Cervical dystonia Muscle selection for botulinum toxin treatment

Cervical dystonia (CD) is a movement disorder characterized by sustained involuntary muscle contractions leading to abnormal postures, pain and twisting movements of the neck. The primary treatment of CD are injections with botulinum toxin (BoNT) in the dystonic muscles. One of the most important determinants of a good treatment response is adequate selection of the dystonic muscles. However, there is still much debate about the best approach to select dystonic muscles for BoNT treatment. In this thesis, we performed a systematic review of the literature to determine what the best currently existing method is for muscle selection. In addition, we performed a retrospective analysis of BoNT treatment outcome in our tertiary referral centre. We concluded that clinical evaluation combined with polymyographic EMG recordings (polymyography) is the best approach to identify dystonic muscles for BoNT treatment. Polymyography should at least be considered in patients with an unsatisfactory response to BoNT treatment with clinical evaluation alone. Another goal of this thesis was to develop and evaluate several new methods to improve the identification of dystonic muscles. EMG coherence analysis and EMG autospectra analysis revealed differences between dystonic and non-dystonic muscles, but their ability to improve BoNT treatment outcome still needs to be determined. These findings might lead to new pathophysiological research as these autospectral changes might provide more insight in the pathophysiology of CD.