The main difficulty is getting across the concept of “intermittent and fluctuating”.
We can define “disability”. We've done a good job in defining disability in surveys, but it's to get across the idea that an episodic disability isn't like being in a wheelchair. It comes and goes. It's the fluctuating and the intermittent nature. It's never knowing when you're going to have a migraine and never knowing if the migraine is going to be totally debilitating or just a headache. It's that unknown....
Associated with episodic disabilities is the fact that it brings in other things like fatigue, primarily, which goes along with it, and then all the attitudinal barriers this individual faces as a result of it.