Clinical features, pathophysiology, treatment, and controversies of tremor in dystonia

Dystonia and tremor frequently co-occur. In some cases, they have shared biological mechanisms, while in others dystonia and tremor are two comorbid conditions. The term dystonic tremor is used to describe tremor in those who have dystonia. Two mutually exclusive definitions of dystonic tremor were proposed. According to one definition, dystonic tremor is the tremor in the dystonic body part. An alternate definition of dystonic tremor entails irregular and jerky oscillations that have saw tooth appearance with or without overt dystonia. This paper outlines the differences in two definitions of dystonic tremor and identifies their limitations. Given the diverse views defining dystonic tremor, this paper will use the term tremor in dystonia. In addition, we will outline different ways to separate the subtypes of tremor in dystonia. Then we will discuss pathophysiological mechanisms derived from the objective measures and single neuron physiology analyses of tremor in dystonia. This article is part of the Special Issue Tremor edited by Daniel D. Truong, Mark Hallett, and Aasef Shaikh.

Automated summary

Dystonia and tremor often coexist, either sharing biological mechanisms or as comorbid conditions. This paper compares and identifies the differences and limitations between two definitions of dystonic tremor, and discusses methods to separate tremor subtypes in dystonia based on objective measures and single neuron physiology analyses.