Have you had a
MRI scan of the brain, and spinal cord?
What bloods have you been tested for?
Have you had any auto-immune blood tests done, ? ANA, DNA, ANCA. etc....
This could be one of many diseases, from neurological, to auto-immune, to vascular.
The way i would go about this , is to write down everything you have had done, ie what tests and then start ruling out what it could possibly be from what it is definately not.