A lady with MS where I live, was having very similar issues: Terrible fog and she felt as if her back of the neck was boiling. We discussed about her issue and I told her about CCSVI and that she has nothing to lose by having herself scanned.
She has found multiple stenoses, so obvious, that they were directly visible by the ultrasound itself, without even using the echo doppler to have the blood speed measured.
When you are uprigt, the IJVs collapse. If they are already narrow, they will block completely, making it even worse.
Shortest joke: "We may not be able to cure MS but we can manage its symptoms."