Objective: A new writer’s cramp impairment scale (WCIS) was created and is compared with the existing writer’s cramp rating scale (WCRS).

Background: Writer’s cramp (WC) is characterized by cramping and abnormal posturing of the hand while writing leading to significant disability.  Studies on WC have been hampered by the lack of reliable objective scales.  The WCRS, a validated quantifiable scale, has been helpful, but its utility is limited because it does not capture many aspects of dystonic motor impairment and has low inter-rater reliability.  We developed the WCIS by expanding the WCRS to incorporate additional elements.  Here we compare the WCRS with the new WCIS.

Method: Eight patients with WC and eight age- and handedness-matched healthy volunteers (HV) were compared using the WCRS and WCIS.  Participants performed standardized writing tasks while being videotaped according to a standardized video procedure.  WC patients receiving botulinum toxin (BoNT) treatment were required to wait a minimum of 3 months for the effects of the last BoNT procedure to have worn off before participating in this study.  Each subject’s videotape was scored twice using the WCRS and WCIS by 4 blinded raters, with each rating separated by at least a one-week interval.  Both inter-rater and intra-rater reliabilities were measured.

Results: Inter-rater and intra-rater reliabilities for the WCIS and WCRS are shown in the table.  Inter and intra-rater reliabilities for WCIS were more robust than that for the WRCS in this analysis.

Table

Footote to the table:  kappa values 0.0 to 0.2 = slight agreement; 0.21 to 0.40 = fair agreement; 0.41 to 0.60 = moderate agreement; 0.61 to 0.80 = substantial agreement; 0.81 to 1.0 = almost perfect or perfect agreement.  ICC values less than .40 = poor agreement; .40 and .59= fair agreement; .60 and .74 = good agreement; .75 and 1.0 = excellent agreement. PGR=Physician Global Rating.

Conclusion: These results suggest higher reliability for WCIS than for WCRS based on both intra- and inter-rater reliability measures. The WCIS will require validation with larger sample sizes. The WCIS is a lengthy scale so a principal components analysis may help identify score-driving components to make it more efficient.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/validating-a-new-writers-cramp-impairment-scale/