Just merely curious, I know this used to be kind of a big thing in Spaniels maybe in the 90's-early 00's, but it seems to have kind of dissipated through the years. Used to see people come on forums and blame aggression on 'Rage syndrome', I think it was in the news too, but I really haven't heard anyone mention it in some time. Even a google search shows most forum topics about it are 2007 and prior.
Is it still a 'thing'? Was it ever really a 'thing'? Have you ever known a dog that might have been affected?