Botulinum toxin
Botulinum toxin injections have been used to induce localized, partial paralysis. Among most sufferers, botulinum toxin injection is the preferred treatment method. Injections are generally administered every three months, with variations based on patient response and usually give almost immediate relief (though for some it may take more than a week) of symptoms from the muscle spasms. Most patients can resume a relatively normal life with regular botulinum toxin treatments. A minority of sufferers develop minimal or no result from botulinum toxin injections and have to find other treatments. For some, botulinum toxin diminishes in its effectiveness after many years of use. An observed side effect in a minority of patients is "ptosis" or eyelid droop. Attempts to inject in locations that minimize ptosis can result in diminished ability to control spasms. A recent Cochrane systematic review showed that a single treatment session (where both eyelids were injected with BtA multiple times) alleviated the symptoms of blepharospasm, disability, and number of involuntary movements.