Our study, performed in a well-defined CCSVI population, showed that there was a significant difference among IJVS, CVSS, and CVSS combined with IJVS groups in terms of symptoms, risk factors, and inflammatory state (Table 1). CVSS group tended to have headaches and severe papilledema due to a higher prevalence of IH, presented at a younger age, and frequently combined with risk factors, such as PC deficiency, primary thrombocythemia, overweight, and hyperhomocysteinemia. Higher levels of NLR, RDW, and CRP were also observed in the CVSS group. Moreover, most patients with CCVSI, either intracranial cause or extracranial cause, acquired good clinical outcome during our follow-up (Fig. 5). NLR, PLR, and IL-6 were found to be the independent prognostic factors for outcomes (Table 3). We further constructed a reliable nomogram model for patients with CCSVI to predict long-term prognosis (Fig. 8).
Our study is the first evaluating the possible association between inflammation and CCSVI. In the last decade, a number of studies were carried out to explain the underlying mechanism of CCSVI (Fig. 9),2, 24, 25 however, the majority of previous studies are exclusively enrolled MS population to explore the causative relationship between CCSVI and MS, instead of regarding CCSVI as an independent disease entity. Besides, few case-control studies observed CCSVI was also highly prevalent in the non-MS population, and not unique to MS,3, 4, 26 then leading to a lively discussion on whether CCSVI was anatomical variants of a complex vascular system or pathological process.27–30
Intriguingly, our enrolled patients, without any previous or current evidence of MS, had elevated NLR, PLR, RDW, IL-6, and CRP, which may be attributed to CCSVI itself rather than MS. Thus, we assumed CCSVI as an independent disease entity, which closely related to the chronic inflammatory process. Firstly, CCSVI may cause the mechanical effect of engorgement and reflux on the brain tissue,10, 31 which would increase cerebral venous pressure (CVP), decrease transmural pressure (TP), and then lead to perivenous edema and disruption of BBB integrity.2 CVP could also cause decreased cerebral blood flow (CBF), cerebral blood volume (CBV) and elevated mean transit time (MTT).8, 24, 32, 33 Secondly, the suboptimal drainage could result in iron deposition within the brain parenchyma with the potential of initiating local inflammatory responses.6, 34, 35 Furthermore, CCSVI was also associated with the autonomic neurological system (ANS) dysfunction.25, 36
As reviewed by Sternberg, Sympathetic ANS has widespread α- and β-adrenergic receptors on endothelial cells and inflammatory cells. ANS dysfunction could not only weaken the modulation of the cardiovascular system to adapt demands of cerebral cortical activity resulting in decreased CBF and chronic hypoxia, trigger for venous remodeling,37–39 but also regulate the immune system to activate cellular inflammation, adhesion and migration.36 Besides, the role of the hyper-coagulation state in inflammatory process should not be overlooked.7 We found hyper-coagulation state (e.g., PC deficiency, primary thrombocythemia, overweight) and increased inflammatory biomarkers (e.g., NLR, PLR, CRP) were more likely in CVSS group. Last but not least, we thought CCSVI-induced inflammation was a well-balanced state of pro-inflammatory and anti-inflammatory factors. Our correlation analysis between inflammatory cells and inflammatory cytokines indicated that NLR and PLR were positively associated with IL-6. Patients with higher NLR, PLR, IL-6, or CRP had poorer clinical outcomes. Thus, we postulated that when CCSVI-induced inflammatory state tilted toward the pro-inflammatory side, patients would suffer more severe symptoms and poor prognosis.
There are several limitations in our study. There is no established diagnostic criteria and imaging modality, either non-invasive or invasive, that can serve as the “gold standard” for the detection of CCSVI.40, 41 The 'Zamboni criteria' only focused on evaluating the major venous drainage pathway, such as IJV, vertebral vein (VV), CVS, and deep cerebral vein,1 while overlooked the presumable risk factors,20 degrees of collateral circulation compensation and inflammatory biomarkers.7 We suggested that future studies could combine clinical and imaging features to define CCSVI. Additionally, we established a nomogram prognostic scoring model with high predictive value. A higher score of the nomogram, calculated from a sum of points from each variable, would be associated with unfavorable outcomes. However, this nomogram was only tested by internal validation by bootstrap resampling and calibration plot. Further external validation was needed in the future.