Effectiveness of Botox on Reducing Rest Tremor in Parkinson's Disease

Purpose: Rest tremor in Parkinson's disease is notoriously difficult to treat through pharmacological measures, currently only predictably attenuated by the invasive deep brain stimulation surgery. The investigators hope to find some predictable and clinically meaningful attenuation of tremor with targeted use of onabotulinum toxin on muscles involved in creating the tremor. Participants: 16 subjects who meet United Kingdom (UK) brain bank criteria for Parkinson's disease with medically refractory rest tremor of at least 3 cm amplitude. Procedures (methods): Subjects will be blinded to receive either sham saline injection versus onabotulinum toxin injections directed to muscle groups felt to be clinically involved in causing the oscillatory movement of the tremor. Assessment of tremor severity and functional improvement from baseline after injection will occur within group (i.e. each subject will serve as their own control). Hypotheses: 1\. (A) Onabotulinumtoxin A significantly attenuates the amplitude of medically-refractory rest tremor of the upper limb in Parkinson's patients as compared to sham injections; as measured by reduction in the Movement Disorders Society Unified Parkinson's Disease Rating Scale (MDS-UPDRS) tremor subscore. 1\. (B) Onabotulinumtoxin A significantly improves the limb function of Parkinson's patients with medically-refractory rest tremor of the upper limb as compared to sham injections; as measured by an increase in Action Research Arm Test (ARAT) scores.