Dystonias: Secondary dystonias: clinical analysis and diagnostic approach

Definitions: Dystonia is a muscle contraction disorder marked by sustained involuntary clonic contortions or abnormal posture. Primary dystonias can b e divided into familial forms related to genetic anomalies and idiopathic f orms. Secondary dystonias are related to an underlying neurological disease . Metabolic diseases: Secondary dystonias related to metabolic diseases gener ally occur early before puberty although late onset forms have been describ ed. Other signs, in association with the dystonia, include mental retardati on, epilepsy, cerebellous or pyramidal signs, oculomotor disorders or a neu ropathy. Occasionally, extraneurological signs suggest the diagnosis. Biolo gical markers are known for most of these dystonias. Event-related diseases: In some cases, the dystonia is the only sign and de velops as a sequela to an earlier neurological event such as neonatal anoxi a, trauma, vascular event or adverse effect of neuroleptics. Hemi-dystonias: Dystonias limited to one side are generally secondary.