One side effect, weakness in the limb, was very common in the patients who received Botox -- 42 percent reported it, compared with 6 percent among those who received the placebo. However, the weakness was mild to moderate in the patients and went away within two weeks.
It's not clear how the drug relieves tremors, but it may have something to do with changing the way muscles, nerves and the brain interact, van der Walt said.
The patients received an average of 83 international units of Botox, about three to four times the amount used for wrinkles, although less than the typical amount that migraine patients get. The injections are needed from two to four times a year and cost the equivalent of about $500 to $1,000 in Australia, van der Walt said.
She recommended that "patients who are interested in exploring Botox treatment for their tremor [should] make sure that they are referred to a movement disorder specialist with both an interest in tremor and expertise in complex Botox injections."
Commenting on the study, Dr. Thomas Guttuso Jr., an assistant professor of neurology at the University at Buffalo in New York, said Botox currently is usually reserved for patients with severe, continuing tremor "that is markedly interfering with certain activities of daily living."
Guttuso added, "My own experience with these patients is that Botox can be effective when the tremor occurs more at the shoulders and elbows but not as effective when the tremor occurs more at the wrists and fingers."
He added that it's not clear if Botox leads to "meaningful" differences in the lives of patients, and future research will need to examine that issue.
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