It has been proposed that multiple sclerosis (MS) is caused by chronic cerebrospinal venous insufficiency (CCSVI), a term that describes ultrasound-detectable abnormalities in the anatomy and flow of intra- and extracerebral veins. This meta-analysis was conducted of studies published on MEDLINE and EMBASE that reported the frequency of CCSVI among patients with and without MS. Eight eligible studies were identified; all included healthy controls, and four of them also included a control group of patients with neurologic diseases other than MS. CCSVI was more frequent among patients with MS than among the healthy controls (OR: 13.5; 95% CI: 2.6-71.4) but there was extensive unexplained heterogeneity among the studies. The association remained significant in the most conservative sensitivity analysis (OR: 3.7; 95% CI: 1.2-11.0). Although CCSVI was also more frequent among patients with MS than among controls with other neurologic diseases (OR: 32.5; 95% CI: 0.6–1775.7), the association was not statistically significant and the 95% CI was wide. The authors concluded that these findings reveal a positive association between CCSVI and MS but that poor reporting of the success of blinding and marked heterogeneity among the studies preclude definitive conclusions. CMAJ. 2011 Oct 3. PMID: 21969411.
