Best known as a cosmetic treatment used to lessen the appearance of wrinkles, botulinum toxin type A has long been used to relax muscles and treat uncontrolled muscle contractions. Current research is showing, however, that botulinum toxin type A injections may significantly reduce chronic pain when used in combination with physical therapy.

"[Botulinum toxin type A] blocks the release of neurotransmitters," explains Donald Tanenbaum, DDS, who maintains a private practice with offices on Long Island and in New York City. "The main neurotransmitter that is blocked is acetylcholine, which is essentially responsible for initiating the events that become a contraction." If the main neurotransmitter is absent from a muscular area, that muscle does not have the capacity to contract. "The administration of [botulinum toxin type A] is designed to partly inhibit the local musculature from contracting, incapacitating the muscles," he adds.

Tanenbaum uses botulinum toxin type A on patients who have sustained muscle contracture that results in chronic myofascial pain. They are usually responsive to short-term therapy like medications or trigger point injections with anesthetics such as lidocaine. "When muscles are in a sustained contracture position, they become fatigued and can't relax. Once you reduce the contraction, you get fresh blood flowing, fresh oxygen, clean out the bad chemical by-products, and the muscle recovers," he notes. As the muscle tightens up over the next couple of weeks or months, the problem resurfaces. Tanenbaum is comfortable using botulinum toxin type A in this type of situation. "Though I'm just buying you more time," he says. "Maybe we can break up a pain cycle for a period of time and make the next 3 or 4 months comfortable with the knowledge you may have to repeat this. It's not going to cure anything." He has been using it on his patients for about 3 or 4 years.

Some of Tanenbaum's patients have bad habits like teeth clenching or grinding, and despite using bite guards and habit breaking strategies, they continue to have tooth contact and contracture. Tanenbaum realizes that the muscular power is tremendous and has used botulinum toxin type A to relax their masseter and temporalis muscles. These muscles move the mandible against the upper jaw and enable crushing of relatively hard food. In humans, the mandible is connected with the temporomandibular joint (TMJ) that permits forward-backward and side-to-side movement. "Botulinum toxin type A makes it more difficult for those muscles to create injury. Certainly this should not be first-line treatment for TMJ dysfunction," Tanenbaum stresses. "This is something that can be utilized if traditional care is not working, or if it is working and just doesn't last."

OTHER USES

"I use [botulinum toxin type A] for migraine management, neck pain, and back pain," says Lynne Columbus, DO, an anesthesiologist specializing in pain management at Gulf Coast Pain Management in Palm Harbor, Fla. "It's also used for spasticity; it actually paralyzes the muscle," she adds. The procedure includes injecting [it] into the muscle through the skin. The site may be determined by using a small electric stimulator (EMG machine), which allows the physician to correctly locate the muscle to inject. A small electric current may be applied onto the surface of the skin or just beneath the surface with a small, sterilized needle.

With migraine management, for example, a major symptom of the pain is muscle contraction. "[It] inhibits that muscle contraction, which helps decrease the pain," Columbus says. "It not only does that as far as pain management is concerned, but it is believed that it decreases the release of painful chemicals like CGRP (calcitonin gene-related peptide). Because it decreases the release of those painful chemicals, it helps improve symptoms like allodynia," she says. Allodynia is the hypersensitivity of neurons to normally innocuous stimuli on the skin such as a touch or the temperature that often accompany a migraine. Typically, Columbus injects the patient and then has the patient pursue physical or manual (massage) therapy. "That seems to get the best results," she says. It can last 3 to 6 months, she says. On the average, it lasts 4 months.

BENEFITS AND RISKS

Potential benefits of this treatment include the reduction in painful spasms; increased ability to range a joint such as the ankle, knee, or arm; increased speed of walking and other functional abilities; and for certain physical therapies to be performed more easily such as splinting and casting. Using the serum to relax the muscles before therapy maximizes the potential for rehab and repair of damaged muscle tissue, strengthens weakened muscles caused by spasms, and relieves pain.

Botulinum toxin type A has the advantage of being a potent neuromuscular blocking agent with good selectivity and duration of action, with few side effects. "There's a risk of a reaction to the medication—an allergic reaction—but that is very rare," says Columbus. "I've never had that happen in my practice." Common side effects include muscle weakness that may affect function of the limb treated and local bruising. "There is a risk of side effects such as flu-like symptoms or pain at the injection site," she adds.

Rarer side effects have been reported but are not necessarily a result of using it. Nausea, muscle soreness, headaches, lightheadedness, fever, chills, hypertension, weakness, difficulty breathing, diarrhea, and abdominal pain have been noted.

"If it was administered in an inappropriate dose, it would prevent the muscles that move your diaphragm from contracting and you wouldn't be able to breathe," adds Tanenbaum. "Or it could stop your heart from beating because your heart is a muscle as well." Tanenbaum and his colleagues are currently drafting guidelines for the use of the serum in facial pain disorders.

Botulinum toxin type A is approved by the FDA for treatment of blepharospasm and hemifacial spasm but has not been approved in treating dystonias, spasticity, or muscle pain. The American Academy of Neurology has deemed this drug safe and effective in the treatment of oromandibular, cervical, spasmodic, and focal dystonia. The NIH also has issued a statement that this drug is effective and safe in treating these disorders.

New studies imply that the release of pain-inducing neurotransmitters is suppressed in sensory nerve endings by the serum. "There appears to be developing evidence that there is independent action in [botulinum toxin type A] on peripheral nerve receptors and there's a thought that it actually blocks the transmission of certain neurotransmitters that are involved in pain," Tanenbaum says. "If you can inhibit the nerve from becoming hyperexcited in skin and muscles, you'll have a major impact on the brain's ability to receive signals that say, ‘This hurts' or to experience pain."

Nina Silberstein is a contributing writer for  Rehab Management. For more information, contact http://www.rehabpub.com/issues/articles/2007-01_06.asp