Additional file 1. Figure S1: Phosphorylated α-synuclein pathology in the anterior olfactory nucleus of a multisystem atrophy case. Example of phosphorylated α-synuclein pathology shown at low and high magnifications depicting glial cytoplasmic inclusions in oligodendrocytes of the anterior olfactory nucleus in the olfactory bulb of an individual with multisystem atrophy (type-P; case #49). Scale bars represent 100µM. Figure S2: LB509-mediated α-synuclein reactivity in the anterior olfactory nucleus. A) Percentage of cases in each group that have a pathology score of 1 or higher. B) Correlation between age and LB509-based α-synuclein pathology scores in the control (HCO and NCO) and COVID19+ groups. C) Distribution of LB509 pathology scores for each group. Filled blue squares are subjects suspected of having incidental LBD; filled dark yellow diamond reflects a subject with mixed pathology. D) Relationship between anti-CD68 scores and LB509-based α-synuclein pathology scores in the AON of all subjects. Significance was determined using Kruskal-Wallis test with Dunn's post-hoc, where ** denotes p≤0.01 and **** denotes p≤0.0001. Abbreviations for disease groups as in Fig. 1. Table S1: Detailed characteristics of all subjects examined at autopsy. Characteristics listed include age (in years); sex (F, female; M, male); diagnostic group (HCO, healthy control; NCO, neurological control; LBD, Lewy body disorders; AD, Alzheimer disease; OND, other neurological disease); pathology diagnosis at autopsy; ventilation; clinical cause of death; number of days in hospital; site of tissue collection; tissue analyzed; post mortem interval (PMI; in hours); hippocampal (hippocamp.) staining; α-synuclein staining in the Substantia nigra (SN) and dorsal motor nucleus of the vagus nerve (DNV). * Indicate cases with an inflammatory condition. # Indicate cases with mixed pathology. Abbreviations: AD, Alzheimer disease; ADNC, Alzheimer disease neuropathologic change. AxBxCx scoring of AD-linked neuropathology in the hippocampus was applied as per Hyman BT et al., 2012 Alzheimer’s Dementia Jan;8(1):1-13; AML, acute myeloid leukemia; DAD, diffuse alveolar disease; ECMO, extracorporeal membrane oxygenation; LBD, Lewy body diseases; DLB, dementia with Lewy bodies; PSP, progressive supranuclear palsy; FTLD-TDP, frontotemporal lobar degeneration-Tar DNA-binding protein; MSA-P, multisystem atrophy-parkinsonian type (P); N, no; NA, not applicable or not available; Y, yes. Table S2: Resources and reagents used in study. Table S3: Detailed results for phosphorylated α-synuclein staining of each case. Abbreviations for disease groups as in Table S1. N, no; Y, yes. Table S4: Detailed results for phosphorylated tau staining of each case. Abbreviations for disease groups as in Table S1. Table S5: Detailed results for amyloid-β peptide staining of each case. Abbreviations for disease groups as in Table S1. AxBxCx scoring of Alzheimer disease-linked neuropathology in the hippocampus was applied as per Hyman BT et al., 2012 Alzheimer’s Dementia Jan;8(1):1-13; NA, not applicable or not available; N, no; Y, yes. Table S6: Detailed results for CD68 staining of each case. Abbreviations for disease groups as in Table S1. Table S7: Detailed results for LB509-based α-synuclein staining of each case. Abbreviations for disease groups as in Table S1.