PATHOLOGY PERSPECTIVES
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2011. www.drugs.com/pro/botox.html. "Botox & Myobloc: What Are They
RESOURCES "Botox." Drugs.com. Accessed March
& Why Has the FDA Issued A Warning." FreeAdvice 2011. Accessed March 2011. http://injury-law.freeadvice.com/drug- toxic_chemicals/botox-myobloc-what- are-they-why-fda-issued-warning.htm. Brashear, A. et al. "Intramuscular
Injection of Botulinum Toxin for the Treatment of Wrist and Finger Spasticity After a Stroke." New England Journal of Medicine 347 (August 8, 2002): 395–400. Accessed March 2011. www.nejm.org/doi/ full/10.1056/NEJMoa011892#t=articleTop. Davis, C. "Botulism." MedicineNet,
Inc. Accessed March 2011. www. medicinenet.com/script/main/ art.asp?articlekey=10363. Harden, R. et al. "Botulinum
bacteria, which have several subtypes, secrete a substance that seeps into motor neurons at the motor end plate, and it blocks the secretion of acetylcholine altogether, leading to flaccid paralysis of the affected cells. The action of this toxin is permanent. The motor axon branches that are exposed will never secrete acetylcholine again, and the affected muscle cells are effectively out of commission until the neuron regenerates new terminating axons—a process that can take weeks or months. A botulism antitoxin has been
Toxin A in the Treatment of Chronic Tension-Type Headache With Cervical Myofascial Trigger Points: A Randomized, Double-Blind, Placebo-Controlled Pilot Study." Accessed March 2011. www. medscape.com/viewarticle/703592. "Medication Guide: Botox." Allergan,
Inc. Accessed March 2011. www.allergan. com/assets/pdf/botox_med_guide.pdf.
developed and can be used in cases where accidental botulism toxin exposure occurs. This can stop the progression of nerve damage, but not reverse it—whatever muscle power is lost will not be regained until the affected neurons regenerate their axon terminals. Advances in the understanding of this pathogen and its toxin, along with better attention to careful hygiene in food storage, means that botulism poisoning has become rare in this country, but about 100 cases of accidental poisoning are still reported annually.
BOTULISM TO THE RESCUE The neurotoxin that causes the paralysis associated with botulism was first isolated in 1944. While it has been considered as a possible biological weapon, other uses have prevailed. A diluted and purified version of it was first used therapeutically in 1980 for strabismus—a condition involving the muscles that control eye movement. In 1989, the US Food and Drug Administration (FDA) approved the use of botulinum toxin for several muscle problems of the face and neck. In 2002, the FDA approved the use of botulinum toxin for some other conditions, as well as for cosmetic uses—it can temporarily paralyze the muscles of facial expression that cause wrinkles. From that time, the industry grew fast,
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and some subtypes of the laboratory- prepared material have now become available. The most common trade names are Botox, Botox Therapeutic, Dysport, and Myobloc. Some preparations of botulism toxin have slightly different effects for different conditions, and the dosing guidelines are unique to each brand—they are not interchangeable. Consequently, in 2009, the FDA issued "black box" label warnings so that professionals would use these products with great care.
WHAT IS IT USED FOR? Botulinum toxin is used cosmetically to address glabellar lines (those are formed by forehead muscles that pull the eyebrows together in a frown), and to reduce tone in other facial muscles, specifically the corrugator and procerus muscles. The net result is a face with a reduced appearance of wrinkles, brought on by induced flaccid paralysis of the key muscles. It typically takes three to six months for the affected neurons to grow new axon terminals, at which time control of the muscles is restored. In addition, the toxin is approved for
use to treat the following conditions. • Strabismus. This condition involves asymmetrical tone in the muscles that move the eyeballs. The result is sometimes called "lazy eye" or "crossed eyes," and the pupils are not parallel. Botulinum toxin can equalize the muscle tone between the eyes.
• Blepharospasm. This is a condition in which the orbicularis oculi muscle involuntarily contracts. It may be a part of several different types of dystonia, and it can lead to functional blindness, even though the eyes themselves are not affected.
• Hemifacial spasm. This unilateral involuntary contraction of the muscles of the face can be related to a cranial nerve irritation, a tumor, or unknown factors. Botulinum toxin prevents the contractions.
