Your pup could be experiencing a bout of 'old dog vestibular syndrome'.

This is a very scary 'for the owner' but not permanent for the dog occurrance. It seems to be related to a bacterial infection of the inner ear resulting in seisures that manifests itself in symptoms that would indicate a stroke or possible epileptic seisure. Check the dogs eyes. If they scan back and forth then it is in fact ODVS. If you confirm send me an e-mail to discuss treatment.