Cervical dystonia

The cervical dystonia is probably the most frequently seen type of idiopathic torsion dystonia. In the case of cervical dystonia, the abnormal involuntary contraction affects neck muscles in different distribution. It leads to the dystonic dyskinesia of the neck, which results in the dystonic posture of the head. The disorder is widely known as,spastic torticollis", and has been described under this name in the classical neurological literature. The most frequently affected muscles are sternocleidomastoid muscle, splenius capitis muscle, trapezius muscle, semispinalis capitis and cervicis muscles, levator scapule muscle and group of scalene muscles. Less frequently are affected other neck muscles, particularly muscles of the cranio-cervical area: rectus capitis maior and minor muscles, obliquus capitis maior and minor muscles, multifidi muscles and rotatores capitis muscles. There exist an indirect evidence, that deep neck muscles, as for instance longus colli muscle, can participace on the dyskinesia. However, these muscles are actually not accessible for the palpation or electromyographic (EMG) examination. Suprahyoid and infrahyoid muscles can also participate on the dystonic dyskinesia, particularly geniohyoideus muscle and mylohyoideus muscle. Muscles, which are involved in the dyskinesia, form the so-called "muscle pattern" of cervical dystonia. Cervical dystonia manifests usually in four types, which have a typical clinical pattern, and which correspond to the particular muscle pattern: torticollis, retrocollis, laterocollis and anterocollis. Nevertheless, cervical dystonia is a variable syndrome, thus the combination or overlapping of these four types might be frequent. The clinical diagnosis of fully developed syndrome is (due to its typical clinical picture) relatively easy. On the other hand, the differential diagnosis is relatively difficult. It is necessary to exclude (using all accessible paraclinical examinations) all possible causes of secondary dystonia. To further map the clinical syndrome and its characteristics, it is necessary to use EMG methods. The needle EMG, polymyography, interference pattern analysis and turns/amplitude analysis are those which are the most helpful methods to describe the detailed characteristics of cervical dystonia. Treatment of choice of cervical dystonia is botulinum toxin A (BTX). The toxin is injected into the muscles involved in the dystonic dyskinesia, either on the basis of clinical examination and palpation or with EMG guidance. The treatment effect lasts usually up to three months, then the injection must be repeated. The treatment with BTX can be complicated by the change of muscular pattern of dystonia or development of neutralising antibodies against BTX In such a case, the diagnostic process should be repeated and another serotype of BTX should be used for the further treatment.