As someone else suggested, you should ask for a referral to a board certified neurologist and let him/her do the MRI or other necessary for a diagnosis.
Anyone can guess at what it could be, but keep in mind that it takes an educated vet to examine your pup and do the appropriate testing to come up with a definitive diagnosis. My suggestion is to get a diagnosis FIRST before proceeding with other groups that are specific for one diagnosis. It may not be one of the things suggested...and if it is one of them, then you have the information.
If your vet does not know one, you can do a look up at:
http://www.acvim.org
I will keep your pup in my thoughts and prayers.