Objective: To determine the usefulness of posturography as an objective measure of disease progression and prognostication on Progressive Supranuclear Palsy (PSP).

Background: To date, interventional trials in PSP mostly rely on the PSP rating scale (PSP-RS) as a primary outcome measure to evaluate disease modification. Objective parameters such as MRI volumetry or PET data often serve as secondary outcome parameters. However, objective measures of postural stability are usually not included.

Method: Participants in the PROSPERA trial to evaluate rasagiline versus placebo in PSP Richardson’s Syndrome (NCT01187888) underwent posturographic measurements at up to five time points over one year using an inert recording platform with piezoelectric elements (9281A, Kistler Instrumente AG, Winterthur, Switzerland). Patients were positioned upright without support, and recordings were conducted for 30 seconds in two conditions, eyes open (EO) and eyes closed (EC). Total sway and root mean square (RMS) were analyzed. Clinical parameters included PSP-RS, UPDRS part III and overall survival if available from clinical records. Survival analyses were conducted using Kaplan-Meier curves as well as Cox proportional hazard ratios.

Results: A total of 156 posturographic measurements were obtained in 44 participants, with 6 and 12 month follow-up data available from n = 34/22 patients. Survival data were available for 38 patients. Total sway, but not RMS markedly increased at 6 (EO p=0.0014, EC p=0.06) and 12 months (EO p=0.0004, EC p=0.023). Sample size calculations yielded a required size of n=146 per treatment group to detect a 50% treatment effect at a power of 0.8. At baseline, total sway correlated with total UPDRS part III scores, but not PSP-RS total scores. In addition, RMS scores predicted overall survival (EO: hazard ratio 1.098 (1.030-1.162) EC: hazard ratio 1.001 (1.000-1.001)).

Conclusion: In summary, posturography appears to be suitable as a measure of disease progression, although our data indicate that rather large sample sizes would be required to detect therapeutic effects in clinical trials. The lack of correlation between PSP-RS and total sway is most likely explained by the strict inclusion criteria of the PROSPERA study, resulting in a low variance of the PSP-RS at baseline. Interestingly, RMS scores were able to predict total survival in PSP Richardson Syndrome.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/posturography-as-an-objective-measure-of-disease-progression-and-prognostication-in-progressive-supranuclear-palsy/