Enlarged choroid plexus in multiple sclerosis is associated with increased lesion load and atrophy in white matter but not gray matter atrophy

Choroid plexus volume changes in multiple sclerosis: insights from a systematic review and meta-analysis of magnetic resonance imaging studies

PURPOSE

Multiple sclerosis (MS) is a chronic autoimmune disease characterized by the destruction of the myelin sheath within the central nervous system. The etiology of MS involves a complex interplay of genetic, environmental, and immunological factors. Recent studies indicated the potential role of the choroid plexus (CP) in the pathogenesis and progression of MS. This systematic review aims to assess existing research on the volume alterations of the CP in MS patients compared to the normal population.

METHODS

A comprehensive search was conducted across databases including PubMed, Embase, Scopus, and Web of Science up to June 2024. Data from the included studies were synthesized using a meta-analytical approach with a random-effects model, assessing heterogeneity with the I2 and Tau-squared indices.

RESULTS

We included 17 studies in this systematic review. The meta-analysis, which included data from eight studies reporting CP volume relative to TIV, found a statistically significant increase in CP volume in MS patients compared to healthy controls (HCs). The SMD was 0.77 (95% CI: 0.61 to 0.93), indicating a large effect size. This analysis showed no heterogeneity (I² = 0%). A separate meta-analysis was conducted using five studies that reported CP volume as normalized volume, resulting in an SMD of 0.63 (95% CI: 0.2-1.06).

CONCLUSION

This study demonstrates an increase in CP volume among MS patients compared to HCs, implying the potential involvement of CP in MS pathogenesis and/or progression. These results show that CP might serve as a radiological indicator in the diagnosis and prognosis of MS.

Choroid plexus enlargement is associated with future periventricular neurodegeneration in multiple sclerosis

BACKGROUND

The choroid plexus (CP), located within the ventricles of the brain and the primary producer of cerebrospinal fluid, has been shown to be enlarged in patients with multiple sclerosis (MS) and linked to periventricular remyelination failure. Atrophied T2-lesion volume (aT2-LV), a promising neurodegenerative imaging marker in progressive MS (PMS), reflects the volume of periventricular lesions subsumed into cerebrospinal fluid over the follow-up.

METHODS

In a cohort of 143 people with relapsing-remitting MS (RRMS) and 53 with PMS, we used 3T magnetic resonance imaging (MRI) to quantify CP volume (CPV) at baseline and aT2-LV over an average of 5.4 years of follow-up. Partial correlations, adjusting for age and sex, and linear regression analyses were used to assess the relationships between imaging measures.

RESULTS

In both cohorts, CPV was associated with aT2-LV in both the RRMS group (r = 0.329, p < 0.001) as well as the PMS group (r = 0.522, p < 0.001). In regression analyses predicting aT2-LV, ventricular volume (final adjusted R2 = 0.407, p < 0.001) explained additional variance beyond age, sex, and T2-lesion volume in the RRMS group while CPV (final adjusted R2 = 0.446, p = 0.009) was retained in the PMS group.

CONCLUSION

Findings from this study suggest that the CP enlargement is associated with future neurodegeneration, with a particularly relevant role in PMS.

Continuous diffuse brain atrophy independent of relapse as a hallmark of multiple sclerosis beginning from relapsing-remitting stage

BACKGROUND

Neurodegenerative changes are observed in relapsing-remitting multiple sclerosis (RRMS) and are prominent in secondary progressive MS (SPMS). However, whether neurodegenerative changes accelerate and are altered after the transition into SPMS or in the presence of relapses remains uncertain.

METHODS

In this study, 73 patients with MS (seven with relapsing RRMS, 56 with relapse-free RRMS, and 10 with relapse-free SPMS) were evaluated for brain segmental volume changes over a 2-year follow-up period. Volume change was calculated using a within-subject unbiased longitudinal image analysis model.

RESULTS

The rates of brain volume change in the 11 brain regions evaluated were relatively similar among different brain regions. Moreover, they were similar among the relapsing RRMS, relapse-free RRMS, and SPMS groups, even after adjusting for age.

CONCLUSIONS

The relatively constant brain segmental atrophy rate throughout the disease course, regardless of relapse episodes, suggests that RRMS and SPMS are continuous, uniform, and silent progressing brain atrophy diseases on a spectrum.

The Time Trajectory of Choroid Plexus Enlargement in Multiple Sclerosis

Choroid plexus (CP) can be seen as a watchtower of the central nervous system (CNS) that actively regulates CNS homeostasis. A growing body of literature suggests that CP alterations are involved in the pathogenesis of multiple sclerosis (MS) but the underlying mechanisms remain elusive. CPs are enlarged and inflamed in relapsing-remitting (RRMS) but also in clinically isolated syndrome (CIS) and radiologically isolated syndrome (RIS) stages, far beyond MS diagnosis. Increases in the choroid plexus/total intracranial volume (CP/TIV) ratio have been robustly associated with increased lesion load, higher translocator protein (TSPO) uptake in normal-appearing white matter (NAWM) and thalami, as well as with higher annual relapse rate and disability progression in highly active RRMS individuals, but not in progressive MS. The CP/TIV ratio has only slightly been correlated with magnetic resonance imaging (MRI) findings (cortical or whole brain atrophy) and clinical outcomes (EDSS score) in progressive MS. Therefore, we suggest that plexus volumetric assessments should be mainly applied to the early disease stages of MS, whereas it should be taken into consideration with caution in progressive MS. In this review, we attempt to clarify the pathological significance of the temporal CP volume (CPV) changes in MS and highlight the pitfalls and limitations of CP volumetric analysis.

Basal Ganglia Atrophy and Impaired Cognitive Processing Speed in Multiple Sclerosis

Impaired cognitive processing speed is among the important higher brain dysfunctions in multiple sclerosis (MS). However, the exact structural mechanisms of the dysfunction remain uncertain. This study aimed to identify the brain regions associated with the impaired cognitive processing speed in MS by comparing the cognitive processing speed, measured using the Cognitive Processing Speed Test (CogEval) z-score, and brain regional volumetric data. Altogether, 80 patients with MS (64 with relapsing-remitting MS [RRMS] and 16 with secondary progressive MS [SPMS]) were enrolled. Consequently, CogEval z-scores were worse in patients with SPMS than in those with RRMS (p=0.001). In the univariate correlation analyses, significant correlations with CogEval z-score were suggested in the MS lesion volume (p<0.001; Spearman's rank correlation test) and atrophies in the cerebral cortex (p=0.031), cerebral white matter (p=0.013), corpus callosum (p=0.001), thalamus (p=0.001), and putamen (p<0.001). Multiple linear regression analysis revealed that putamen atrophy was significantly associated with CogEval z-score (p=0.038) independent of volume in other brain regions, while thalamic atrophy was not (p=0.79). Univariate correlation analyses were further performed in each of RRMS and SPMS. None of the evaluated volumetric data indicated a significant correlation with the CogEval z-score in RRMS. Meanwhile, atrophies in the cerebral white matter (p=0.008), corpus callosum (p=0.002), putamen (p=0.011), and pallidum (p=0.017) demonstrated significant correlations with CogEval z-score in SPMS. In summary, the putamen could be an important region of atrophy contributing to the impaired cognitive speed in MS, especially in the later disease stages after a transition to SPMS.