Effect of Vibro-tactile Stimulation Intensity on Head Posture in Cervical Dystonia

The primary goal of this clinical trial is to examine the effects of cervical vibrotactile stimulation intensity on abnormal head posture in people with cervical dystonia. The main question is: Does higher vibration intensity correct head posture to a greater extent than lower vibration intensity? Researchers will compare the head posture of participants with cervical dystonia who receive different intensities of vibration to cervical muscles. The secondary goal of this clinical trial is to examine the degree of proprioceptive impairment in cervical dystonia. Specifically, the study will assess proprioceptive impairment at the neck, wrist, and ankle joints, and seeks to determine whether the impairment improves with cervical vibrotactile stimulation. Researchers will compare the proprioception testing results of these joints between cervical dystonia patients and age- and sex- matched healthy controls. Researchers will also compare the neck proprioception testing results of cervical dystonia patients before and after stimulation. Participants will visit the lab once for three hours, where they will go through: 1. clinical questionnaires; 2. neck, wrist, and ankle proprioception testing, 3. vibrotactile stimulation where they sit and relax 4. neck proprioception testing

Inclusion Criteria: Confirmed diagnosis of adult-onset, isolated idiopathic cervical dystonia. Exclusion Criteria: History of other neurological diseases, including Parkinson's disease, essential tremor, dementia, etc. History of peripheral nervous system disease that can impair proprioception. Deep brain stimulation implanted or denervation surgery. UBACC score lower than 15. Severe head tremors or facial muscle contractions. Regular intake of benzodiazepines or antidepressant medication.