Hi CG,
As far as blocks being invasive it would be considered so because of the nature of it.
But as far as causing spreading it varies from case to case.
I had three done to my ganglion nerves in my neck/shoulder area with no triggers or results. I've had full body spread since but not related to the blocks.
Sort of a hit and miss kind of a thing. Some find good results and it's something neurologists want to try in most cases to use as a control test if nothing else. A lot can be learned by them. Even a negative result says something.
Blocks can be performed in most any area if done correctly by an expert.
I hope that if you choose this that it helps you find relief and leads to a pain free life.
I believe that all avenues available to us should be explored fighting this monster.
Best of luck to you in your fight...