Injections into the overactive muscle are done with a small needle, with one to three injections per muscle. Discomfort at the site of injections is usually temporary, and a local anesthetic may be used to minimize any discomfort associated with the injection. Botulinum toxin type-A was developed as a therapeutic agent for this disorder along with blepharospasm, hemifacial spasm, and other disorders characterized by inappropriate muscle spasms. It has been widely used as an effective treatment for dystonia, reducing the spasms or sustained muscle contractions in the eyelids, neck, vocal cords, hands, and limbs. Effects of the treatment generally starts to show within five to ten days with benefits lasting three to four months after which a gradual decline occurs until the injection needs to be repeated.
Side effects are usually transient and mild to moderate in nature.
Some people notice temporary weakness of muscles or discomfort at the injection site. Symptoms may vary throughout the course of the condition, and so the degree of relief and duration of effect varies from person to person. Since the effects of botulinum toxin usually last only a few months, permanent impairment would be highly unlikely and no such complications have been reported. Acceptable safety in long-term treatment has been well established. There are a number of possible reasons for this lack of response.