L.L.
IVIG therapy was only shown to be somewhat effective in ONE INDEPENDENT study, and as of 2010, had yet to be replicated...meaning, it basically doesn't work. There are also serious risks to consider with IVIG therapy and it sounds like it should be reserved for children with absolutely severe cases of pandas. It ALSO sounds like pandas is grossly overdiagnosed by pediatricians and family doctors, and that a diagnosis really needs to come from a specialist with experience in that area.
Who told you he needed this treatment? If you came up with it on your own (because if a dr. suggested it, he'd tell you where to go) I think I'd quit doing my own research and bring him in to see a specialist who KNOWS what to do for this. Sounds like physical and/or occupational therapy...what you'd normally do for tic disorders...is what's more appropriate. I would stop looking at the most radical treatment out there and look at the simple, noninvasive ones first. I mean, IVIG therapy is a big deal!