Thats exactly what my DD does when she is having one. I will wake up to her crying and i will go in there and she starts thrashing her arms if i lean over to get her she slaps me and hides in the corner of her cot. The screaming/crying is nothing i have ever heard she sounds absolutely terrified. I have learnt to leave the light off and stand next to the cot and talk in a low soothing voice. I got a referral for a sleep clinic but she hasn't had one in a while.

its horrible isnt it.