptosis, and mouth asymmetry. Careful consideration of the spread of effect is essential, as different neurotoxins exhibit varying spread characteristics.
Injection Site Reactions: Injection site reactions are common complications following neurotoxin administration and may include erythema (redness), swelling, bruising, and pain at the injection site. These reactions are typically mild and transient, resolving within a few days to weeks post-treatment. However, improper injection technique or needle placement can increase the risk of more severe reactions, such as hematoma formation or tissue necrosis
Muscle Weakness or Paralysis: Neurotoxins induce muscle weakness or paralysis by inhibiting the release of acetylcholine at the neuromuscular junctions. While this effect is desired for therapeutic purposes, excessive dosage or improper injection technique can lead to unintended muscle weakness or paralysis beyond the targeted area. This can result in asymmetrical facial expressions, drooping eyelids (ptosis), or difficulty in facial movements, impacting both aesthetic and functional outcomes.
Ptosis: Ptosis, or drooping of the eyelid, is a common complication associated with neurotoxin injections, particularly when administered in the periorbital region for the treatment of crow's feet or forehead lines. Ptosis occurs due to the diffusion of neurotoxin into adjacent muscles responsible for eyelid elevation, such as the levator palpebrae superioris muscle. Improper dosage or injection technique can lead to excessive weakness of these muscles, resulting in ptosis and visual impairment.
Eyebrow or Lip Asymmetry: Neurotoxin injections aimed at relaxing specific facial muscles to reduce wrinkles or lines can inadvertently lead to eyebrow or lip asymmetry if not administered symmetrically or if dosage calculations are inaccurate. Asymmetry in facial expressions can be aesthetically displeasing and may require corrective treatments to restore balance and harmony to the facial features.
Spread of Toxin: Neurotoxins have the potential to spread beyond the intended injection site, leading to unintended muscle weakness or paralysis in adjacent areas. Factors contributing to toxin spread include improper injection depth, volume, or pressure, as well as patient-specific factors such as muscle mass and facial anatomy. Clinicians must exercise caution to minimize the risk of toxin diffusion and its associated complications.
Allergic Reactions: While rare, allergic reactions to neurotoxins or their components can occur, leading to symptoms such as rash, itching, swelling, or anaphylaxis. Clinicians should inquire about patients' medical history and allergies before administering neurotoxin injections and be prepared to manage allergic reactions promptly if they arise.
Systemic Effects: Although rare, systemic effects of neurotoxins, such as botulism-like symptoms, may occur following excessive dosage or inadvertent systemic absorption. Symptoms may include generalized muscle weakness, difficulty swallowing or breathing, and systemic muscle paralysis. Prompt recognition and management of systemic effects are essential to prevent serious complications and ensure patient safety.
Long-term Effects and Resistance: Prolonged or repeated use of neurotoxins may lead to the development of resistance, wherein muscles become less responsive to treatment over time. Additionally, long-term effects of neurotoxins on facial muscles and surrounding tissues are still under investigation, including potential changes in muscle morphology, contractility, and connective tissue remodeling.
Patients should be informed about potential adverse effects, including muscle weakness, injection site reactions, bleeding/bruising, headaches, and other complications such as trouble swallowing or breathing, double or blurred vision, ptosis of eyelids and/or brows, dysphonia, dysarthria, and loss of bladder control. Special precautions are warranted for individuals with specific allergies or motor neuropathic diseases, necessitating close monitoring during botulinum toxin administration
To minimize complications and adverse events, patients are generally advised to abstain from anticoagulants, platelet inhibitors, NSAIDs, and blood-thinning compounds for two weeks unless medically necessary. Magnification and bright illumination are recommended during injections to avoid blood vessels, and injection below the periosteum should be avoided to prevent headaches. Post-procedure, patients are advised to refrain from palpating treated areas for several hours, avoid alcohol intake and exercise for two hours, and exercise muscle groups injected with botulinum toxin every 15 minutes for two hours post-injection.
Reference:
Advanced Techniques for the Use of Neurotoxins in Non-Surgical Facial Rejuvenation (2020)
Comparison and overview of currently available neurotoxins (2014)
Relevant anatomy for botulinum toxin facial rejuvenation (2003)
Botulinum toxin type a for facial rejuvenation: treatment evolution and patient satisfaction (2010)
Upper face rejuvenation using botulinum toxin and hyaluronic acid fillers (2013)
Botulinum toxin A in the mid and lower face and neck (2004)
Aesthetic indications for botulinum toxin (1994)
Faces First Cosmetic Surgery (n.d.)
Neurotoxin injection technique to the medial brow depressors (2020)
Advanced Techniques for the Use of Neurotoxins in Non-Surgical Facial Rejuvenation (2020)
Injectable Neurotoxins (n.d.)
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