Cervical dystonia severity scale reliability study

Abstract

Cervical dystonia (CD) is characterized by sustained contractions of the neck musculature, resulting in abnormal head postures. The Cervical Dystonia Severity Scale (CDSS) was developed to provide a reliable measure of treatment response in patients with CD. The CDSS uses a protractor and wall chart to rate the severity of the head's deviation from neutral in each of three planes of motion (rotation, laterocollis, anterocollis/retrocollis), which is then scored in 5 degree intervals (1 degree to 5 degrees deviation = 1; 86 degree to 90 degrees deviation = 18). To test the reliability of the CDSS, four centers, each with two independent examiners, evaluated 42 patients with CD. At each site, each of the two examiners used the CDSS to evaluate the head position of each patient twice, on the same day, for a total of four evaluations. The kappa value for intra-examiner agreement was 0.94 (95% confidence limit of 0.900-0.972), indicating excellent intra-examiner reliability. The kappa value for interexaminer reliability was 0.79 for the first evaluation and 0.86 for the second evaluation (95% confidence limits of 0.668-0.920 and 0.790-0.920) indicating excellent interexaminer reliability. Thus, the CDSS was highly reliable in both intra-examiner and interexaminer scoring comparisons.