Hello,
I know this is an old string, but I'm convinced my 2.5 year old has EIC but is clear genetically. After 10 minutes of ball fetch in 65 F sunny not humid weather, (granted this is warm for what we are used to in Anchorage) he has lost coordination in back legs, stumbled, fell over, etc. I have seen it twice and avoid by watching closely for symptoms, but twice friends have reported it happening on their watch. He recovers quickly (not heat stroke) and is aware and listens to commands during the episode (not epilepsy). He doesn't seem worried, just tired, panting, and happy because he is doing his favorite thing, fetch. Anyway, wanted to throw my two cents in.