Role of the vestibular system in the pathophysiology of spasmodic torticollis

Idiopathic spasmodic torticollis is a form of focal dystonia affecting the neck. It is characterised by involuntary repetitive or sustained neck muscle contractions leading to abnormal head postures and impaired control of head movement.1-3 With an estimated prevalence of 9/100 0004 spasmodic torticollis is the most common focal dystonia. Onset peaks around the age of 40 and there is a female preponderance with a sex ratio of about 1.5:1.5 Symptoms typically start gradually over a period of days or weeks and remain largely confined to the neck although spread of dystonia to the face (blepharospasm, oromandibular dystonia), larynx (laryngeal dystonia), and arms (dystonic arm postures and writer's cramp), but not the legs, can occur.1 Abnormal head and neck postures in spasmodic torticollis cause considerable disability, often interfering with the patient's ability to work, and cause pain, social stigmatisation, and depression.6 Most cases are sporadic. However, a family history is reported in about 15% of patients1 and several families with more than four affected members have been described,7-12 all of whom showed autosomal dominant inheritance. Thus genetic factors seem to have some aetiological importance.