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COVID-19 has highlighted the need for remote cognitive testing, but the reliability and validity of virtual cognitive testing in Parkinson disease (PD) is unknown. Therefore, we assessed PD participants enrolled in an observational, cognition-focused study with an extensive cognitive battery completed both in-person and via video conference close in time. Data for 35 PD participants with normal cognition to mild dementia were analyzed. Only one test (semantic verbal fluency) demonstrated a difference in score by administration type, with a significantly better score virtually. Only three tests demonstrated good reliability for in-person versus virtual testing, but reliability values for visit 1 versus visit 2 were similarly low overall. Trail Making Test B was successfully administered virtually to only 18 participants due to technical issues. Virtual and in-person cognitive testing generate similar scores at the group level, but with poor to moderate reliability for most tests. Mode of test administration, learning effects, and technical difficulties explained little of the low test–retest reliability, indicating possible significant short-term variability in cognitive performance in PD in general, which has implications for clinical care and research. In-person cognitive testing with a neuropsychologist remains the gold standard, and it remains to be determined if virtual cognitive testing is feasible in PD.

Objective The Parkinson's Progression Markers Initiative (PPMI) is an observational, international study designed to establish biomarker‐defined cohorts and identify clinical, imaging, genetic, and biospecimen Parkinson's disease (PD) progression markers to accelerate disease‐modifying therapeutic trials. Methods A total of 423 untreated PD, 196 Healthy Control (HC) and 64 SWEDD (scans without evidence of dopaminergic deficit) subjects were enrolled at 24 sites. To enroll PD subjects as early as possible following diagnosis, subjects were eligible with only asymmetric bradykinesia or tremor plus a dopamine transporter (DAT) binding deficit on SPECT imaging. Acquisition of data was standardized as detailed at www.ppmi-info.org. Results Approximately 9% of enrolled subjects had a single PD sign at baseline. DAT imaging excluded 16% of potential PD subjects with SWEDD. The total MDS‐UPDRS for PD was 32.4 compared to 4.6 for HC and 28.2 for SWEDD. On average, PD subjects demonstrated 45% and 68% reduction in mean striatal and contralateral putamen Specific Binding Ratios (SBR), respectively. Cerebrospinal fluid (CSF) was acquired from >97% of all subjects. CSF (PD/HC/SWEDD pg/mL) α‐synuclein (1845/2204/2141) was reduced in PD vs HC or SWEDD (P < 0.03). Similarly, t‐tau (45/53) and p‐tau (16/18) were reduced in PD versus HC (P < 0.01), Interpretation PPMI has detailed the biomarker signature for an early PD cohort defined by clinical features and imaging biomarkers. This strategy provides the framework to establish biomarker cohorts and to define longitudinal progression biomarkers to support future PD treatment trials.

The impact of executive dysfunction on performance of basic activities of daily living (BADLs) and instrumental activities of daily living (IADLs) in patients with Parkinson’s disease (PD) has been established (Cahn et al., 1998). Poor performance on cognitive measures of executive functioning indicates difficulty with complex, goal-directed behaviors which may lead to difficulty with completing BADLs/IADLs (Bell-McGinty et al., 2002). This dissertation examined the association between change in performance on measures of executive functioning and change in IADLs in an archival sample of 81 individuals with PD classified by consensus diagnosis as normal cognition at baseline. We specifically explored executive abilities to evaluate change in which specific measure(s) of executive functioning best predicted change in informant-reported IADLs across one year. We found that change in performance on the Trail Making Test-B (TMT-B) is the strongest predictor of change in informant-reported functional abilities in a nondemented PD cohort ( p<.05). Exploratory analysis of a cohort comprised of individuals with PD classified as normal cognition at baseline and one-year follow-up revealed that change in performance on the Symbol Digit Modalities Test (SDMT) was a significant predictor of change in daily functioning ( p<.05). These findings have implications for assessing change in IADLs in settings where direct observation and caregiver report are not available. Additionally, accurate predictions of decline in performance of daily functioning may improve the direction and precision of care for individuals with PD.