 Primary Cervical Dystonia PCD is the most common type of focal dystonia. In addition to pain, PCD is associated with disability in many activities of daily living; social stigma and embarrassment; and decreased quality of life. Botulinum toxin BoNT therapy is the gold standard for treatment of PCD. Although effective in improving dystonia symptoms, BoNT injections have been associated with suboptimal improvements and the benefits of BoNT may last shorter than the expected time frame of 12 weeks. PCD subjects are referred for deep brain stimulation surgery if there is poor or inconsistent response to medical treatment. In addition to the need for repetitive injections, subjects may suffer from side effects such as neck pain, muscle weakness, head drop, breathing difficulty, and swallowing issues. BoNT therapy outcomes are not likely to improve until and unless the investigators understand the underlying mechanisms of action. 