Objective: To evaluate domain coverage of rating scales used to quantify motor severity of blepharospasm (BSP).

Background: BSP rating scales have been evaluated for their clinimetric properties [1], and the Jankovic Rating Scale (JRS) in particular evaluated for its relationship to patient self-assessments and sensitivity to clinically meaningful change [2].  However, the scales have not been assessed for their domain coverage.

Method: We evaluated domain coverage (aka “content representation” in psychometrics) for five rating scales used for measuring BSP motor severity:  Global Dystonia Rating Scale (GDRS), Burke-Fahn Marsden Scale (BFM), Jankovic Rating scale (JRS), Blepharospasm Severity Rating Scale (BSRS), and the Blepharospasm Phenotyping Tool (aka “Blepharospasm Mini”, under development). In each case, based on the observable phenomenological elements of each scale, we identified “gaps”:  phenomenon combinations for which there is no score.

Results: The GDRS has no gaps because scores are textually anchored by only gross severity level.   However, all of the other BSP rating scales have gaps.  Specifically, the wording of the textual anchors creates many more possible phenomenological combinations than are available from the available scores. For example, the JRS has two options for “blinking” (normal, increased), three options for “fluttering” (none, mild, severe), and three options for spasms (none, moderate, severe), producing 2 x 3 x 3 = 18 possible combinations.  For 13 of the possible combinations, it is unclear how they map to one of the five possible scores.

Conclusion: Most rating scales used to quantify BSP motor severity suffer from incomplete domain coverage.  This can introduce systematic measurement bias, decrease construct validity, and decrease sensitivity. The “eyes and upper face” item in the GDRS is the simplest scale and does not exhibit incomplete domain coverage.  However, it lacks the phenomenological detail which should be relevant for the rich heterogeneity in the presentation of BSP.  Ongoing developments in objective measures for BSP motor severity should facilitate both goals:  more complete domain coverage and the ability to capture relevant overt phenotypical features of BSP.

References: [1] Defazio, G., Hallett, M., Berardelli, A., Perlmutter, J. S., Berman, B. D., Jankovic, J., Bäumer, T., Comella, C., Ercoli, T., Ferrazzano, G., Fox, S. H., Kim, H., Moukheiber, E. S., Pirio Richardson, S., Weissbach, A., Gigante, A. F., & Jinnah, H. A. (2022). Measurement Properties of Clinical Scales Rating the Severity of Blepharospasm: A Multicenter Observational Study. Movement Disorders Clinical Practice, 9(7), 949–955. https://doi.org/10.1002/mdc3.13530

[2] Jankovic, J., Kenney, C., Grafe, S., Goertelmeyer, R., & Comes, G. (2009). Relationship between various clinical outcome assessments in patients with blepharospasm. Movement Disorders, 24(3), 407–413. https://doi.org/10.1002/mds.22368

« Back to 2026 International Congress

MDS Abstracts - https://www.mdsabstracts.org/abstract/phenomenological-gaps-in-rating-scales-for-blepharospasm-motor-severity/