The Use of Botox in Advanced Parkinson's Patients Experiencing Pain

The investigators will perform a double-blind, randomized cross-over study evaluating the efficacy and safety of an individual pattern of BTXA injections targeted at painful muscles vs. placebo injection. Primary outcome will be a measure of global pain as perceived by the participants. To assess this endpoint the investigators will use:1. change in pain on a Numeric Rating Scale (NRS) by telephone between BTXA and placebo injections at 4 week post injection and 2.change in Visual Analogue Scale (Edmonton Symptom Assessment System: Numerical Scale) at study visits. Secondary outcomes will be the percentage of responders, Physician rated Clinical Global Impression (CGI), Unified Parkinson Disease Rating Scale (MDS-UPDRS) on medication, quality of life by Parkinson Disease Questionnaire (PDQ-39) and adverse events as assessed at each study visit.