Without a professional diagnosis, it would be nearly impossible to diagnose a stroke in an aquarium fish. I have had fish panic, crash into the top or side of the aquarium, and then swim erratically. Some recover within a few days, others do not and after 4 to 6 weeks of not eating and resting on the bottom most of the time, they die.
I had four Leporinus Fasciatus in a 120-gallon community aquarium when one hit the tank wall, hard. Interestingly the other three Leporinus tried to lift it off the bottom and keep it swimming. This went on for several days, with the “helper” fish having some success, however eventually the erratically swimming fish died.