Safety and Effectiveness of Valbenazine as Adjunct Therapy to Botulinum Toxin Injections in Cervical Dystonia

Eligibility Criteria

• * Idiopathic CD (neck musculature first and most prominently affected)
• * 18-75 years old (participants excluded if their dystonia symptoms began before age 18 as childhood-onset dystonia typically represents a genetic and/or primary generalized form of dystonia)
• * Onset of dystonia ≥18 years old, no known hyperkinetic movement disorder-related genetic mutation
• * Dystonia severity more than minimal and not very severe as defined by Toronto Western Spasmodic Torticollis Rating Scale-2 Motor Severity (TWSTRS-2-Severity) score ≥ 5 and ≤ 20.
• * Stable on botulinum toxin injections last 90 days (BoNT dose change \<10% and patient reported stability of response over last two injection cycles)
• * Stable on other neuroactive medications.
• * History of deep brain stimulation
• * History of uncontrolled or untreated depression in the prior 3 months, suicidality, or history of suicide attempts
• * History of uncontrolled liver disease or failure
• * History of tardive dyskinesia or tardive dystonia
• * Currently taking dopaminergic and/or anti-dopaminergic medications including VMAT2 inhibitors or other antipsychotic medications
• * Exposure to dopaminergic and/or anti-dopaminergic medications including VMAT2 inhibitors or other antipsychotic medications in the last 30 days -Presence of parkinsonism or other movement disorder other than dystonia on exam -Receiving botulinum toxin injections at a planned frequency other than every 3 months or typically receive injections at intervals \<11 weeks or \>13 weeks -Known history of long QT syndrome or cardiac tachyarrhythmia or any clinically significant cardiac abnormality.
• * Prolonged QTc as defined by \> 450 msec for men and \> 470 msec for women