CCSVI: Part 2
In my previous post, I wrote about the Italian vascular surgeon, Paolo Zamboni, who coined the term, “Chronic Cerebrospinal Venous Insufficiency (CCSVI).”
From the beginning, many MS neurologists were skeptical of Dr. Zamboni’s proposal. His ideas flew in the face of decades of thinking about the illness being primarily the result of the immune system gone awry. Additionally, there were several features of the illness that seemingly could not be explained by CCSVI:
- MS begins as a relapsing-remitting disease in over 90 percent of patients. This means that patients suffer from acute attacks that come on over hours to days and then spontaneously heal in the majority of patients. How, then, can blocked venous drainage, presumably a condition that does not fluctuate, produce this pattern of illness?
- There are other illnesses (such as congestive heart failure or conditions where blood clots form in the cerebral veins) where venous drainage is impaired. Yet these patients do not develop any illness resembling MS.
- MS is well-known to have a geographic gradient where it is more common further away from the equator. How could CCSVI explain this?
- Finally, even if it is the case that veins are abnormal in patients with MS, perhaps these abnormal veins do not necessarily cause MS, but rather are also a consequence of the same disordered immune system that is thought to be the primarily problem in MS. For example, patients with diabetes have abnormal blood vessels as well, but these are recognized to be a result of the diabetes, and no one would suggest placing stents in the arteries of diabetics to cure their diabetes.
- Finally, it is not clear to what extent the evaluation of the venous system via ultrasound depends on the technique and experience of the ultrasound technician.
In a recent issue of the journal Neurology, the largest CCSVI study to date was published. This study investigated three categories of subjects:
- those with MS
- those with other neurological diseases
- healthy controls
There were a total of 499 subjects in the study, and all studies were performed by a single ultrasound technician, who was aware of the MS status of each patient. The study found that 56 percent of patients with MS met criteria for CCSVI, as did 23 percent of healthy controls and 46 percent of subjects with other neurologic diseases. These results demonstrate a high prevalence of CCSVI in patients with MS, but far less than the 100 percent initially reported by Zamboni.
Additionally, a high number of healthy controls and patients with other neurological diseases were found to have the same ultrasound changes. The primary investigators concluded that “our findings point against CCSVI having a primary causative role in the development of MS.”
Another study published in August 2011 in the journal Neurology investigated 60 patients with progressive MS. Only four of them were found to meet criteria for CCSVI, and the authors of the paper concluded that “our findings indicate that CCSVI is not a late secondary phenomenon of MS and is not associated with disability.”
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