To the Editor We read with interest the article by Lizarraga et al1 describing 4 patients with a novel peripherally induced movement disorder (PIMD) labeled as “dancing dorsal quadrilaterals (DDQ).”1 However, there are several concerns regarding the pathogenesis of these movements. First, in 2 of 4 cases (50%) presented by the authors, abnormal movements appeared over a period of 2 years after spine instrumentation. The diagnostic criteria for PIMD, while never validated, typically suggest 1 year as a maximum time delay between the injury and the onset of the movement.2 This is important in establishing an association, particularly if pending litigation and secondary gain are involved. In such cases, the distinction between PIMD and functional movement disorder (FMD) is complicated, as FMD may also be preceded by a physical injury. Second, the authors note that the DDQ and other PIMD are abolished or suppressed with sensory stimuli or during voluntary movement, but it is also true that FMD may disappear during these maneuvers.
Chouksey A, Pandey S, Hallett M. Dancing Dorsal Quadrilaterals—Organic or Functional? JAMA Neurol. Published online July 01, 201976(8):985. doi:10.1001/jamaneurol.2019.1717
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