Tasks for assessing dystonia in young people with cerebral palsy

Abstract

Background: Dystonia in childhood is typically associated with cerebral palsy (CP). Dystonia severity scales for CP require prolonged exam protocols with numerous tasks, often making them onerous for routine clinical use.

Objective: To identify which individual tasks best approximate dystonia severity compared to the gold standard full protocol.

Methods: In this cross-sectional study, comprehensive exam protocol videos were taken during routine care of ambulatory people with CP age 5 and up. Five pediatric dystonia experts reviewed individual tasks and the full protocol for dystonia using the Global Dystonia Severity Rating Scale. Experts' written scoring justifications were qualitatively analyzed to determine commonly cited features of dystonia.

Results: When examining the difference in dystonia severity ratings between each task and the full protocol, seated upper extremity tasks had the lowest variance (p<0.05, F-test) and had lower score differences than the stand/walk/run and seated lower extremity tasks (p<0.05, repeated measures Friedman test). Experts most commonly identified the following movements as dystonic: wrist flexion (8.4% of all movement statements), finger flexion (7.3%), wrist ulnar deviation (6.8%), toe dorsiflexion (8.4%), ankle inversion (7.9%), and ankle plantarflexion (6.4%). Experts rated dystonic movements as more severe if they were consistently triggered by multiple stimuli (26.8% of all severity statements) or functionally impactful (20.7%).

Conclusions: Seated upper extremity tasks may be valuable for identifying dystonia and estimating its severity during routine clinical care. Clinical dystonia severity assessment could be guided by assessing specific dystonic movements, the consistency with which they are triggered, and their functional impact. Cerebral palsy is the most common motor disability across the lifespan and is commonly associated with dystonia, a debilitating, frequently painful, and often treatment refractory movement disorder.^1-3 Dystonia in CP affects up to 2 of every 1000 people in the US, comparable to the prevalence of Parkinson's disease.^3-5 However, despite its high prevalence and high impact, there are no data-driven treatment paradigms for dystonia in CP.^6,7 Developing data-driven treatments requires the ability to assess dystonia severity in a standardized way across centers to facilitate large scale clinical trials. However, current dystonia severity assessments have been criticized for requiring prolonged video recordings or in person assessments (often lasting more than 30 minutes).^8,9 This can be both expensive (requiring many personnel hours) and exhausting for people with CP to execute. Furthermore, the longer these severity assessments take, the less feasible they are to execute during routine clinical care, making it difficult to clinically assess the impact of dystonia treatments. Therefore, of the many tasks currently used across dystonia severity assessments, it would be valuable to determine the subset of tasks most useful for assessing dystonia in young people with CP.

Keywords: cerebral palsy; dystonia; pediatric movement disorders.

Figure 1.

Comparison of Global Dystonia Severity Rating Scale (GDRS) scores across tasks. Data points are GDRS scores or score differences per expert rater per subject. *p<0.05 for repeated measures Friedman test and post-hoc Dunn’s test comparing each task grouping and the full protocol (left) or comparing task groupings (right). U/LE – upper/lower extremity.

Figure 2.

Comparison of movement and severity features cited by experts while assessing dystonia across tasks. *p<0.05 for Chi-square test with Yates correction followed by post-hoc Chi-square tests with Bonferroni correction for multiple comparisons of code frequencies between tasks. UE – upper extremity. LE – lower extremity