Objective: Investigating brain structure and cognition in healthy individuals with positive Parkinson’s disease (PD) risk markers (hyposmia, increased hyperechogenic area of the substantia nigra).

Background: Hyposmia and an enlarged substantia nigra hyperechogenicity upon transcranial sonography are associated with an increased risk for PD in healthy individuals. It is assumed that a proportion of healthy individuals exhibiting these risk markers develop manifest PD later in life. It is unclear so far to which extent these risk markers are accompanied by changes in brain structure or cognitive functions.

Methods: In an embedded case-control test design 29 individuals with possible prodromal PD (Brief Smell Identification Test ≤15th percentile and/or hyperechogenic area ≥0.25 cm2) and 28 controls with normal smell function and unremarkable transcranial sonography results were selected from an initial cohort of 621 persons. A cognitive test battery and the diffusion tensor imaging based indices mean diffusivity (MD) and fractional anisotropy (FA) were used to test for differences between prodromal PD and the control group.

Results: In contrast to controls, the PD risk group showed deficits in verbal memory and verbal fluency tasks, whereas attention, cognitive control and measures of impulsivity were unaffected. Concerning white matter microstructure, individuals with prodromal PD revealed increased MD values in the corticospinal tract, fornix, posterior thalamus, and the fasciculus longitudinalis inferior. MD values in these areas correlated significantly with hyposmia and substantia nigra hyperechogenicity. Voxel-wise testing of FA values did not show any significant differences between groups.

Conclusions: Our data provide first evidence that individuals with possible prodromal PD show signs of structural changes including motor and limbic areas. For these subjects subtle impairments in focused cognitive domains were also observed. The potential value of these results – getting a better prediction for being affected by prodromal PD – has to be evaluated in future longitudinal studies.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/changes-of-brain-structure-and-cognition-in-individuals-with-possible-prodromal-parkinsons-disease/