Given botulinum toxin's ability to interfere with neuromuscular signal transmittance, scientists and doctors have long since tried to harness this chemical property for medical application. Botulinum toxin was first examined by military scientists and considered for use in chemical warfare (Gross). Japanese scientists experimented with botulism toxin shortly before World War II during the occupation of Manchuria by feeding cultures of C. Botulinum to Chinese prisoners (Arnon 1060). The United States likewise produced it as part of its bioweapons program from World War II until 1970 (Arnon 1060). However, since then man has found many more beneficial clinical applications in the treatment of neurological disorders. More recently doctors have used it cosmetically to treat wrinkle-causing facial muscles.
3.1 Clinical Uses
Because of its unique neurological effects, botulinum toxin, specifically toxin type A (Botox or BTX-A), has been used since the 1970s to treat many different disorders characterized by excessive or harmful muscle contraction (Brin 280). One of its first popular applications was to treat various forms of dystonia. Dystonia is a neurological disorder characterized by involuntary movements and prolonged, rapid and repetitive muscle contraction (Brin 288). It usually results in twisting body movements, tremors or abnormal posture. Botox treats focal dystonia, or dystonia limited to a specific body part, by partially paralyzing the local muscle.
Since Botox is easily injectable, it can be used on virtually any muscle group, creating many potential applications (Brin 287). Botox has been used to treat general spasticity resulting from stroke, multiple sclerosis or cerebral palsy (Hallet 118). In the early 1980s Botox was found useful in treating children with strabismus, a condition where the visual axes of the eyes are not parallel, causing possible blindness (Rohrich 177S). With this treatment, Botox is injected into the muscles around the eye, partially paralyzing them. Botox has even been found useful in the treatment of hyperhidrosis, or excessive sweating (Heckman 488). It works in this application by blocking acetylcholine release from the neuromuscular junction that stimulates sweat glands.
Currently, Botox is being explored as a tool to alleviate pain. Researchers were prompted to consider Botox for pain relief when many dystonia patients reported that the pain relief resultant from Botox injections exceeded any derived motor benefit (Brin 292). Since then, doctors have found Botox injections extremely effective in combating and preventing migraine and tension headaches (Silberstein 448). While the mechanism is unclear, Botox may work against headaches by interfering with any muscular trigger that could provoke a migraine (Brin 292). It is also possible that Botox interferes with pain pathways through some as yet unknown effect on the sensory system (Silberstein 449).
3.2 Cosmetic Uses
While it is clear that the clinical applications of Botox are extensive, its cosmetic uses garner all the attention. In a way this is tragic because it was through clinical use that Botox's cosmetic benefits were discovered. In 1987, Dr. Jean Carruthers, in using Botox injections to treat blepharospasm, a form of dystonia where the eye uncontrollably blinks, discovered that the Botox also smoothed her patient's facial lines. After she relayed this information to her dermatologist husband, Dr. Alastair Carruthers, cosmetic Botox use was born. Dr. Carruthers performed the first successful cosmetic Botox injection on his secretary to smooth her brow lines in 1987 (Milne 32). Since then, Botox has been recognized as a useful weapon against undesired facial lines, or so called hyperfunctional lines.
Facial lines can be separated into two categories, dynamic and static. Figure 2 shows an example of dynamic and static lines of the glabellar region, or area between the eyes. Dynamic facial lines form when the underlying muscle contracts and are generally useful in indicating an emotion, such as anger or fear. Whereas glabellar lines may express anger when formed, lines around the mouth that form during a smile help express happiness. Lines on the forehead that form while elevating the brow help express surprise (Finn 451). Static facial lines may appear through frequent formation of dynamic facial lines and involuntarily develop without muscle contraction. When dynamic and static lines occur "more frequently or more intensely than desired for expression," the lines are said to be hyperfunctional (Finn 451).
Botox is used to minimize or eliminate such hyperfunctional lines. Its first target was the glabellar region. It was then found useful in removing the hyperfunctional lines of the forehead and lateral orbit, more commonly called crow's feet (Blitzer 304). Botox has also been found effective in treating undesirable bands of the neck and hyperfunctional lines near the mouth (Sposito 75S).
The mechanism of Botox action is the same when used in cosmetic applications as it is when used clinically or as a bioweapon. Facial muscles, like all other muscles, require acetylcholine in order to contract, even when contracting involuntarily. The difference between the applications is that as a bioweapon, botulism toxin is either inhaled or ingested in large amounts, affecting muscles throughout the entire body. Clinically, Botox is injected locally into one muscle in an amount proportional to the size of the muscle, but still smaller than the amount used to kill. Because the muscles of the face are so much smaller and more delicate, Botox is injected in even smaller doses.
