(see information on Hemifacial Spasm)
Botox is a purified preparation of botulinum toxin (distributed and licenced by Allergan, Inc.) Excessive amounts of this substance is known to cause food poisoning and weakness in humans. However, the amount that is injected into the muscles of the face to treat hemifacial spasm is 100 times smaller than the dose that causes poisoning. No patient has had poisoning from this drug after being treated for eyelids spasms.
The treatment involves injecting small amounts of Botox under the skin into the overacting muscles in the eyelids, eyebrows, and, if necessary, also into other areas, including the muscles around the mouth, nose, cheek and neck. There can be mild swelling around the injected sites which goes away within a few hours. After the muscles are injected they become weak for an average of 3 to 4 months. After this interval the muscle strength returns to almost normal and the spasms usually come back. However, the patient’s overall condition is usually better than it was before the treatment. The success rate for treating eyelid spasms with Botox is over 90 %. However, it is not a cure: In most cases, treatments have to be repeated on an indefinite basis, at average intervals of 3 to 4 months.
While no poisoning has ever occurred when using Botox for facial spasms, the drug can cause side effects around the eye due to spreading into structures around the eye or due to excessive weakness of the eyelid muscles . These effects are temporary in almost all cases, resolving within 4 to 8 weeks.