TN can be a funny disease and does not always show up on an MRI no matter what kind you have. it is best to get a thin slice with contrast. it has a better chance of showing a compression. Even if you have the right MRI and it shows nothing, it does not mean you do not have a compression. there are some Dr that will tell you you that if a compression doesn't show up, then it is not there.
I had a compression and it did not show up on my first MRI. I did have a second MRI that showed a compression and had MVD surgery. I had already decided to try MVD even if I did not ace anything show up. there are some very excellent neurosurgeons, including the Dr that developed the MVD surgery that feels your symptoms are the best indicator of what type of TN you have and whether an MVD will be successful.
I had a second MVD because my pain came back after a few weeks and they opened me back up based on my symptoms and fixed a problem. they did not even feel the need to do the MRI.
I guess I would ask the question, what are you trying to accomplish with the MRI. Are you thinking about having an MVD? Do you just want a possible confirmation that you have typical TN? if you are just going to try the meds right now and see if they help and aren't contemplating surgery, then it may not be worth the cost to you right now.
I always wanted to know everything I could and would have paid whatever I could to find out and fix this terrible disease.
I have read several of your posts recently, but not all. have been sick the past few days. I remember you have lupus - I have Sero negative RA, with crossover symptoms. my rheumatologist always tells me that even though I fit RA, she thinks I have some weird, rare auto immune something. She also thinks that there has to somehow be a connection to my TN and autoimmune problems.