My daughter has these episodes where she sleeps for about 16 hours and is unable to be roused. She is very lethargic and she only sits up to vomit. Her vomit is very thick, foamy and yellowish. After she vomits she lays down and goes directly to sleep again. She doesn't eat or drink during this time. After about 14-16 hours she awakens and resumes normal activity. These episodes come and go about every 3-6 months. Please help no one can give us answers and we are scared.