Insular monoaminergic deficits in prodromal α‐synucleinopathies

Abstract

Abstract Methods This study assessed data from two cohorts of patients with alpha‐synucleinopathies (University of Brescia and University of Rome Tor‐Vergata cohorts). Consecutive participants with video‐polysomnography‐confirmed iRBD, Parkinson's disease (PD), dementia with Lewy bodies (DLB) and controls underwent neurological, clinical and 123I‐FP‐CIT SPECT imaging assessments. Individuals with iRBD were longitudinally monitored to collect clinical phenoconversion to PD or DLB. The main outcome was to identify whole brain 123 I‐FP‐CIT SPECT measures reflecting monoaminergic deficits in each clinical group as compared to controls. Results The cohort (n = 184) included 45 patients with iRBD, 47 PD, 42 DLB and 50 age‐matched controls. Individuals with iRBD were categorized as RBD‐DAT− (n = 32) and RBD‐DAT+ (n = 13), according to nigrostriatal assessment used in clinical practice. Compared to controls, RBD‐DAT− showed an early involvement of the left insula, which increased in RBD‐DAT+, and was present in patients with Parkinson's disease and dementia with Lewy bodies. Longitudinal cox regression analyses revealed a higher risk of phenoconversion in individuals with iRBD and insular monoaminergic deficits [HR = 3.387; CI 95%: 1.18–10.27]. Interpretation In this study, altered insular monoaminergic binding in iRBD was associated with phenoconversion to DLB or PD. These findings may provide a helpful stratification approach for future pharmacological or non‐pharmacological interventions.