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  • Updated 01.04.2021
  • Released 09.27.1993
  • Expires For CME 01.04.2024

Isolated dystonia

Introduction

Overview

Dystonia is a movement disorder characterized by patterned, twisting movements of the body that can result in abnormal postures. Isolated dystonia refers to dystonia with or without tremor but without other neurologic findings. Isolated dystonia is usually familial in children and sporadic in adults. Various forms of isolated dystonia are described in this article.

Key points

• The term “isolated dystonia” is applied when dystonia is the only movement disorder identified, with or without tremor. In contrast, the term “combined dystonia” is used when dystonia is combined with other movement disorders (such as myoclonus, parkinsonism, etc.).

• Atypical features such as cognitive impairment, seizures, pyramidal signs, and retinal findings would suggest secondary causes.

• When isolated dystonia is encountered in children and adolescents, the etiology is often genetic; whereas isolated dystonia in adults is most likely to be sporadic.

• Genetic testing should be considered in younger patients or those with a family history.

• Treatment options include oral medications, botulinum toxin injections, deep brain stimulation, and physical therapy.

Historical note and terminology

Although the term “dystonia” was first coined by Oppenheim in 1911 to describe 4 individuals who were floppy at rest but developed stiffness when they tried to move (103; 02), one of the earliest descriptions of dystonia can be found in a book of occupational diseases in 1713 by Bernardino Ramazzini, who states that “Scribes and Notaries” may develop” incessant movement of the hand, always in the same direction . . . the continuous and almost tonic strain on the muscles . . . [that] results in failure of power in the right hand” (Torres‐Russotto and Perlmutter 2008). For a large part of the 20th century, dystonia was widely considered psychogenic, until the 1970s when many characteristics of idiopathic torsion dystonia were further described (86).

There was no unified definition of dystonia until 1984, when the Dystonia Medical Research Foundation (DMRF) formulated a definition: “Dystonia is a syndrome of sustained involuntary muscle contractions, frequently causing twisting or repetitive movements, or abnormal postures” (66). This definition prevailed over the next 3 decades. However, as more was learned about dystonia, experts realized that the dystonic movements are not always sustained, slow, or twisting; rather, they can be rapid and intermittent like, for example, the blinking in blepharospasm, voice breaks in spasmodic dysphonia, dystonic tremor, and myoclonic dystonia (66). Similarly, it was realized that although dystonic movements may be tremulous or twisting, they were always “patterned.” To highlight these points, a new consensus committee supported by DMRF, Dystonia Europe, and the International Parkinson and Movement Disorder Society, revised the definition in 2013: “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” (66).

The nomenclature used to describe dystonia has evolved over time, with dystonia musculorum deformans being replaced by idiopathic torsion dystonia and then primary dystonia (18). The international panel proposed classifying dystonia along 2 axes: clinical characteristics and etiology (02). The 2013 classification has been well received in scientific literature, and more studies are adapting to its use. A review conducted in 2019 of published literature on dystonia found that of the 990 articles included in the study, 59.8% used the new classification (125).

The clinical characteristics axis includes age of onset, body distribution, temporal pattern, and associated features whereas the etiology axis comprises inherited, acquired, idiopathic causes or those due to a nervous system pathology. According to that classification, the term “primary dystonia” should not be used. It does not allow the axis classification as it has a dual meaning, referring to dystonias without other neurologic manifestations, which is a clinical characteristic, with genetic or idiopathic etiology. A preferred term is “isolated dystonia,” which encompasses dystonias without other associated movement disorders without establishing a specific etiology.

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