you have to purchase the journal to read the letter, but it's worth it.
link to journal
Dr. Zamboni states that the Doepp study actually proves CCSVI exists--
when comparing levels of jugular blood flow between normals and pwMS during positional changes from supine to upright--
One of the major regulators of cerebral venous outflow is posture, due to the gravitational gradient between the cerebral parenchymal veins and the base of the neck (␣30mmHg).2 The authors demonstrate a much larger change in blood flow volume in normal subjects compared to MS patients when the subjects go from a supine to an upright position. They find a change of 128ml/min and 56ml/min for the right and left sides, respectively, for MS patients. But they find a much larger change of 266ml/min and 105ml/min for their normal subjects. This result actually suggests the presence of chronic cerebrospinal venous insufficiency (CCSVI). Possible causes include intra-luminal septum, membrane, and immobile valve affecting the hydrostatic pressure gradient in the upright position. The presence of such blockages in the extracranial and extravertebral cerebral veins has been proven also by using catheter venography, the unquestionable gold standard in medicine.3,4
There's much, much more. It is a very illuminating letter-