Background
Chronic cerebrospinal venous insufficiency (CCSVI) describes a theory first posited in 2008 by Dr. Paolo Zamboni (University of Ferrara, Italy) hypothesizing that people living with multiple sclerosis experience narrowing or blockage of the veins in the head and neck, resulting in the build-up of blood. According to this theory, in order to compensate for the increased pressure of accumulated blood, new blood vessels develop to accommodate the reflux of blood back into the central nervous system. Since these new vessels are structurally weaker than the core veins, they may be prone to leaking blood into the surrounding tissue and depositing iron into the central nervous system, in turn triggering the autoimmune immune attack underlying MS.
A new study published by Dr. Carlos Torres (University of Ottawa) and a team of collaborators employed powerful imaging technology to examine vein anatomy in people living without MS. The purpose of the study was to answer the question: are differences in vein anatomy associated specifically with MS or are they simply a source of natural variation in the general population? The study was funded by an operating grant from the MS Society of Canada and was published in the journal European Radiology.
The Study and Results
The researchers recruited 100 individuals living without MS to the study and used advanced imaging technology, including contrast –enhanced magnetic resonance imaging (MRI) and magnetic resonance venography, to reconstruct detailed images of the system of blood vessels that drains blood from the brain and spinal cord on both sides of the body, particularly the internal jugular veins and vertebral veins. Two trained neuroradiologists independently reviewed the images to document any notable characteristics and variations in the anatomy of the blood vessels.
Evaluation by both neuroradiologists consistently found that approximately 75% of the healthy participants exhibited asymmetry (including narrowing) in the anatomy of their internal jugular veins, and half showed asymmetry in their vertebral veins. Many of the participants also showed enlargement of the extracranial veins (such as the external jugular veins), an observation that has been postulated to be linked to CCSVI in people with MS as a compensatory mechanism for narrowing of the internal jugular veins. Together, these findings led the researchers to conclude that normal variation in anatomy of the veins draining the brain and spinal cord refutes the hypothesis that CCSVI is exclusively associated with MS.
Comment
This study is one of seven research projects that received $2.4 million in joint funding from the MS Society of Canada and National MS Society (USA) in 2010 to investigate the relationship between CCSVI and MS. The results of this study by Dr. Torres add to the mounting evidence demonstrating that a link between CCSVI and MS is unlikely; for instance, a study led by Dr. Robert Fox (Cleveland Clinic, Ohio) published last year similarly concluded that CCSVI is not exclusive to people living with MS, and appears to occur at the same rate in healthy people living without MS. The MS Society of Canada continues to support the Canadian CCSVI trial, and is committed to funding research that will provide answers about CCSVI to people living with MS.
Source
Torres C et al. (2016) Extracranial Venous abnormalities: A true pathological finding in patients with multiple sclerosis or an anatomical variant? Eur Radiol. [Epub ahead of print]