Kitty he can only hear the whoosh of the arteries with a stethoscope, I think. Not the jugulars next to them. They only flow down, not pumped by the heart.

They only flow when you lay down. While in an upright position they don't flow, the vein collapses. With CCSVI or any blockage, nothing may flow.

Did he check you while you were laying supine? Perhaps he could hear something with stethoscopes of today.

Your brain drains blood without oxygen down by itself to the heart to get more oxygen from the lungs and then the arteries pumps it back up to the brain so we don't get fatigued, etc. without enough oxygen.

No pump in the brain, so it can back up very easily, like a clogged drain. Not with plaque, that is only the arteries.

The veins get kinks, bones compressing them, webs, valves reversed or missing, twists and turns and more. It happens. They think it is congenital. Just something the happens in the womb. We are not all born perfect.

Something triggers it to occur in the womb. Like lack of sunshine to Mom's in the winter pregnancy, thus more born with MS in the summer months.

Sorry to ramble.