Japanese longitudinal biomarker study in progressive supranuclear palsy and corticobasal degeneration: Clinical features of the first registered patients and short-term follow-up analysis.

Introduction: Progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) manifest with variable clinical features. We initiated a multicenter prospective registry study-the Japanese Longitudinal Biomarker Study in PSP and CBD-in November 2014 at 45 Japanese institutions to collect clinical information and biological samples to elucidate the natural courses and diagnostic biomarkers of PSP/CBD. Methods: Initial symptoms, clinical features, and scores (Progressive Supranuclear Palsy Rating Scale [PSPRS], Barthel Index, Mini-Mental State Examination, and Frontal Assessment Battery) of patients clinically diagnosed with PSP/corticobasal syndrome (CBS) at the first registration were analyzed. PSPRS score progression in the initial 8 years and predictive factors were examined. Results: As of October 2022, first registration had been conducted for 349 patients-57 with probable/possible Richardson's syndrome (RS), 133 with possible CBS, 41 with overlapping CBS and PSP criteria (RS/CBS group), 20 with PSP subtypes other than RS, and 98 who did not fulfill the PSP or CBS criteria. Among the RS, CBS, and RS/CBS groups, the RS group exhibited the best scores. Initial symptoms of personality change and asymmetric onset were correlated with the total PSPRS score. The average PSPRS score increment by the second registration (n = 116 patients) was 11.8 in all three groups, and progression was correlated with cognitive dysfunction. Seventy patients died during the study period. The 5-year survival rate from onset was approximately 90 %. Conclusion: There were fewer severe clinical features in the RS group than in the CBS group. Cognitive dysfunction may be important in predicting clinical severity and disease progression.