I experienced a sort of similar procedure decades ago, before MRI’s, that required precision and risks. Had to get myelogram injections in the ‘80’s, a spinal tap to inject dye into the spinal fluid. I had 3 done, one at a time, minimal pain med/anesthetic is given.
Basically you bite the bullet as the needle is inserted in and hope no nerve gets knicked, which mine weren’t, but they do get touched, mine did. It shoots pain bolts down your legs and causes hard back spasms but you cannot move from them, if you do the dye can leak and cause unbearable headaches, though some sort of headache is typical as most do move a little, and laying flat for 24hrs. afterwards is common to relieve it.
I got through it well and only had to lay flat for about 4hrs afterwards as I developed no headache at all.