The New Classification System for the Dystonias: Why Was it Needed and How was it Developed?

Abstract

The term dystonia originated in 1911 with Oppenheim’s description of 4 individuals who were floppy at rest, yet developed stiffness when they tried to move. He believed the core problem was a defect in muscle tone, so he coined the term dys-tonia, which literally means abnormal muscle tone. Over the next decades, additional clinical manifestations of dystonia were recognized, and various authorities began to alter Oppenheim’s definition according to their own views. It was not until 1984 that the Dystonia Medical Research Foundation (DMRF) created a committee to develop a more unified definition: “Dystonia is a syndrome of sustained involuntary muscle contractions, frequently causing twisting or repetitive movements, or abnormal postures.” In the decades that followed this definition, more was learned about the manifestations of dystonia, and expert opinions again led to varying adjustments to the definition. As a result, a new consensus committee revised the definition. This committee was again supported by the DMRF, but also by Dystonia Europe, the International Parkinson and Movement Disorder Society (formerly the Movement Disorders Society), and an international panel with broad expertise in the clinical and biological basis of the dystonias: “Dystonia is a movement disorder characterized by sustained or intermittent muscle contractions causing abnormal, often repetitive movements, postures, or both. Dystonic movements are typically patterned, twisting, and may be tremulous. Dystonia is often initiated or worsened by voluntary action and associated with overflow muscle activation.” The essential change was the addition of the word intermittent and two other sentences. The word intermittent was added to address the frequent misconception that dystonic movements are always sustained, slow, or twisting. Examples of rapid, intermittent dystonic movements include blinking in blepharospasm, voice breaks in spasmodic dysphonia, tremor-dominant dystonias, and myoclonic dystonia. One sentence was added to emphasize that the varied clinical manifestations may be tremulous or twisting, but they tend to be patterned. The second sentence was added to emphasize characteristic worsening with voluntary action, a feature noted in Oppenheim’s original concept.