Botulinum Toxin in Facial Rejuvenation E-Book

Kate Coleman

• Éditeur: Elsevier
• Année: 2019
• ISBN:
  9780702077876
• Édition: 2
• Sujet: Medizin
• Sous-sujet: Plastische Chirurgie & Schönheitsmedizin

Now thoroughly revised to reflect state-of-the-art advances in the field, Botulinum Toxin in Facial Rejuvenation, 2nd Edition, covers the entire range of the use of botulinum toxin for cosmetic purposes. Dr. Kate Coleman offers practical guidance for safe handling, selection and assessment of patients, potential complications and pitfalls, and aesthetic techniques, as well as comparative modalities and long-term management. This is an ideal resource for anyone who offers this sought-after procedure, including cosmetic surgeons, oculoplastic surgeons, dermatologists, physician's assistants, and registered nurses.

• Features new, unique coverage of long-term management, picturing the same original patients 15 years later, as well as observations on how treatments should be adjusted as the patient gets older in order to respond to natural changes in bone density and underlying support structures.
• Presents new knowledge on neuromodulation and how treatment can be used to 'retrain' expressions to provide fewer frowns lines and better facial symmetry.
• Offers comparative information on other modalities such as laser and hyaluronic acid, as well as potential risk factors, so you can choose the best procedure for each patient.
• Discusses the various forms of botulinum toxin currently available on the market, with an emphasis on Botox, Xeomin, and Dysport.
• Uses full-color clinical photos of pre-, peri-, and post-operative results to illustrate nuances of techniques as well as the effectiveness of botulinum toxin on wrinkles and scars for the major facial areas.
• Provides current guidelines on treatment methods and best practices for reconstitution and storage.
• Discusses which patients may be at risk for adverse effects ?or "worsening results"?and offers suitable alternatives.

Chapter 1

Historical background

Abstract

Botulinum toxin comes from Clostridium botulinum bacteria. Type B was discovered in 1910 and type A in the 1920s. It was researched for chemical warfare, and in 1982 Dr. Alan Scott published results on its use around the eye. Botox is produced by Allergan from the original strains explored by Dr. Scott. Dysport evolved from the Porton Down laboratories, United Kingdom, when bought by Ipsen Pharmaceuticals. The author began using Dysport and Botox in the late 1980s to eliminate hyperactive wrinkles on the faces of patients with facial paralysis and hemifacial spasm.

Keywords

Botox; Dysport; Wrinkles; Botulinum toxin

The Clostridium family of bacteria, common to most environments, produces spores that, on germination, release some of the deadliest toxins known to mankind. Clostridium Perfringens contaminates wounds and caused the infamous gas gangrene of World War 1; Clostridium botulinum produces botulinum toxin (BTX)—a powerful neurotoxin.

Clostridium botulinum was first identified in 1897, in Belgium, by Professor Emile van Ermengenen, who was investigating fatal cases of food poisoning following the consumption of macerated ham. It was named after the disease it causes, botulism, a lethal form of food poisoning originally associated with sausage meat (botulus is Latin for sausage). In the same year, an antiserum for botulism was made.

There are seven known serotypes of BTX (A, B, C, D, E, F and G). Serotypes A, B and E cause the classic foodborne disease with a flaccid paralysis of motor and autonomic nerves. Type B was first discovered in 1910, and the isolation of type A began in the 1920s. During the Second World War, research continued into this potent neurotoxin as a possible agent (‘agent X’) for biological warfare. Most of this work was carried out at the chemical warfare laboratories of Fort Detrick, Maryland, and Porton Down in the United Kingdom. Porton Chemicals was bought by Ipsen Pharmaceuticals in 1989 and is the source of Dysport.

Dr Alan Scott, an ophthalmologist from the Smith-Kettlewell Eye Research Foundation, became interested in substances that caused transient muscular paralysis. He acquired BTX type A from Fort Detrick and performed the first clinical tests on humans in 1978. His results in the treatment of strabismus (an abnormal contraction of the extraocular eye muscles) were published in 1982 and led to the extensive use of BTX type A by ophthalmologists in the treatment of blepharospasm (an abnormal twitching and contraction of the muscles around the eye), hemifacial spasm and cervical dystonia.

By the late 1980s, the author, an oculofacial and ophthalmic surgeon in Ireland, as well as colleagues in Canada and the United Kingdom, were each exploring different doses and methods for using BTX. The author worked on patients with facial asymmetry, especially Bell palsy, to calculate the doses required to ‘balance’ the innervation of the whole face.

Thereafter the story is well known. With good medical training and the correct selection of patients, BTX can be given easily, safely and repeatedly. There have been relatively few reported side effects despite ever-increasing demand in increasingly large doses, in particular for large muscle dystonia and spasm.

Thanks to Dr Scott, many lives have been enhanced and many more made bearable by this deadliest of poisons and astonishingly precise drug.

Chapter 2

Botulinum toxin: Mode of action and serotypes

Dr. Kate Coleman, BSc PhD FRCS FRCOphth

Abstract

Botulinum toxin comprises a light and a heavy chain protein molecule. The heavy chain attaches the molecule to the nerve membrane, allowing the light chain to reach the site of action at the protein complex in the nerve ending. The toxin inhibits the release of acetylcholine at the neuromuscular junction and can inhibit contraction for 12 weeks before new nerve endings bud and restore function. The autonomic cholinergic receptors are also blocked, for up to 12 months. Central action can result from anterograde and retrograde axonal transport with secondary reduction of elements of the basal ganglia. Antinociceptive effects are due to blockades of pain and inflammatory mediator release. The different serotypes act on different elements of the vesicle-associated membrane protein/synaptosomal-associated protein-25/syntaxin protein complex. The development of antibodies to the protein complex is reported in 2% with serotype A (BOTOX) as opposed to 20% to 40% with serotype B (Myobloc).

Keywords

BOTOX; Dysport; neurotoxin; antinociceptive; serotype

A working knowledge of the pharmacology of botulinum toxin (BTX) is essential to understand the contraindications and complications of treatment with it.

Botulinum neurotoxins are metalloprotease polypeptides, comprising a protein molecule (150 Kd), which can be cleaved enzymatically into a heavy (H) (100 Kd) and a light (L) (50 Kd) chain (Fig. 2.1). These chains are normally held together by a disulphide bond, which is heat labile. Disruption of this bond inactivates the neurotoxin. This explains why BTX must be stored at the correct temperature and reconstituted carefully, preserving the integrity of the two-chained molecule. Prior to reconstitution, characteristics of Incobotulinum toxin A (Xeomin) reflect the lack of a complexing protein with the neurotoxin, allowing lpng term stability and reduced immunogenicity.

Fig. 2.1Diagram of botulinum toxin molecule showing heavy and light chains. (From Aoki R. The development of Botox—its history and pharmacology. Pain Digest. 1998;8:337–341. With permission from Springer-Verlag.)

BTX induces paralysis by blocking the release of acetylcholine at the skeletal alpha motor neurone neuromuscular junction, thereby inhibiting the transmission of nerve impulses across the synaptic junction to the motor end plate.

User Tip

Always consider possible central, as well as obvious peripheral, changes to the injected muscle following treatment (neuromodulation).

Muscular contraction: Normal cholinergic transmission (fig. 2.2)

Voluntary muscle contraction is a response to stimulation by action potentials passing along a nerve to the muscle. Once these action potentials reach a synapse at the neuromuscular junction, they stimulate an influx of calcium into the cytoplasm of the nerve ending. This increase in calcium concentration allows acetylcholine to fuse with the membrane, using a protein complex, before crossing the synapse and fusing with nicotinic receptors on the muscle fibre. The protein complex consists of three types of protein: vesicle-associated membrane protein (VAMP; synaptobrevin), synaptosomal-associated protein (SNAP)-25 and syntaxin.

Fig. 2.2Normal cholinergic transmission: (1) A signal passes down the cholinergic nerve, causing calcium to pass through the depolarising presynaptic membrane. (2) The calcium then triggers the binding of the acetylcholine molecule to a protein membrane complex. (3) The protein membrane complex allows the acetylcholine to pass into the synaptic cleft. (4) The acetylcholine travels across the synapse to a nicotinic receptor on the muscle, where it stimulates contraction before disintegrating into acetate and choline (5). VAMP, Vesicle-associated membrane protein.

Mode of action of botulinum toxin (fig. 2.3)

Acetylcholine depends on a protein complex for its release from the nerve ending into the synapse. BTX, using a specific enzyme in the L-chain, interacts with one component of the protein complex of the nerve terminal, thereby inhibiting the discharge of the acetylcholine. The protein attacked is specific to the different serotypes of BTX; for example BTX-A blocks SNAP-25, whereas BTX-B blocks VAMP. BTX-B acts on a different cytoplasmic protein complex. The secretion of acetylcholine is disrupted when the L-chain of the BTX-B molecule cleaves a protein called synaptobrevin, also known as VAMP. Clinical trials have shown BTX-B to be effective for the treatment of patients with cervical dystonia, including those resistant to BTX-A.

Fig. 2.3Action of botulinum toxin (BTX) at the neuromuscular junction: (1) The heavy chain of the BTX binds to synaptogamin on the presynaptic membrane. (2) The heavy chain/synaptogamin complex enables the BTX light chain to enter the cell. (3) The light chain attacks the membrane complex and disables it so that NO ACETYLCHOLINE (AcH) BINDS. (4) BTX-A attacks the SNAP-25 protein of the membrane protein complex, and BTX-B attacks VAMP (synaptobrevin). (5) There is no releas...