Choroid plexus enlargement correlates with periventricular pathology but not with disease activity in radiologically isolated syndrome

Background: Choroid plexus (ChP) enlargement is an emerging radiological biomarker in multiple sclerosis (MS).Objectives: This study aims to assess ChP volume in a large cohort of patients with radiologically isolated syndrome (RIS) versus healthy controls (HC) and explore its relationship with other brain volumes, disease activity, and biological markers.Methods: RIS individuals were included retrospectively and compared with HC. ChPs were automatically segmented using an in-house automated algorithm and manually correctedResults: A total of 124 patients fulfilled the 2023 RIS criteria, and 55 HCs were included. We confirmed that ChPs are enlarged in RIS versus HC (mean (±SD) normalized ChP volume: 17.24 (±4.95) and 11.61 (±3.58), respectively, p < 0.001). Larger ChPs were associated with more periventricular lesions (ρ = 0.26; r2 = 0.27; p = 0.005 for the correlation with lesion volume, and ρ = 0.2; r2 = 0.21; p = 0.002 for the correlation with lesion number) and lower thalamic volume (ρ = -0.38; r2 = 0.44; p < 0.001), but not with lesions in other brain regions. Conversely, ChP volume did not correlate with biological markers. No significant difference in ChP volume was observed between subjects who presented or did not have a clinical event or between those with or without imaging disease activity.Conclusions: This study provides evidence that ChP volume is higher in RIS and is associated with measures reflecting periventricular pathology but does not correlate with biological, radiological, or clinical markers of disease activity.