Movement Disorders

Botulimum Toxin Injections for Treatment of Movement Disorders

Botulinum toxin, a toxic protein produced by the bacterium Clostridium botulinum, causes botulism, a deadly form of food poisoning. But in tiny quantities, the toxin acts as a muscle-relaxing agent by blocking the release of acetylcholine in the nerve endings. Acetylcholine transmits electrical messages between the brain and the muscles. When the botulinum toxin blocks its release, the messages are not delivered. As a result, muscle contractions and associated pain are reduced.

Minute amounts of the toxin are injected directly into the muscle responsible for the spasms. The toxin weakens the muscle, but does not paralyze it, and allows the affected area to resume a more normal position. Pain from prolonged muscle contractions is eased. The treatments can be used in the eyelid to treat blepharospams, and in muscles elsewhere in the body, such as the arm or leg.

Botulinum toxin types A and B are available and effective in treating focal or segmental dystonias. Botulinum toxin has seven forms (serotypes): A, B, C, D, E, F, and G.

Botulinum toxin injections are not a cure, but they usually ease symptoms in the injected muscle in seven to 10 days. Patients usually receive maximum benefit one to two weeks after the injections. The effects can last several months, and the treatments can be repeated, often indefinitely.

A very fine needle is used for the one to three injections that are normally given per muscle. Discomfort from the injections, if any, is usually minor and temporary.

Because symptoms vary during the course of dystonia, the treatment's effectiveness and duration vary from patient to patient. Subsequent injections may produce results that are less dramatic than the first, and doses may have to be adjusted. Identifying and injecting the affected muscle is not always easy.

In rare cases, a patient can develop antibodies to the botulinum toxin proteins, rendering the treatment ineffective.

Botulinum toxin treatments should not be used by pregnant or nursing women or by people taking certain medications. Side effects to the treatment include a temporary muscle weakness and discomfort at the injection site.