Diagnosis of dystonic syndromes--a new eight-question approach

Dystonia is a syndrome of abnormal involuntary movements that are repetitive, twisting or patterned, and can result in abnormal postures. Dystonia may be generalized or focal, and can occur as a primary syndrome or secondary to another disease--over 50 clinical conditions are reported to cause dystonia. Classification of dystonia is based on genetic background, anatomical distribution, age at onset, and neurodegenerative processes. In many cases, manifestations of dystonia are identical regardless of the aetiology, which makes accurate diagnosis challenging, if not impossible, without additional investigations. Exhaustive lists of the causes of dystonia are not practical to aid clinicians when attempting to determine if a hyperkinetic movement can be diagnosed as dystonic. The existing diagnostic algorithms for dystonic syndromes rely on the clinician's experience, without a streamlined diagnostic pathway. Non-specialist clinicians and neurologists may, therefore, find diagnosis of dystonic syndromes difficult. In this Review, an eight-question approach is proposed, with a summary of the evidence for investigations that enable successful diagnosis of dystonic syndromes. The aim of this approach is to inform both specialists and general neurologists on the appropriate diagnostic test for each patient who presents with a possible dystonic syndrome.