Primary Dystonia

Abstract

Abstract Dystonia syndromes are defined by the occurrence of sustained muscle contractions, which frequently cause twisting and repetitive movements or abnormal postures. Classification of dystonia syndromes is based on three axes describing, for each patient, age at disease onset (early vs adult), distribution of involved body sites (from focal to generalized), and aetiology (primary, heredodegenerative, or symptomatic forms). Primary dystonias are further subdivided into primary pure (with dystonia only), primary-plus (with other associated movement disorders) and primary paroxysmal (characterized by intermittent symptoms). The phenomenology of dystonia encompasses a combination of movements and postures to generate sustained muscle contractions, repetitive twisting movements, and postural (torsion) abnormalities. Dystonic postures can precede the occurrence of movements, and in rare cases can persist without the appearance of movements (so-called fixed dystonia). In dystonic movements speed of contractions may be slow or rapid, but is commonly sustained at the peak, making movements acquire a consistent directional or posture-assuming character. Dystonia has some unique activation/deactivation features: geste antagoniste (or sensory tricks), mirroring, and overflow. It has been shown that both genetic predisposition and environmental factors play a significant role in the aetiology of primary dystonia syndromes. Genetic defects are known for two primary pure dystonias (namely, DYT1 and DYT6) and for several primary-plus, paroxysmal, and heredodegenerative dystonia syndromes. There is no aetiological or neuroprotective treatment for primary pure dystonias. Symptomatic treatments aim to relieve involuntary movements, correct abnormal postures, prevent contractures, reduce pain and embarrassment, and improve function. Botulinum toxin is the first choice treatment for most types of focal dystonia. Neurosurgical treatments have a growing role in the symptomatic management plan since long-term electrical stimulation of the globus pallidus internus has been established to be effective for primary generalized or segmental dystonias.