It’s unusual to feel the shocks all over?

Altho I don’t think It’s unheard of.
I’ve searched the web to try and learn about how, why and how it feels when nerves die and then regrow. Do searches yourself, but you’ll likely find deep deep research on sea slugs or newts.
The sense of all I’ve read is that when nerves die? There are big shocks as their circuits aren’t completed anymore. When they start to regrow? Similar shocks go out trying to find their connections! Sometimes it works? Othere not.
The pain at onset that you escaped? I GOT and big-time. Tho? At times not-feeling ANYTHING can be more distressing as feeling the pain..[at least you know somethings’ sort of working-tho not well?] Personally, I’d rather have the pain, unless it’s to the can’t complete a sentence point..know what I mean?
I’m guessing that your IVIG is the process of helping stop nerve deterioration and that nerves are trying to CONNECT! Gotta warn you? At times those new ‘charges’ will make you gasp!
I’d try to keep a sort of notepad of when these zaps occur and how long they are? As well as how often. Docs love these sort of facts, tho they do little with them? They could use such comments to justify more IVIG. Better for you in that it makes your insurance company happy.

Paul? The lower back pain could be either liver or kidney issues…were you super hydrated before, during and AFTER infusions? There’d be a lot of ‘wastes’ to tax these organs and hydration helps things along a lot easier.
I’ll be blunt, you cannot almost hydrate too much at such a key time. Just do it till you slosh slitely and afterwards for two days? Then it’ll be lots easier.

Good luck to both or you!