New results from MS Society of Canada funded study exploring CCSVI and MS
Background: Determining the link between CCSVI and MS
Chronic cerebrospinal venous insufficiency (CCSVI) is described as a condition in which the veins in the head and neck are narrowed or blocked (an effect known as stenosis) and therefore unable to efficiently remove blood from the brain and spinal cord. It is purported that obstruction in the veins can result in increased levels of iron in the brain, triggering autoimmune events leading to MS. CCSVI is a term developed by Dr. Paolo Zamboni, a vascular surgeon from Italy who, in 2009, published an article reporting the presence of CCSVI in a large group of MS patients. This evidence spawned much debate in the MS community, and since then CCSVI has remained an important topic of research around the world.
In June 2010, the National MS Society (USA) and the MS Society of Canada committed over $2.4 million to support seven new research projects that would gain further insight into the relationship between CCSVI and MS. These seven studies were designed to observe the structure and function of veins draining the brain and spinal cord in people with MS, and compare them to structure and function of veins in healthy volunteers as well as people with other neurological diseases.
Dr. Jerry Wolinsky and colleagues from the University of Texas Health Center in Houston were first to publish results from their study, which suggested no association between CCSVI and MS as seen on conventional ultrasound. They took the study one step further and observed venous drainage in the same group of patients using alternative imaging techniques to determine if the results are similar or different to those collected from ultrasound.
The single-centre study enrolled 206 MS and 70 non-MS volunteers. The first aim of the study was to compare the prevalence of CCSVI as defined by neurosonography (ultrasound of the brain) in people with MS versus non-MS controls.
Of the 206 participants with MS, 98 were then subjected to intravascular contrast-enhanced 3D magnetic resonance venography (MRV). This is a highly sophisticated procedure in which a dye is administered to the patient to enable the scans to provide detailed images of the veins and observe blood flow in the head and neck.
Of the 98 people with MS who underwent both ultrasound and MRV, 40 were examined using transluminal venography (TLV). This approach involves obtaining internal images by surgically inserting a catheter into the vein. In this study, the azygous and internal jugular veins were examined as narrowing or blockage of these veins is a believed to be a hallmark of CCSVI.
Data collected from MRV and TLV images were compared to what was observed for the same patients using ultrasound.
Magnetic resonance venography (MRV)
In 71 out of 98 people with MS, neither ultrasound nor MRV detected the presence of CCSVI. In 26 out of 98 people with MS, ultrasound images that may have shown stenosis did not show stenosis on MRV, and vice versa. The research team reported that MRV may have advantages for imaging certain regions of the venous system that are poorly detected by ultrasound, which may account for the discrepancy.
Transluminal venography (TLV)
Of the 39 azygous veins examined, one showed minimal vein narrowing. About half of the internal jugular veins studied showed highly variable degrees of stenosis; the stenosis varied between 10-90%. Despite this, TLV findings suggest that any stenosis present is not of clinical significance.
Overall, additional findings from the study lend no support for altered venous flow in people with MS, and suggest that CCSVI does not likely contribute to the MS disease.
New data from Dr. Wolinksy’s study sheds light on important questions regarding imaging techniques used to detect CCSVI. While most research on CCSVI and MS, including work by Dr. Zamboni, employs ultrasound to view the venous system in detail, there are other imaging methods that have the potential of identifying changes in vein structure with greater accuracy. Results from the other funded studies are expected in the coming months, and will provide further information on CCSVI and its implications for people with MS.
Brod SA et al. Chronic cerebrospinal venous insufficiency: makes multimodal imaging assessment. Multiple Sclerosis Journal 2013 4 July [Epub ahead of print]