Characteristics and progression of cognitive deficits in progressive supranuclear palsy vs. multiple system atrophy and Parkinson's disease

Cognitive impairment is frequent in progressive supranuclear palsy (PSP) and less common in multiple system atrophy (MSA), but characteristics and progression compared with Parkinson's disease (PD) need to be properly defined. We evaluated 35 PSP with Richardson's syndrome (PSP-RS), 30 MSA as well as 65 age-, sex-, and education-matched PD with an extensive clinical and neuropsychological assessment, allowing Level II cognitive diagnosis. Eighteen PSP, 12 MSA and 30 PD had a second evaluation between 12 and 18 months (mean 15 months) after the first assessment. PSP performance at Montreal Cognitive Assessment (MoCA), verbal fluencies (phonemic and semantic tasks), Stroop test (Error and Time), Digit Span Sequencing (DSS), incomplete letters of Visual Object and Space Perception (VOSP) and Benton's Judgment of Line Orientation (JLO) performance were significantly poorer at baseline compared to PD and MSA. Executive, language and visuospatial abilities declined longitudinally in PSP, but not in PD and MSA. After 1.5 year, 16% of PSP converted to dementia. Our study provides evidence that cognitive progression is more severe and rapid in PSP-RS than PD and MSA. Further, we observed that MoCA, verbal fluency (particularly semantic), DSS and Benton's JLO are valuable tests to detect cognitive progression in PSP-RS and may be proposed as possible biomarker to assess efficacy of disease modification strategies.