Lewy body disease (LBD) is a neurodegenerative disorder that causes cognitive and behavioral problems. However, it is difficult to diagnose, and its pathophysiology is still not fully understood. The usual diagnostic criteria for LBD have excellent specificity but poor sensitivity. In particular, we lack paraclinical tests that can make a significant contribution. LBD patients may exhibit abnormalities in brain activity dynamics, which can be detected by EEG and may be linked to neuronal dysfunctions specific to the disease. The objective of this study is twofold: first, to assess the validity of this observation, that is, to confirm that the observed phenomenon is indeed linked to the pathophysiology of LBD, and second, to clarify the nature of these abnormalities by exploring the brain dynamics of LBD patients in greater detail.

Inclusion Criteria:

• Adult subjects (≥18 years old).
• Subject who participated in the Alpha-Lewy-MA cohort and underwent RT-QuIC analysis.
• Subject who underwent a standard EEG examination at HUS between January 1, 2012, and January 1, 2020.

Exclusion Criteria:

- Subject who expressed opposition to participating in the study.

Adult subjects (≥18 years old) who participated in the Alpha-Lewy-MA cohort and underwent RT-QuIC analysis and underwent a standard EEG examination at HUS between January 1, 2012, and January 1, 2020.