The correlates of hyperechogenicity of the substantia nigra in subjects at risk of dementia with Lewy bodies
Substantia nigra hyperechogenicity (SN+) detected by transcranial sonography (TCS) has been proposed as a risk marker for synucleinopathies, particularly Parkinson's disease. Its role in prodromal dementia with Lewy bodies (DLB) remains insufficiently explored. To examine clinical, cognitive, genetic, EEG, and plasma biomarker differences between SN+ and normal echogenicity (SN-) individuals in a well-characterized at-risk-of-DLB cohort, with additional sex-stratified analyses. A total of 121 participants aged 55-70 years from an at-risk-of-DLB cohort underwent TCS, neurological and neuropsychological assessment, nighttime wrist actigraphy, high-density EEG, genetic testing for APOE allelic variants, and plasma biomarker analysis (NfL, GFAP, pTau181). SN status was defined using laboratory-specific cut-offs. Group differences were assessed using non-parametric statistics with relevant corrections for multiple comparisons and adjustment for age. SN+ status as compared to SN- status was associated with poorer verbal memory performance and altered visuo-constructive performance (driven mostly by males), and significant differences in distinct actigraphy-derived sleep parameters.