Dancing Dorsal Quadrilaterals: A Novel Peripherally Induced Movement Disorder.

Importance: Recognized peripherally induced movement disorders include the painful legs moving toes syndrome, postamputation dyskinesias, and belly dancer dyskinesias. Objective: To introduce and characterize the dancing dorsal quadrilaterals, a novel peripherally induced movement disorder that predominantly affects dorsal quadrilateral muscles (trapezius and rhomboids) after upper spine instrumentation. Design, Setting, and Participants: Between 1990 and 2015, a total of 4 patients who developed abnormal movements of the dorsal quadrilateral muscles after upper spine instrumentation were referred to movement disorders clinics at 3 academic medical centers in the United States, Canada, and Argentina. A prospective and retrospective analysis of the clinical and electrophysiologic characteristics of their abnormal movements is presented in this brief report. Data were analyzed between July 2015 and January 2018. Exposures: Extensive upper spine instrumentation complicated with misalignment and prolonged postsurgical neuropathic pain. Main Outcomes and Measures: Video documentation of clinical and electrophysiologic characteristics of dancing dorsal quadrilaterals. Results: Four patients with upper spine disease (2 women and 2 men, ranging in age from early 30s to early 70s) required extensive surgical manipulation and instrumentation that was complicated by misalignment, prolonged dorsal neuropathic pain, and unusual abnormal movements. These movements consisted of semirhythmic, repetitive writhing, and jerky movements of the scapular region with distinctive rotatory motions. They are referred to as the dancing dorsal quadrilaterals because they predominantly affected the bilateral trapezius and rhomboids (dorsal quadrilateral muscles) but could spread to adjacent muscles, and they are similar in appearance and possibly pathogenesis to "belly dancer" dyskinetic movements. The movements of the dancing dorsal quadrilaterals occur when upright but not when lying down or during voluntary muscle activation. Sensory stimulation also diminishes the movements. Long-duration bursts of normal motor unit potentials with normal recruitment pattern were evidenced. Conclusions and Relevance: The dancing dorsal quadrilaterals syndrome represents a further example of a peripherally induced movement disorder characterized by neuropathic pain preceding a regional movement disorder following soft-tissue or nerve injury.