It has previously been pointed out that the diagnosis of "dystonia" has been indiscriminately applied to all cases in which dystonic symptoms appear. Dystonia defined in this way was, therefore, to be regarded "merely as a variety of extrapyramidal disease whose motor disorder is predominantly dystonic in order, rather than a distinct clinical entity" (Keschner). In principle, the indiscriminate grouping together of conditions with different causes hampers further investigation. The concept of a cerebral disease entity should always be based on the occurrence of a well outlined constellation of clinical symptoms produced by a distinct pathologic process affecting certain structures of the brain. As long as the clinical picture of dystonia cannot be correlated with a definite pathologic lesion, the function of a preliminary clinical investigation is to establish clinical groups which are as homogeneous as possible; later one may try to correlate this preliminary clinical grouping with the pathologic