What is Neurofibromatosis?

This is what it's like.
Saturday. 3pm. Jazz class. Emerson says dance class gives him "super jazz power." He makes Jazz Hands when he says this. He's such an adorable little goof, but I worry that the other kids in his class are bigger and seem so much more mature. Of course he is the only boy.

He lays down on the floor in the middle of stretching. Fifteen minutes into the class he's not listening to his instructor, pretending to fall asleep. Finally he leaves.

I don't know whether he's goofing, accidentally hit his head, or if this is something from the NF. Could a brain tumour cause this? Is that why I've been noticing that bulging lump above his eye?

He's tired. And it makes no sense because he got plenty of sleep. And whereas most parents would think "maybe he's coming down with something," as the parent of a child with NF you think "maybe he has a brain tumour."