Objective: The aim of the current study was to determine the proportion of patients, initially classified as having prodromal Parkinson’s disease (pPD), phenoconverted to manifest neurodegenerative disease at follow-up (FU) after 2-5 years and assess the spectrum of final diagnoses in 2 cohorts recruited via gastrointestinal symptoms – PARCAS [1] and idiopathic REM Sleep Behavior Disorder (iRBD) – PDBIOM [2].

Background: Updated MDS research criteria for pPD [3] are the gold standard for identification of PD before the onset of unequivocal parkinsonism. Enriched cohorts composed of patients with high-risk prodromal non-motor symptoms such as iRBD are of particular interest.

Method: Patients from 2 research cohorts were deeply phenotyped according to the updated MDS research criteria for pPD both at baseline and FU examination. The final clinical diagnosis in case of phenoconversion to overt motor disease was made by a movement disorders specialist, based on standard diagnostic criteria.

Results: 30/78 subjects (17 initially classified as pPD) included in the PDBIOM cohort and 67/162 subjects (12 initially classified as pPD) included in the PARCAS cohort underwent FU examination to this date. Of all subjects 6 phenoconverted to manifest neurodegenerative disease – 5 cases to PD, 1 case to corticobasal syndrome (CBS). All 5 PD patients were previously correctly identified as probable pPD based on the updated MDS research criteria (probability >80%) and 1 CBS patient was previously identified as possible pPD (probability >50%, specifically 69%).

Conclusion: Updated MDS research criteria for pPD serve as a sensitive screening tool for prediction of later onset of manifest PD. However, their specificity for prodromal PD alone (or synucleinopathies in general) seems questionable as 1 CBS case (tauopathy) was also identified, indicating a greater ability to detect neurodegenerative parkinsonism in prodromal stage than originally intended, which may pose a challenge for a prodromal diagnosis-specific inclusion of patients in future clinical trials.

Acknowledgements: This work was supported by the Slovak Research and Development Agency under contract no. APVV-22-0279 and by the Slovak Scientific Grant Agency under contract no. VEGA 1/0712/22.

References: [1] Skorvanek M, Ladomirjakova Z, Han V, et al. Prevalence of prodromal Parkinson’s disease as defined by MDS research criteria among elderly patients undergoing colonoscopy. J Parkinson Dis 2017; 7: 481-489.
[2] Kulcsarova K, Ventosa JR, Feketeova E, et al. Comparison in detection of prodromal Parkinson’s disease patients using original and updated MDS research criteria in two independent cohorts. Parkinsonism Relat Disord 2021; 87: 48-55.
[3] Heinzel S, Berg D, Gasser T, et al. Update of the MDS research criteria for prodromal Parkinson´s disease. Mov Disord 2019; 34: 1464-1470.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/beyond-parkinsons-disease-and-synucleinopathies-unexpected-identification-of-prodromal-corticobasal-syndrome-by-the-updated-mds-research-criteria-for-prodromal-pd/