Botulinum toxin treatment for spasmodic torticollis

Abstract

Spasmodic torticollis is the most common focal dystonia which has an estimated prevalence of 300 persons per million. It is characterized by sustained neck contractions that force the head to deviate from its normal position. Patients are distressed by neck pain, functional disability and social embarassment. Abnormal postures of the head result from twisting the head towards the shoulder (torticollis), tilting the head towards the shoulder (laterocollis), extending the head (retrocollis) or flexing the head (anterocollis). The efficacy and safety of botulinum toxin in the treatment of cervical dystonia have been demonstrated in several controlled studies. Botulinum toxin is a neurotoxin which produces a chemical denervation of the motor endplate. It inhibits the exocytosis of acetylcholine by decreasing the frequency of acetylcholine release. Since its introduction in the early 1980s, the use of botulinum toxin has improved the quality of life of patients affected by focal dystonia. As many as 50%-90% of patients have marked relief of their neck pain and obtain a substantial improvement in both function and control of head and neck movement. The most important determinants of a favorable response to treatment with botulinum toxin are the dose, the proper selection of the involved muscles and the times of injection. Electromyographic guidance to identify the most active muscles is requested. Three to four injection sites per muscle may be more effective than a single injection. The treatment can induce reversible side effects including dysphagia (after injection in sternocleiomastoid muscles), weakness of the neck muscles, malaise, pain at the injection site. Systemic effects are of scarse clinical importance. A minority of patients produces antitoxin antibodies.