I would keep up with follow-ups to make sure your veins remain open. I agree too that having even a few initial improvements bodes well for future gradual improvements, as long as the veins stay open. Do you know if you have any hypoplasia of the ascending lumbars? This might be more common in PPMS but can't be treated. Are you satisfied that your treatment was thorough? Sometimes issues are found with IVUS that wouldn't be found otherwise.
For stem cells, there was a recent discussion with Wheelchair Kamikaze, Bestadmom and Dr. Sclafani, related to a doctor's presentation at the July AAC symposium, who was combining CCSVI treatment with stem cells delivered into the carotid artery. This is a different area for stem cells to be delivered. If they're delivered venously, they might be filtered out by the lungs. Intrathecally meant injecting them directly into the spinal cord which might also not be as good as injecting them via catheter in the carotid, since from there they go directly to the target organ (brain).
Bestadmom also had some thoughts on how long it should be between harvesting stem cells and injecting them, so that there is time to sort (?) and grow the right kind (?).
This is getting past my area of knowledge but I think there is much potential in stem cells.