Statistical Models of Parkinson's Disease Progression: Predictive Validity in a 3-Year Follow-up.

BACKGROUND: The rate of Parkinson's disease (PD) progression varies widely between patients. Current knowledge does not allow to accurately predict the evolution of symptoms in a given individual over time. OBJECTIVES: To develop regression-based models of PD progression and to explore its predictive value in a three-year follow-up. METHODS: At baseline, 300 consecutive PD patients were assessed using the Unified Parkinson's Disease Rating Scale (UPDRS) - subscales II and III, Hoehn & Yahr (H&Y) and Schwab and England Independence Scale (S&E); and the Freezing of Gait Questionnaire (FOG-Q). UPDRS-III and H&Y were applied in OFF and ON medication conditions. An axial index was derived from the UPDRS-III. Based on multiple linear regression coefficients, algorithms were developed to adjust test scores to the characteristics of each individual. Sixty-eight patients were reevaluated three years later. RESULTS: In the construction of the models, disease duration, age ≥70, age at disease onset ≥55, tremor as the first symptom alone, and medication description explained between 35% (UPDRS-III in ON) and 57% (axial index in ON) of the variance of test scores. The predictive r2 of the models in a 10-fold cross-validation ranged between 33% (UPDRS-III in ON) and 55% (axial index in ON and S&E in OFF). All measures, except UPDRS-III OFF, H&Y ON, and S&E ON, had moderate/good absolute agreement (intraclass correlation coefficient between 0.60 and 0.72) between baseline and follow-up. CONCLUSIONS: A cross-sectional assessment of a PD population allowed the development of models of disease progression, whose predictive value was validated on a three-year longitudinal study.

Appendectomy may delay Parkinson's disease Onset.

BACKGROUND: Alpha-synuclein (α-Syn) is particularly abundant in the vermiform appendix, which makes this structure an anatomical candidate for the initiation of Parkinson's disease (PD) pathology. We hypothesized that history of appendectomy might affect PD clinical onset. METHODS: A total of 295 PD patients enrolled in a comprehensive observational study were asked about past history of appendectomy. Cox's regression, with a time-dependent covariate, explored the effects of appendectomy on age at PD onset. RESULTS: Thirty-four patients (11.5%) had appendectomy before PD onset. There was no significant effect of appendectomy on age at PD onset for the entire cohort (P = 0.153). However, among patients with late onset (≥55 years), we found evidence that those with past appendectomy had more years of life without PD symptoms than patients without appendectomy (P = 0.040). No association was found for the young-onset group (P = 0.663). CONCLUSIONS: An apparent relationship was observed between appendectomy and PD onset in the late PD cohort.

Task-specific contribution of the human striatum to perceptual-motor skill learning.

Acquisition of new perceptual-motor skills depends on multiple brain areas, including the striatum. However, the specific contribution of each structure to this type of learning is still poorly understood. Focusing on the striatum, we proposed (a) to replicate the finding of impaired rotary pursuit (RP) and preserved mirror tracing (MT) in Huntington's disease (HD); and (b) to further explore this putative learning dissociation with other human models of striatal dysfunction (i.e., Parkinson's disease and focal vascular damage) and two new paradigms (i.e., Geometric Figures, GF, and Control Stick, CS) of skill learning. Regardless of the etiology, participants with damage to the striatum showed impaired learning of visuomotor tracking skills (i.e., RP and GF), whereas the ability to learn skills that require motor adaptation (i.e., MT and CS) was not affected. These results suggest a task-specific involvement of the striatum in the early stages of skill learning.