0912 Striatal atrophy and clinical correlates in REM sleep behavior disorder

Introduction Idiopathic/isolated REM sleep behavior disorder (iRBD) is regarded as the most specific prodromal stage of ⍺-synucleinopathies including Parkinson’s disease (PD). Striatal dopamine dysfunction is a pathological hallmark in PD, which has been similarly reported in iRBD as a sensitive marker for detecting early ⍺-synucleinopathies. In contrary, although there is a broad consensus that patients with PD have striatal volumes reduction, studies in iRBD are relatively scarce and inconsistent. In this study, we aim to investigate the difference of striatal nuclei volumes between iRBD and controls and their correlation with clinical presentations. Methods Altogether 105 patients (mean age=68.19, male 76.2%) with polysomnography-confirmed iRBD and 85 age and sex comparable controls (mean age=66.74, male 64.7%) underwent 3-tesla MRI and clinical assessments. FreeSurfer automatic segmentation pipelines measured the size of bilateral striatal nuclei including caudate, putamen, pallidum and accumbens area. The comparisons of the volume of individual striatal nucleus were made between iRBD and controls with age, sex, handness, and total intracranial volume as covariates. Correlations were performed to investigate the association between striatal nuclei volume and clinical domains in motor (Unified Parkinson’s Disease Rating Scale, Part III), cognitive (Montreal Cognitive Assessment, MoCA), visual (pareidolia), autonomic function (Scales for Outcomes in Parkinson’s Disease - Autonomic Dysfunction, SCOPA-AUT) and mood symptoms (Hospital Anxiety and Depression Scale). Results There were smaller volumes in the bilateral putamen (t=-2.13/-2.32, p=0.03/0.02, left/right side respectively) and accumbens area (t=-2.58/-2.07, p=0.01/0.04, left/right side respectively) in iRBD comparing to controls. In addition, MoCA score was significantly positively correlated with the volumes of bilateral putamen (r=0.212/0.213, p=0.032/0.033), while pareidolia score was significantly negatively correlated with volumes of bilateral putamen (r=-0.205/-0.233, p=0.039/0.018,) and accumbens area (r=-0.249/-0.279, p=0.012/0.004, left/right respectively). The SCOPA-AUT score was significantly negatively correlated with volumes of the left putamen (r=-0.286, p=0.014) and the left accumbens area (r=-0.245, p=0.037). No other correlations with mood and motor features were found. Conclusion In this large case-control study, PD-like striatal atrophy was already present in patients with iRBD, which were significantly associated with worse cognitive performance, visual and autonomic dysfunction. Support (if any) This study was supported by Hong Kong Health and Medical Research Fund, 08191416.