There is a continuing controversy over the hypothesis, first proposed by Italian vascular surgeon, Dr. Paolo Zamboni that multiple sclerosis (MS) is caused by chronic blockage of the veins that drain the brain, called Chronic Cerebrospinal Venous Insufficiency (CCSVI). The current scientific consensus is that MS is a chronic autoimmune disease, and the pathology is caused by primary inflammation. Dr. Zamboni believes that the venous anomalies he has discovered are the primary cause and the inflammation is secondary.
If true, Zamboni's hypothesis of CCSVI would be a major paradigm change for MS. It also holds out the promise of a new effective treatment for MS, endovascular treatment - using expanding balloons to open up the narrowed or closed veins.
These kinds of controversies take place all the time in medicine. Many diseases are complicated and imperfectly understood, and there are competing theories to explain what we observe. Often there are competing treatments with interesting strengths and weaknesses. While definitive evidence is lacking, personal opinion holds sway. In the best case scenario rigorous studies are performed and a generally accepted standard of care is built on the evidence.
Sometimes, however, controversies seem to take on a life of their own, and move into the ideological and political realm where evidence may not hold final sway. It seems that this has happened with the CCSVI controversy.
First, let's take a look at the current state of the evidence. In Zamboni's original study he claimed that 100% of MS patients had significant blockage in the large veins that drain the brain. Before we move to theories and studies about how this relates to MS and whether or not treatment is effective it makes sense to test this original observation. If it's true, then more research is warranted. If not, then we move on.
There have been a number of attempts to replicate Zamboni's findings, or use other techniques to investigate venous draining to see if it correlates with MS. The results of these studies are (as is almost always the case) mixed. No study has found the 100% results that Zamboni did. Some studies find a correlation between blockage and MS, sometimes there is also an association with other neurological disorders, and in some studies there is no association at all.
In a 2011 review Awad et. al. concluded:
"Currently, there is inconclusive evidence to support CCSVI as an etiological factor in patients with multiple sclerosis. Endovascular procedures should not be undertaken outside of controlled clinical trials."
Of note studies have failed to find an association between MS severity and CCSVI, arguing against a causal relationship. Further, studies looking at venous blockage show that only those with >80% blockage had any significant effect on venous function, so lesser degrees of blockage are probably not clinically significant.
Having looked at many such controversial issues, my impression of the literature to date is that it is most consistent with the null hypothesis - that CCSVI is not a real and clinically significant phenomenon. The spread of results and lack of clear causal association is consistent with (or at least compatible with) the kind of research noise we see when there is no clear signal.
This is different than concluding that the evidence is sufficient to confidently rule out an effect. We are not yet there with CCSVI, and therefore there is room for further research with rigorous blinded designs to settle the issue definitively.
Because this is a medical question the issue is complicated by treatment decisions - should we treat MS patients for alleged CCSVI while the data is still inconclusive? This is as much an ethical question as a scientific question. The concept of compassionate use of experimental treatments for otherwise incurable illnesses is generally accepted, but is very tricky in the details of application.
MS can be a very severe and debilitating disease, and response to existing treatments is variable. There are certainly patients who have progressive disease despite our best current treatment. Desperate patients are often willing to try any new treatment that promises benefit.
At the same time it is not ethical to offer highly implausible treatments to patients that are not supported by at least some evidence. Here, when it comes to CCSVI, experts disagree. Some think there is insufficient reason to progress to clinical trials or to offer compassionate treatment, while others believe that both are indicated.
Here is where politics intrudes, especially in Canada where this has been a hot issue. Patients are seeking treatment for CCSVI (the so-called liberation procedure) and clamoring for clinical trials. Some vascular doctors and supporters of CCSVI are also. Most neurologists, however, remain skeptical and think it's premature to progress to clinical trials.
These are the kind of issues that should be resolved at scientific meetings and in the literature, with experts fighting it out. Instead, politicians with little medical background are taking charge of the issue with political posturing.
The response of some patients in the MS community has also been unfortunately, and perhaps a reflection of the times. Comments to articles on this topic are full of conspiracy mongering, claims that neurologists are just protecting their turf, and accusations of Big Pharma influence and corruption. There is a disturbing disconnect between the science and evidence-based discussion that is happening among experts and the fairy tale view of villains and heroes reflected in the public and political discourse.
The intense anger and distrust on display is very counterproductive, and makes me wonder what is its source. Has it always been this way, or is this something new (at least in its magnitude)? I suspect that the rise of the alternative medicine movement and the internet are playing a role. Promotion of anti-mainstream medicine sentiment and distrust of institutions, the government, the "medical industrial" complex, and Big Pharma are all part of the promotion of unscientific medical modalities. I suspect that a lot of the venom we are seeing in the CCSVI debate is being fueled by the spread of these sentiments generally on the internet.
Meanwhile, the science trudges on. It seems likely at this point that what will happen is further studies will either be mixed or negative. CCSVI will not gain mainstream acceptance because the evidence will not support it, but it will continue on the fringe - to what extent remains to be seen. Of course, it's possible that there is some truth to the claims of CCSVI, in which case that is eventually what the scientific evidence will show, but I think that is unlikely given current evidence.
Steven Novella, M.D. is the JREF's Senior Fellow and Director of the JREF’s new Science-Based Medicine project.
Dr. Novella is an academic clinical neurologist at Yale University School of Medicine. He is the president and co-founder of the New England Skeptical Society and the host and producer of the popular weekly science show, The Skeptics’ Guide to the Universe. He also authors the NeuroLogica Blog.