Choroid plexus enlargement and Kappa light chains index reflect distinct pathophysiological processes in Multiple...

Multiple sclerosis (MS) is a complex neuroinflammatory and neurodegenerative disorder. Choroids plexus (CP) volume and the Kappa free light chain index (K-index) are emerging as relevant biomarkers in the disease. However, the relationship between these markers remains unclear.

To investigate the association between CP volume and K-index in people with MS (PwMS). As part of the secondary objectives, we explored potential correlations between CP volume or K-index and disease duration, CSF cellularity and different brain volumetric parameters.

In this multicentric, retrospective study, adult PwMS were recruited from three French tertiary hospitals between 2018 and 2023. Subjects underwent 3DT1 gradient echo brain magnetic resonance imaging sequence and lumbar puncture within 6 months from one another. CP volume was measured using an automated segmentation algorithm and normalized by total intracranial volume. The K-index was calculated from cerebrospinal fluid and serum free light chains levels obtained via a turbidimetric analyser. Statistical analysis including partial correlations adjusted for age, gender, disease duration, and ventricular volume were performed to assess the relationship between CP and K-index, as well as their associations with other clinical parameters. We applied false discovery rate correction for multiple comparisons to all p-values of correlation tests.

We've included 82 adult PwMS ((68 with relapsing-remitting MS and 14 with primary progressive MS in the study. No significant correlation was observed between CP volume and K-index (r = -0.016, p = 0.89). Larger CP volume correlated with increased ventricular volume, older age and longer disease duration. Unlike CP volume, K-index was not associated with structural brain alterations related to the disease severity but was inversely associated with age, with younger patients showing higher values.

Our results suggest that there is no correlation between CP volume and K-index in PwMS, suggesting that these biomarkers likely reflect distinct pathophysiological mechanisms.