My 16-year-old dog is suddenly suffering from disorientation and often walks in circles. Is it a stroke?

She also suffers from liver dysfunction, and was put under total anesthesia 3 weeks ago in order to remove some superficial tumors from her ears. A couple of days ago she vomited and had diarrhea, and since then she walks around the house senseless and disorientated- she often stops at corners without knowning where to go, or walks in circles- and cannot rest. She recognises us but we cannot confort her. She has lost her appetite and does not drink water. The vet could not give a diagnosis and mentioned the possibility of a stroke. Does anyone out there has any idea of what this may mean? Despite her age she has been a very lively dog (people would not believe that she is past 16yrs old...)