• Change in the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS)with 3 weeks of active treatment compared to placebo [ Time Frame: beginning and end of each treatment ] [ Designated as safety issue: No ]
  

• To determine the rate and severity of adverse events within and between participants [ Time Frame: Beginning and end of each treatment ] [ Designated as safety issue: Yes ]
  
• To observe changes within and between participants in the Global Impression Scale (GIS) [ Time Frame: End of each treatment ] [ Designated as safety issue: No ]
  
• To observe changes within and between participants in the Visual Analog Pain Scale [ Time Frame: beginning and end of each treatment ] [ Designated as safety issue: No ]
  

Drug: Dronabinol
2.5 mg tablets; titrated over 14 days and 7 days steady dose

The study is a double-blind, randomized, placebo-controlled, crossover, phase II study of dronabinol versus placebo. Thirty patients with idiopathic cervical dystonia will be enrolled in the study. Patients will be randomized to either dronabinol or placebo by a computer-generated random numbers table that will be kept in the central pharmacy until the end of the trial. Only the central pharmacy will be aware of treatment allocation; all others will be blinded for the duration of the trial.

Regardless of treatment allocation, study participants will begin taking their assigned study medications on Day 1, increasing the "dose" (actual increase in dose for dronabinol-assigned arm, fictional increase in dose for placebo-assigned arm) every 3 days. At the end of the third week, on Day 21, the study participant will complete the first phase of study medication and remain off study medication for a period of two weeks, and will have a planned study visit. On Day 36, the study participant will have a planned study visit, the new medication will be dispensed, and the participant will begin taking the other arm of the study medication for a period of 3 weeks, in the same manner as the first arm. At the end of the 3 weeks (8 weeks in total), the study participant will discontinue the assigned study medication and will attend a planned study visit for study termination. At each visit, patients will be assessed with a medical and neurological history and examination and a video recording made for post hoc analysis of TWSTRS by a rater blinded to the treatment arm.

The main issue with compliance to study medication will relate to side-effects. Side-effects are mainly dose related and can be minimized with a dose escalation protocol, which is planned in this study. Compliance and adverse effects will be monitored by weekly phone calls for side effects and pill counts at the end of each treatment arm.