Most insurances will cover pre-exsisting conditions after a period of 6 months of being on the insurance. You might have to check your plan to be sure. In other words if you have a pre-exsisting condition, your insurance will not cover you until you've been on the policy for 6 months. There is usually a clause that refers to pre-exsisting conditions that gives the exact time period.
As far as your time line, I would tell them of your problems several years ago and let the neuros draw their own conclusion. Hey it's not your fault you had a quak neuro. I would just want to tell them everything so they can make a DX.
In the meantime, check your time periods of your plan!
Good Luck
I went to a quack neuro who said my heaviness in my legs and the Raynauds I had was all from anxiety. I know now its livedo reticularis and not Raynauds. He flat out dismissed me and would not do anymore tests.
If your problems started 4 yrs ago, have you not seen a doctor before now? You are correct that you will be denied disability if you were not covered when the problems started.