That is correct. Look for signs of recovery in 72 hrs. Supportive care ( fluids, anti-nausea drugs) and time. Usually a diagnosis is made by exclusion, ie recovery over time. I assume the veterinarian has done a complete exam and Blood work. If inner ear infection is suspected, he should be on antibiotics. U of Guelph for advanced diagnostics if your veterinarian feels it is appropriate. Leanne has seen a few, they are challenging because the symptoms can be caused by other diseases, but it seems your veterinarian has gone through those rule-outs and given you a course of action.
We are both AVC (UPEI) grads.
Regards
Paul