This study addresses postures and range of motion in cervical dystonia (Spasmodic Torticollis). It uses 3D miniature and wireless motion captures sensors, and aims to increase the understanding of the biomechanics of the movement disorders of the cervical column in this pathology. In addition, the clinical state of cervical dystonia of the patients will be assessed, using the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS). The investigators will compare the results between control and study groups.

Inclusion Criteria:

• Segmental cervical dystonia diagnosed by a neurological specialist in movement disorders

Exclusion Criteria:

• Neurological pathology other than cervical dystonia such as Parkinson's disease, head tremor, severe pain or cervical ailment, which would have required a treatment within the last six months
• Neuroleptic treatment in course
• Pregnancy
• breast feeding

Study-group: 30 patients meeting the criteria for cervical dystonia (Spasmodic Torticollis) and without botulinum toxin injections during the last 6 previous months before baseline. Patients will be selected consecutively among the outpatients with movement disorder of 3 study sites: Fondation OPH Rothschild, Salpetriere Hospital and Sainte-Anne Hospital (Paris)

Control-group: 30 healthy volunteers matched in age (+/- 5 years) and gender with the 30 CD subjects. They will be selected in Sainte-Anne Hospital (Paris)