Derpy explains her medical condition to her daughter.

Scootaloo opened her eyes, she hadn't remembered closing them. She just remembered practicing flying with Rainbow Dash. Scootaloo looked around, there was her hero. She was looking at something, tears in her eyes and a distraught look on her face. Scootaloo couldn't see what Rainbow was looking at, the image was fuzzy.
"Rainbow Dash." Scootaloo said uneasily. She didn't like seeing her idol like this, it looked wrong.
"She can't hear you right now Scootaloo."