Cognitive Performance in Parkinson's Spectrum Disorders: a comparative study of patients with Parkinson's Disease, Parkinson's Disease Dementia, Dementia With Lewy Bodies, Progressive Supranuclear Palsy, and Corticobasal Syndrome.

The Parkinson's spectrum encompasses Parkinson's disease (PD), PD dementia (PDD), dementia with Lewy bodies (DLB), progressive supranuclear palsy (PSP), and corticobasal syndrome (CBS). Clinical diagnosis mainly relies on progression over time and neuroimaging, biomarkers, and neurological observations, aided by neuropsychological assessment. Neuropsychological profiles and differences within the Parkinson's spectrum have been understudied. This retrospective study analyzed mean performance and proportions of impairment of neuropsychological assessments of 212 patients in the Parkinson's spectrum at an academic outpatient memory clinic. Patients with PD scored significantly higher than the other patient groups on most tests. The other patient groups showed limited significant differences from one another. The letter fluency test was most effective in distinguishing PD from the other disorders. The auditory verbal learning test was suitable to distinguish PDD and DLB from the other disorders. Results indicate considerable overlap in cognitive profiles across Parkinson's spectrum disorders, suggesting neuropsychological assessment is valuable for assessing cognitive function, guiding post-diagnostic support, and monitoring progression, rather than differential diagnosis.