I'd associate it with getting better. For about a month, probably longer, after I started to try walking at home, the pain was excruciating. As in: it would take me 30 minutes to creep (on legs) from the head to the foot of my bed. I'm a strong person physically and mentally, but I'd have to stop to rest and motivate myself.
A few years down the road, I barely remember that. There's definitely back pain. Occasional pins-and-needle pain that comes and goes, especially with stress, extreme weather changes/temps. Other random pains.
I cannot respond to the IVIG part. No idea at all.
And as with almost all things medical, no two patients are exactly alike in their experiences.
Nerve pain is some of the worst pain to have, whether it is from compression, tears or regeneration of them. It is difficult to say for sure what is going on here, since all aspects of it can be extremely painful Improvement of symptoms is one way to determine it's efficacy. People do see improvement but have good days and bad days, as with most diseases. To my knowledge, it's not curable, however.