Chronic cerebrospinal venous insufficiency (CCSVI or CCVI) is a term invented by Italian researcher Paolo Zamboni in 2008 to describe compromised flow of blood in the veins draining the central nervous system.

[16][17] Proposed consequences of CCSVI syndrome include intracranial hypoxia, delayed perfusion, reduced drainage of catabolites, increased transpulmonary pressure,[18] and iron deposits around the cerebral veins.

[21] Zamboni and colleagues claimed that in MS patients diagnosed with CCSVI, the azygos and IJV veins are stenotic (abnormally narrowed) in around 90% of cases.

Zamboni theorized that malformed blood vessels cause increased deposition of iron in the brain, which in turn triggers autoimmunity and degeneration of the nerve's myelin sheath.

[19][22] While the initial article on CCSVI claimed that abnormal venous function parameters were not seen in healthy people, others have noted that this is not the case.

[1][22] Such outstanding results have raised suspicions of a possible spectrum bias, which originates on a diagnostic test not being used under clinically significant conditions.

[25] The poor reproducibility across studies and diagnostic modalities has led some authors to conclude that CCVSI might be nothing more than a clinically irrelevant sonographic construct.

[26] It was agreed that it was urgent to perform appropriate epidemiological studies to define the possible relationship between CCSVI and MS, although existing data did not support CCSVI as the cause of MS.[13] Most of the venous problems in MS patients have been reported to be truncular venous malformations, including azygous stenosis, defective jugular valves and jugular vein aneurysms.

[36] Others have stated that magnetic resonance venography is a valid measure which has advantages over Doppler including the fact that results are more operator-independent.

[3][5][7][22][38][39] Moreover, the CIRSE has stated that treatment research should begin by a small, placebo-controlled, prospective randomised trial which should be monitored by an independent organization.

[40] In March 2013 a press release indicated that the first prospective, placebo-controlled study of balloon angioplasty for MS had not shown any benefit of the therapy.

[41] Kuwait became the first country in the world where treatment of CCSVI, as of 2010, was explicitly allowed by the medical authorities and paid by the state health system.

[14] Balloon angioplasty in a preliminary, uncontrolled, unblinded study by Zamboni improved symptoms in MS in a minority of treated people.

[15] While the procedure has been reported to be generally safe for MS patients,[13][41][46] severe complications related to the angioplasty and stenting that have been reported include intracranial hemorrhage, stent migration into a renal vein, thrombosis and nerve compression syndrome of cranial nerves XI and XII.

[37] Some United States hospitals have banned the surgical procedure outside clinical trials due to safety concerns until more evidence to support its use is available.

[48] Later, in 1935, Tracy Putnam was able to produce similar lesions in dogs blocking their veins[49] The term "chronic cerebrospinal venous insufficiency" was coined in 2008 by Paolo Zamboni, who described it in patients with multiple sclerosis.

[8] These are potential conflicts of interest that he has never disclosed when publishing scientific articles, which would be against ethical practices of some countries such as the United States.

[14] Moreover, the CCSVI case has been considered a good example of how new communication technologies and social media are modifying the traditional relationship between science, politics, medicine, and the general public.

People with MS often read extensively about the CCSVI theory and its development on Internet sites,[52] and a search for "liberation procedure" in Google as of August 2010 yielded more than 2.5 million hits.

[50] Social media have served patient groups in their attempt to pressure official bodies to make decisions favoring funding of clinical trials, or the public coverage of stenting and venoplasty as treatments of MS.[50] Likewise, social media have been accused of creating a division between CCSVI supporters and those who say it does not work.

[50][51] Indeed, they have been repeatedly used by advocates of the CCSVI theory to attack those who were more critical or cautious, most commonly with accusations of being tainted due to commercial relationships with pharmaceutical companies.

[50] The debate regarding funding in Canada has been considered to be specially informative as an example of extreme involvement of politics, due to public pressure, in decisions usually governed by scientific evidence.

[56] The MS Society of Canada in September 2010 reserved one million dollars toward CCSVI research "when a therapeutic trial is warranted and approved.

[60] British Columbia, Alberta, and Newfoundland and Labrador funded observational studies in which patients who had already received the treatment were included.

[64] Conversely, the other study concluded that sense of community and cooperation (from family, MS groups and the general population) was a key motivating factor.

[65] Other motivating factors included media reports, perception of approval from their health providers, the apparent low risk of the operation, or accessibility of the hospital that offered the procedure directly or through a medical tourism company.