According to a review of published studies in the Canadian Medical Association Journal (CMAJ) chronic cerebrospinal venous insufficiency (CCSVI) appears to be more prevalent in people with multiple sclerosis than in those without, however, more high-quality studies have to be carried out in order to make definite conclusions.
In 2009 Dr. Zamboni and his team defined CCSVI as ultrasound-detectable abnormalities in the anatomy and blood flow in the veins draining blood from the brain and back. He discovered that CCSVI was a lot more prevalent in people with multiple sclerosis (MS) than in those without the condition and suggested that CCSVI could be the cause for MS, a degenerative disease of the central nervous system.
CCSVI’s involvement in MS is controversial with some researchers unable of repeating Zamboni’s findings. Canadian researchers from St. Michael’s Hospital at the University of Toronto, the Sunnybrook Health Sciences Centre in Toronto and the University of Calgary in Alberta decided to carry out a meta-analysis of studies, i.e. they combined published study results in the most objective and unbiased manner possible, in which they compared the frequency of CCSVI in those patients suffering from MS and those without.
The new meta-analysis included eight different studies of various quality levels conducted in Germany, Jordan, Italy, and the United States. Because many of these studies were small and did not report the training levels of those conducting the ultrasounds, none of the studies actually revealed whether or how many of those conducting the ultrasound knew if the patient was suffering from MS or not.
The researchers discovered immense variations regarding the frequency of CCSVI in MS patients ranging from 0% to 100% in the case of Zamboni’s study; the same variations were observed in the degree to which CCSVI was linked to multiple sclerosis. While some studies revealed a higher frequency in MS patients compared with those not suffering from the condition, other studies showed a comparative frequency between the two groups although when combined statistically, researchers found that CCSVI was more frequent in those suffering from MS compared with those who were not.
Dr. Andreas Laupacis, Li Ka Shing Knowledge Institute of St. Michael’s Hospital in Toronto and his co-authors write:
“We found a strong and statistically significant association between chronic cerebrospinal venous insufficiency and multiple sclerosis. However, the large amount of heterogeneity among the study results prevents a definitive conclusion. The source of the heterogeneity is not clear. It is not obviously caused by differences in the definition of chronic cerebrospinal venous insufficiency, patient characteristics or the methodologic quality of the studies.”
They continued writing:
“We also could not identify any factor that accounted for the large and problematic difference between the studies in the frequency of chronic cerebrospinal venous insufficiency among patients with multiple sclerosis.”
According to the researchers, the difference could be due to the fact that the analysis included small sample sizes of the studies and also because of differences in ultrasound techniques and quality control, as ultrasonography results can vary depending on the training absolved and level of competence of each operator.
The authors highlight the fact that even if chronic venous insufficiency and multiple sclerosis are indeed linked, that this “…. does not mean that the condition causes multiple sclerosis.” Should prospective studies reveal that CCSVI really does occur more frequently in those suffering from multiple sclerosis, it could either mean that multiple sclerosis causes CCSVI or that CCSVI happens to occur more frequently in people with multiple sclerosis without actually causing the disease.
In a concluding statement the authors write that:
“Further high-quality studies, using identical ultrasound protocols, are needed to definitively determine whether chronic cerebrospinal venous insufficiency is more frequent among patients with multiple sclerosis than among those without it.”
Dr. Robert Fox from the Mellen Center for Multiple Sclerosis Treatment and Research at the Cleveland Clinic in Cleveland, Ohio, writes in a related comment:
“The meta-analysis by Laupacis and colleagues is a good starting point; however, much work remains to be done before we can be certain whether chronic cerebrospinal venous insufficiency is a paradigm shift in the classic sense … or just another fad.”
Written by Petra Rattue