[New approaches in dystonia (clinical features, genetic issues and pathophysiology]

Dystonia is defined by the occurrence of abnormal twisting movements and posture, and may be generalized or focal. Many subtypes of dystonias have been described, including monogenic forms (eg. DYT1 and DYT6), secondary dystonias related to metabolic disorders, forms due to brain lesions (including post-anoxic brain injury), and tardive dystonia. Dystonia may also be associated with myoclonus (myoclonus-dystonia, DYT11) or parkinsonism (rapid-onset dystonia parkinsonism DYT1). Paroxystic dystonias are a subgroup of paroxysmal dyskinesias. Diagnosis is based mainly on clinical features, age at onset, outcome, associated neurological signs, and brain MRI. Until recently, basal ganglia dysfunction and alterations of the sensory-motor network with maladaptive cortical plasticity were the core pathophysiological features of dystonia. Cerebellar and cerebello-thalamic anatomic-functional abnormalities may also play a role. The main objectives of this review are to highlight the principal characteristics of dystonias and to provide an overview of known culprit genes and environmental factors. Current pathophysiological knowledge, including anatomic-functional abnormalities, is summarized.