About 11 years ago I tried HBOT at enormous cost twice weekly for 60 minutes a time and continued for 2 years. I found it very hard to objectively measure if anything changed in how I felt.
My thinking was that if an anerobic bacteria was playing a role in my MS then flooding my body with Oxygen was a good idea as that would impact that sort of infection. The second reason was HBOT does promote wound healing. It is a recognised last line treatment for Gangrene prior to amputation as it can be effective and elite sports people use to speed healing from tears and heavy bruising. An MRI I had done towards the end of the period showed some resolution of white matter in my brain had occurred but as I was doing several things I can't say the HBOT on it's own did anything. I suspect it helped a little but I can't be definitive about it.
Ultimately, I decided the benefits I was experiencing came from the combination of Avonex and Valtrex and followed that path. After all this time time I still wonder about the HBOT but haven't gone back to it. I don't think it did any harm and I think I got some vague benefit but I can't say "yes, it helped my MS".
At the facility I went to I saw many infants with Cerebal Palsy being treated. They were generally too young to fake either symptoms or reactions. Clearly they benefited and their parents were generally over the moon. Again, they weren't cured but they could do some things after a time that they couldn't do at the start such a turn their bodies or lift their heads so I'm convinced it has a place for some things.
The authority is a man called Perlmutter. This is a link to his facility - http://www.perlhealth.com/perlmutter-hyperberic-center/