All I can say is that the TN association has 8 classifications of TN. Pre TN is not in there (yet?). I think it's just an MD's way of putting a name on something they just don't know. As if that makes it better?

There are any number of conditions that cause facial pain but in the end they are all mostly treated as if it were TN. I think many of us experienced TN for many years and did not look into it or know what it was because it was milder than the TN we face now.
So if they are calling the earlier stages of TN preTN then that's what they are doing. In the end, start treating it like it was TN and perhaps you can prevent it from getting much worse or at least slow down the progression.

Stop using aspartame, MSG, caffeine and all tooth whitening products. Get good sleep even if that means taking an RX or OTC med. Avoid stress as much as possible, eat properly (always my failure) and learn to meditate or relaxing therapies...

Hang in there,,keep coming back we are here to help...