Lori - this may be out of left field, and I haven't read this whole thread, but I am pretty sure that certain kinds of scoliosis are a symptom of a tethered spinal cord (which is diagnosed by MRI). I recall that from my reading last fall. My ds5 (who has SPD, among other issues) was discovered to have a tethered cord and had surgery to release it last October (by a pediatric neurosurgeon). He did not have scoliosis as a symptom, but I'm constantly looking for scoliosis in the other kids because they too have wierd butt crack issues (sacral dimples, etc.). In ds5's case, his tethered cord was caused by a filum lipoma (fatty filum) and the surgery was fairly simple. I'm just glad it's fixed because that can prevent further neurological deterioration as he grows. To the extent that a tethered cord causes neurological issues, they can be permanent (sometimes/often) though some patients see improvement following surgery.
My point is that if, by any strange chance, your child's scoliosis was caused by a tethered cord, it may be surgically fixable - releasing the tether may greatly improve the scoliosis. Just thought I'd throw that out there in case the ped hadn't considered that possible cause. It may be well worth at least asking the question.
sending hugs from the land of strange, random medical issues
p.s. it's a long story, but I was the one who identified the possible issue with ds5 and brought it up to the ped. (I was googling about the baby's sacral dimple and came across some info, and then remembered ds5's symptoms.) His symptoms were potty issues (constipation and voiding problems) and a tiny skin tag in his butt crack that the ped didn't know about. When I mentioned it, she wanted to see him right away, and then immediately ordered the MRI. We were both surprised with the result. Now his ITP seems to be turning into congenital thrombocytopenia - the land of strange medical issues...