Objective: To develop a chronic pain (CP) classification and scoring system for dystonia.

Background: CP is prevalent in dystonia and significantly impacts patient’s quality of life (QoL). CP’s treatment and management is hampered by the lack of validated CP in dystonia.

Method: Movement disorders and pain specialists along with dystonic patients developed the Dystonia-Pain Classification System (Dystonia-PCS) to provide a pain severity score encompassing pain intensity, frequency, and impact on daily living and, also, to classify CP as related or unrelated to dystonia. Afterwards, a cross-sectional multicenter validation study recruited consecutive patients with inherited/idiopathic dystonia of any distribution, with or without CP. The Dystonia-PCS was compared to pain, mood, Qol, and dystonia scales (Brief Pain Inventory-BPI, Douleur Neuropathique-4 questionnaire-DN4, Hospital Anxiety and Depression Scale, EuroQol-5D-3L and Burke–Fahn–Marsden Dystonia Rating Scale).

Results: 65,85% of patients had CP (n=81 of 123 recruited patients). Most patients had CP directly related to dystonia (82.7%), followed by aggravated by dystonia (8.8%), and non-related to dystonia (7.5%). Dystonia-PCS had excellent internal consistency (ICC=0.925, p<0.0001) and intra-rater (ICC 0.941) and inter-rater (ICC 0.867) reliability. Most patients had cervical pain, followed by cephalalgia and low back pain. Dystonia-PCS score correlated with EuroQol-5D-3L’s pain subscore (r=0.635, p<0.001), BPI severity and interference subscores (r=0.553, p<0.001 and r=0.609, p<0.001, respectively).

Conclusion: Dystonia-PCS is a reliable tool to quantify CP impact in dystonia and may be used in future studies to understand CP and its treatment, as well as, to quantify CP improvement after dystonia’s treatment.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/presenting-the-dystonia-pain-classification-system-dystonia-pcs/