Several new studies are pointing against the theory that narrowed neck veins are the primary cause of multiple sclerosis.
The condition, called chronic cerebrospinal venous insufficiency, or CCSVI, became the subject of numerous studies after Italian vascular surgeon Paolo Zamboni hypothesized that it could be to blame for MS.
Dr. Zamboni has speculated that reduced blood flow leaves iron deposits in the brain, leading to the neural lesions typical of MS. He suggests that reversing the condition by unblocking neck veins using balloon angioplasty could help alleviate symptoms, and many hopeful Canadian MS patients have gone abroad to have the procedure, which isn't offered in this country.
A study involving Doppler ultrasounds of 499 subjects, led by neurologist Robert Zivadinov of the University of Buffalo, has added to doubts about the theory.
The study, published in the journal Neurology, found that the prevalence of CCSVI was 56 per cent in patients with MS, 42 per cent in patients with other neurological diseases, 38 per cent in those with clinically isolated syndrome, a precursor to MS, and 23 per cent in healthy controls.
"Our findings are consistent with an increased prevalence of CCSVI in MS, but with modest sensitivity/specificity," the researchers concluded. "Our findings point against CCSVI having a primary causative role in the development of MS."
The study included 289 people with MS, 163 healthy controls, 26 people with other neurological diseases and 21 with clinically isolated syndrome.
An accompanying editorial in the journal says the study suggests that CCSVI, as defined using ultrasound of the intracranial and extracranial venous system, is not likely to be a primary causal process in MS.
"An increased prevalence in progressive as compared with relapsing disease leaves open the possibility that CCSVI may be playing a contributory role in, or be a consequence of, the disease, or may be age-related," authors Robert J. Fox and Alex Rae Grant wrote.
Given the uncertainties of the relationship between CCSVI and MS and the potential risks of intervention, they said balloon venoplasty should be restricted to "a blinded, controlled clinical trial using carefully chosen clinical endpoints and appropriate patient-safety oversight."
"It behooves the clinical research community to carefully pursue CCSVI to its end," they wrote. "We should neither jump on the bandwagon as it passes through town, nor assiduously miss the parade."
A number of other, smaller studies on the subject were presented this week at the annual meeting of the American Academy of Neurology in Honolulu.
A study led by Katayoun Alikhani of Calgary included 67 people at the city's University Hospital who underwent magnetic resonance venography of their neck veins.
Among the findings: vein abnormalities were found in 20 per cent of those with MS and 20 per cent of those without MS.
"This first independent Canadian MRV study confirms neck vein abnormalities are infrequent and independent of the diagnosis of MS," the researchers wrote in their conclusion, noting that larger, controlled, blinded and more comprehensive studies are under way.
Another group in Europe assessed whether venous drainage from the brain was impaired in 94 patients with MS and 20 healthy control subjects. Their findings provided compelling evidence against a significant role of cerebro-cervical venous congestion in causing MS, they concluded.
"Against this backdrop, interventional treatment attempts to cure a non-confirmed condition (CCSVI) seem unjustified," they wrote.
The Canadian Press