Botulinum Toxin in Oculoplastics - Cosmetic Implications

Introduction:

Botulinum neurotoxin is produced by the gram-positive, spore-forming bacteria Clostridium botulinum, which causes human botulism. It was first used by Scott et al. in 1973 to treat strabismus. It was first used on humans in 1980. The Food and Drug Administration (FDA) approved botulinum neurotoxin type A for treating blepharospasm, strabismus, hemifacial spasm, and the area around the glabella (the part of the forehead between the eyebrows) for cosmetic purposes. Individuals treated with botulinum neurotoxin for blepharospasm (uncontrolled twitching of the eyelids) showed a reduction in the wrinkles of the face.

What Is the Mechanism of Action of Botulinum Toxin?

The mechanism of action of botulinum toxin in oculoplastics is based on inhibiting the release of acetylcholine (neurotransmitter) at the neuromuscular junction, resulting in paralysis of the muscular tissues. The toxin is made of heavy and light chain molecules. The heavy chain binds to the receptors of the motor nerves, which in turn imbibe the botulinum toxin through endocytosis - a process by which certain substances are brought within the cells.

The toxin comes into contact with an acidic environment inside the endosomes. This leads to the detachment of the light chain from the toxin, which eventually passes into the cells of the motor neuron. The light chain within the motor neuron cells helps to split the protein responsible for releasing acetylcholine. The effect of botulinum toxin is at its peak around the 14th day and lasts for around three months.

How Is Botulinum Toxin Administered?

Botulinum toxin is administered with the help of a one milliliter 30-gauge syringe. 200 units/4 mL or 100 units/2 mL is the suggested dilution, with a final concentration of 5 units per 0.1 milliliter. The area to be injected should be cleaned with the help of an alcohol-free antiseptic solution. Topical anesthetic creams containing a combination of Prilocaine and Lidocaine are used to numb the area and reduce the pain sensation. During the process, the skin is stretched to see the superficial blood vessels, which are supposed to be avoided while injecting the toxin.

In Which Regions Is Botulinum Toxin Administered?

• Forehead and Glabellar Wrinkles:

The wrinkles on the forehead are caused by the frontal muscles. As these frontal muscles pull the other muscles, horizontal wrinkles appear on the forehead. Deep wrinkles are formed when the medial fibers of the frontal muscles are pulled. Intramuscular botulinum injections of 10 to 15 units are administered in six to seven places. The glabellar wrinkles are caused by two muscles, the procerus and the corrugator superciliaris muscles. The procerus muscles cause the horizontal lines, and the corrugator superciliaris muscle causes the verticle wrinkles. Around five injections are administered in a V-shape to the glabellar area with a dose of 20 units. The dose of botulinum toxin for men is relatively higher than that for women because of thicker muscles.

• Eyebrow Repositioning:

The shape of the eyebrows differs from person to person. With aging, the lateral part of the eyebrow descends, whereas the center part droops down due to gravity or rises due to the upward pull of the frontalis muscle. Botulinum injections given under the lateral part of the eyebrow can make the orbicularis oculi muscle weak, thus lifting a part of the eyebrow. 10 to 15 units of botulinum toxin are equally divided among the three sites of the brow. The process can cause around a five-mm rise in the eyebrows. The diffusion of the toxin to the surrounding areas can lead to diplopia (double vision), ptosis (drooping of the eyelid), and an excessive rise of the eyebrow.

• Periorbital Wrinkles:

Periorbital wrinkles, also known as crow's feet, result from movements of the orbicularis oculi muscle. A 12-unit equally divided dose of three injections of botulinum toxin is effective. While administering the injections, care must be taken to avoid the zygomaticus major and levator labii superioris muscles, as this may lead to lip ptosis.

• Strabismus:

Strabismus, also known as the cross-eye, is a condition in which the eyes do not simultaneously see in the same place. Botulinum toxin was first used in humans by Alan Scott to treat strabismus. The aim is to decrease the deviation caused by the weakening of the antagonist's muscle. Botulinum toxin is suitable for individuals for whom general anesthesia is not recommended or for paralytic strabismus. The botulinum injection dose is around one to three units per muscle.

What Are the Complications of Botulinum Injections in Oculoplastics?

The effects of botulinum toxin are self-limiting; however, the systemic distribution of the toxin to adjacent structures may give rise to some complications:

When administered in the ophthalmic area, the complications include the following:

• Bruising.

• Swelling.

• Asymmetry.

• Headache.

• Ptosis can occur depending on the injection site and dosage.

• Diplopia is caused due to the involvement of the extraocular muscles.

• Anaphylactic reactions type one.

• Weakness of the orbicularis oculi muscles leads to poor lid closure or paralytic ectropion.

• Individuals with complications should be closely monitored to prevent exposure to the ocular surface. The complications resolve after 10 to 15 weeks of administration. With time, the individual may also develop antibodies against the toxin, thus making the medication ineffective.

The development of these antibodies depends on the following:

• The dose of the toxin used.

• Frequency of the administration.

• The amount of protein present per unit of the toxin.

The use of botulinum toxin is restricted to pregnant and lactating women. Individuals with a history of neuromuscular disorders should not be given the toxin. Aminoglycoside antibiotics can react with neuromuscular transmission, thus increasing the effects of the toxin. The complications of the injection site may include pain, redness, ptosis, muscle weakness, headache, ecchymosis, and hyperesthesia. Other side effects may include ectropion, lower eyelid drooping, diplopia, and an asymmetric smile.

What Does Botulism Mean?

Botulism is a rare, serious disorder caused by a toxin secreted by Clostridium botulinum that attacks the body's nerves. Botulism manifests as the weakness of the muscle that controls the eyes, mouth, face, and throat. The symptoms would be:

• Difficulty in swallowing.

• Double vision.

• Drooping of the eyelids.

• Slurred speech.

• Difficulty in Breathing.

• Vomiting.

• Nausea.

• Stomach ache.

The symptoms vary from person to person. The common symptom is the paralysis of the muscle in relation to the affected site.

There are five kinds of Botulism and they are

• Infant Botulism: Bacteria grow in the Infant’s intestines and cause illness.

• Wound Botulism: Bacteria in the wound can cause botulism.

• Foodborne Botulism: Occurs when food contaminated with the toxin is taken.

• Iatrogenic Botulism: It occurs when botulinum toxin is taken for cosmetology like botulinum injections.

• Adult Intestinal Toxemia: It is a rare kind where the toxin gets into the adult intestines and causes diseases.

Conclusion:

Botulinum neurotoxin is one of the most poisonous substances. It could paralyze the striated muscles. This muscle-paralyzing feature of the toxin is beneficial for many pathological and cosmetic conditions. Botulinum neurotoxin injections for certain cosmetic procedures are commonly administered worldwide. It has been found to reduce the signs of aging around the eyes and face. Apart from its use in oculoplastics, it has been used in ophthalmology for treating eyelid and lacrimal system disorders.