Cervical Dystonia with Tremor: One Movement Disorder or Two?

Abstract

We thank Pandey and Jost for thoughtful comments 1 regarding our article on the diagnosis and classification of cervical dystonia (CD). 2 CD often is combined with dystonia in other body regions, and the main goal of our article was to develop empirically-derived guidelines for classification of phenomenological patterns according to body distributions affected as either focal, segmental, multifocal, or generalized.We agree tremor is common among individuals with CD 3 ; so it is important to question whether tremor should be considered when classifying body distributions affected. CD plus tremor of the head/neck would be considered a focal dystonia, because only one body region is affected. However, the combination of CD plus hand tremors would be considered a focal dystonia if only the dystonia is considered, but a multifocal dystonia if the hand tremors are also considered. An important point to consider is that consensus statements for dystonia 4 and tremor 5 have encouraged separation of phenomenology (Axis I) from etiology (Axis II). In keeping with these recommendations, results from our study 2 indicate that most movement disorder specialists do not consider tremor when classifying dystonia according to body distribution, at least at the phenomenological level. In other words, they view dystonia and tremor as two independently ascertainable motor phenomena. The separation of these two motor phenomenologies (Axis I) does not mean that there may be certain etiologies (Axis II) where tremor and dystonia are combined. However, our prior study did not address etiology.We also agree that clinical rating scales for dystonia have limitations, particularly when it comes to tremor. Despite the high co-prevalence of tremor and dystonia, the most popular dystonia scales do not assess tremor. Dystonia Coalition investigators recently revised and re-tested the most popular CD scale (TWSTRS), adding an item for head tremor to address this important shortcoming. 6 The tremor item did not fare well on a standard clinimetric property that assesses the item-to-total correlation. This property tests how one item relates to all of the rest of the items combined. The poor item-to-total correlation for the tremor item means that tremor severity did not correlate