Go to your DMV on the internet, and print out the form.
Have your doctor sign it, then fill out the rest, (signature) and send it back, to DMV.
With RSD, you'll fall under neurological disorders, probably.

I have a permanent plate for my vehicle, a mirror hanger for my other vehicles, (or any I might ride in) and a wallet card, for when you're standing in any line, gets you to the front, and other little perks.

I'm in PA and it's quite easy.

Pete
asb