Hi there!
I was just wondering what it was that lead you to believe that a TENS unit could cause damage or exacerbate the RSD? I hadn't heard of any research that implicated it in the spread of RSD, and it really can be pretty effective. (I know this personally too!) A TENS really is just an external spinal cord stimulator- it works exactly the same way. If you wanted to discuss this, just send me a message- I'm actually a neuroscientist too. So I can help translate some of the literature, cause sometimes it's dense. And I was diagnosed with RSD when I was 11. Best of both worlds!
Linnie