The study will follow a cross-over design to maximize statistical power and decrease biases inherent to small samples as patients will become their own controls. After a baseline assessment, patients will be randomized to receive either botulinum toxin or an equal amount and distribution of normal saline (placebo). Patients will undergo reassessment of function at one and four weeks after the initial and second session of injections. The second procedure will occur, using the opposite treatment arm (Botox® or saline placebo), three months after the first injection session. Doses of levodopa, dopaminergic agonists, and antidyskinetic drugs if applicable, will be kept constant throughout the study. All study assessments will be carried out at the time treatment is expected to cause the greatest severity of LID.
