Botulinum toxin is a neurological poison which weakens muscle by interfering with nerve impulses which normally initiate muscle contraction. Prepared as a purified protein, it is now used as a medicine to treat conditions which result from excessive, involuntary contraction of muscles.
It was initially approved by the FDA in 1989 for the treatment of adult strabismus (crossed eyes), blepharospasm (uncontrollable blinking) and hemifacial spasm. It is now also considered the treatment of choice for other forms of focal dystonia such as cervical dystonia (spasmodic torticollis), oromandibular dystonia (jaw) and laryngeal dystonia (spasmodic dysphonia). There are now three brands of botulinum toxin type A (Botox, Dysport, Xeomin) and one brand of botulinum toxin type B (Myobloc) FDA approved for the treatment of dystonia.
Albany Medical Center’s movement disorder neurologists at the Parkinson’s Disease and Movement Disorders Center are subspecialty trained in the use of botulinum toxin and have extensive experience in the treatment of dystonia with this technique. Other modalities, such as medications and deep brain stimulation surgery, are also used to treat dystonia.
Botulinum toxin is injected into the affected muscles with a very small needle. The size of the muscle and force of contraction generally determines the dose used and number of injection sites in each muscle. Potential side effects include excessive weakness of the muscles injected and flu symptoms. A small percentage of patients will develop antibodies to the toxin which are not dangerous, but will render the treatments ineffective. In experienced hands, excellent results can be achieved by choosing the proper muscles to inject and the appropriate dose. This helps to ensure that side effects are avoided and the dystonic spasms are relieved without losing voluntary control over the muscles injected.
The treatment generally begins to relieve symptoms within a few days and the affect gradually increases over the next 3-4 weeks. The benefits usually last around 3 months then gradually wear off at which time the treatment may be repeated. There are no known serious long-term adverse effects of the treatments. However, the smallest effective dose is used and the interval between treatments extended as far as possible to help avoid side effects and the development of immunity through the formation of neutralizing antibodies.
The neurologists at the movement disorders center have been active researchers into the nature of dystonia and its treatment. They have participated in controlled clinical trials designed to evaluate the effectiveness of Botox, Dysport and Myobloc in cervical dystonia and Xeomin in blepharospasm. They have also helped to develop reliable instruments to measure the severity of cervical dystonia.