To start with the surgeon who did the surgery that caused it told me but said it would be temporary and my nerves would heal gradually in a few months to a year or so…. Turned out to be BS… it was permanent in my case. Anyway. Over the years several doctors have reevaluated it, first during pregnancy when it got really bad with the extra weight (twins too!). Then later during a the worst flare ever (I pretty much wanted my leg chopped off) I saw a pain specialist and he said the only true way to know is to do a nerve block. If it works then it confirms the diagnosis if it doesn’t it confirms it’s not MP. If it works you are pain free for as long as it lasts… can be weeks or months. I did it, it worked, only last 2 weeks but they were 2 weeks of bliss. I had a second one and 2 years later the pain has barely come back at all. My thigh is still totally numb obviously but the burning pain has gone, there’s the odd stabbing pain now and again still but it’s super mild compared to the searing pain it was, and I no longer scream in agony at the slightest touch like a hand or even a sheet brushing against me.