Hi! My Daughter, 13, Has Been Having Uncontrollable Head Drops.

Hi! My daughter, 13, has been having uncontrollable head drops. What i mean by this is that in the middle of the day, randomly, her head will just fall, only for a split second, then shes dizzy for a couple minutes, and then everything is back to normal. She says it feels like theres an earthquake going on and her head just jerks downward, without control of her neck or head. She also says she blacks out for a couple seconds, not falling down/pass out, but that she cant see.