BACKGROUND: The Dyskinesia Impairment Scale (DIS) is a new assessment scale for 
dystonia and choreoathetosis in children and youth with dyskinetic cerebral 
palsy. Today, the Burke-Fahn-Marsden Dystonia Rating Scale (BFM) is mostly used 
to assess dystonia in children with inherited dystonia. The aim of this study 
was to assess reliability and validity of the DIS in children and youth with 
inherited or idiopathic dystonia.
METHODS: Reliability was measured by (1) the intraclass correlation coefficients 
(ICCs) for inter-rater and test-retest reliability, as well as (2) standard 
error of measurement (SEM) and minimal detectable difference (MDD). For 
concurrent validity of the DIS-dystonia subscale, the BFM was administered.
RESULTS: In total, 11 males and 9 females (median age 16 years and 7 months, 
range 6 to 24 years) were included. For inter-rater reliability, the ICCs for 
the DIS total score and the dystonia and choreoathetosis subscale scores were 
0.83, 0.87, and 0.71, respectively. For test-retest reliability, the ICCs for 
the DIS total score and the dystonia and choreoathetosis subscale scores were 
0.95, 0.88, and 0.93, respectively. The SEM and MDD for the total DIS were 3.98% 
and 11.04%, respectively. The Spearman correlation coefficient between the 
dystonia subscale and the BFM was 0.88 (p < 0.01).
CONCLUSIONS: Good to excellent inter-rater, test-retest reliability, and 
validity were found for the total DIS and the dystonia subscale. The 
choreoathetosis subscale showed moderate inter-rater reliability and excellent 
test-retest reliability. The DIS may be a promising tool to assess dystonia and 
choreoathetosis in children and young adults with inherited or idiopathic 
dystonia.