My previous dog Flip had this. There are 3 known causes, though there may be others. A deep inner ear infection, swollen nerves leading to/from the inner ear or a tumor pressing against the inner ear. I did not have a good experience with this, but that's likely because of how far gone Flip was before I was told of his condition. I had left him with my parents when I moved for college and couldn't take him. By they time they told me something was wrong he hadn't eaten in a week. He was OK walking if he had a line to follow or was leaning on me. He tried to eat and would be very happy to see me coming with the food bowl, but couldn't eat more them 1-2 bites on his own. I ended up tube feeding him for a while, because he was hungry but the IVD was causing "sea sick" like symptoms. I only kept going because he was still going. He'd see me coming and his tail would wag and his eyes would light up. I stopped his pain the morning he started having seizures. His IVD was cause by a tumor pressing against his inner ear and brain. I couldn't let him keep going after that.
My experiences aside. I've know other elderly dogs with IVD who have done wonderfully with simple supportive care after an episode, and have gone on to live several more happy years without another episode, and those that have had occasional episodes here and there.