Not sure what your story is, but if your SC condition has worsened since your initial rating, don't wait for an invitation. Go see the DAV and have a service officer help you apply for an upgrade. They do re-look at everything, so you do want to be sure things got worse, not better.
If your original rating was considered permanent with no chance of it improving, then they would not bring you back for a re-evaluation. As an extreme exapmle, A person who lost an arm and received a rating for it would not be called back. His condition is not going to change, his arm will not grow back.
I would not contact the VA unless your service rated condition has gotten worse. There is always a chance they could decide that your condition has improved and lower your rating.
But as BMCS stated if your condition has gotten worse you should contact the VA.
No - it has not worsened nor improved. I'm luckier than most but was curious if I was overlooked. i'm staying away from them unless / until it worsens. thanks for the input guys. Bill