Our old girl had it once, as did my brother's old Weimaraner. It is scary to see. I have also personally had the human version (twice), an inner ear "vestibulitis" and it is awful. I think we used meclazine for dogs and me. I suggest using a crate with two doors - easier to get the dog out if you need to help her. All cases here passed in a few days.
Had to take my old girl into the vet last night because I thought she was having a stroke or the good Lord only knows what, vet diagnosed her with this "Old Dog" Vestibular Disease, gave meds for motion sickness and said it should pass in a few days, any advice out there how I can help to make her feel better? OMG it is heartbreaking to see my sweetheart suffering with this, she keeps falling cause no balance :{
One of my girls had it from age 11 to 15. It did get better and does resemble a stroke sometimes initially. Be glad your vet knew what it was, some don't. With some rest and time it should get better. For now, it is a pitiful sight. I am sorry for what you're seeing. I've been there but she did get better.
This happens to people even more often age 50 and upward. They call it vertigo but it's the same thing. My brother has it on and off in his 50's quite suddenly. The same for a friend in her late 50's, it came out of nowhere.
