Enlarged choroid plexus related to iron rim lesions and deep gray matter atrophy in relapsing-remitting multiple sclerosis

Choroid plexus (CP) is considered to be linked to inflammation of multiple sclerosis (MS), but its connection with markers of inflammation in vivo in MS is unclear, the markers such as lesions load and brain atrophy, particularly the white matter lesions (WMLs) edge surrounded by an iron rim, termed as iron rim lesions (IRLs).To investigate the association between CP volume and brain lesions load, especially IRLs load and atrophy in MS, and its relationship with clinical characteristics.3.0 T brain MRI images were acquired from 99 relapsing-remitting MS (RRMS) and 60 healthy controls (HCs) to obtain the volumes of CP, whole brain and lesions. Volumes were expressed as a ratio of intracranial volume. Expanded Disability Status Scale (EDSS), Montreal Cognitive Assessment (MoCA) and Symbol Digit Modalities Test (SDMT) were used to assess the severity of disability and cognitive function. Student's t-test and Multivariable regression analyses were performed to evaluate the difference of CP volumes between RRMS and HC and the association between CP volume and lesions load, brain volumes and clinical scale scores in RRMS.CP volume was 30% larger in patients with RRMS than HCs (p < 0.001) and was 20% larger in patients with IRLs than those without IRLs (p = 0.007). Moreover, the larger CP volume was related to greater WMLs volume in the whole RRMS (r = 0.46, p < 0.001). Further analysis in patients with IRLs showed a positive correlation between CP volume and WMLs volume (r = 0.45, p = 0.003), and IRLs volume (r = 0.51, p < 0.001). Meanwhile, enlarged CP was related to lower volumes in the whole brain (r = -0.30, p = 0.006), deep gray matter (r = -0.51, p < 0.001) and most regional deep gray matter nuclei (except amygdala), but no correlation with cortical lesions or cortex volume (both p > 0.05). In addition, CP volume was significantly higher in patients with cognitive impairment than those with cognitive preservation by MoCA scores (p = 0.011); the larger CP volume was associated with higher EDSS scores (r = 0.25, p = 0.014) and lower SDMT Z scores in RRMS (r = -0.26, p = 0.014).The enlargement of CP in RRMS had close correlations with inflammatory lesions, especially IRLs and deep gray matter atrophy, but not the cortex. Meanwhile, the larger CP volume was associated with higher disability and lower cognitive scores. CP volume may be a surrogate imaging marker for MS disease activity.