Night terrors, I know them well. They're very scary. But not so bad when you know what's going on and what to do.
In May, 2006, my two little granddaughters came to live with me. The older one, 2 1/2 at the time, started almost immediately "waking up" screaming or crying, within about 10 days. This lasted for about 6 or 7 weeks, and then pretty much stopped, with only 2 occurences since.
Fast forward - my little granddaughter is 2 1/2 now, and she's had a few of them. Hers are shorter, less frequent, and alot easier to deal with than her sister's were. However, I've twice walked into her room to find her standing on her bed, trying to hold onto the wall.
They are caused by a couple of things. Stress, or a traumatic experience, can cause it. She had gone thru the trauma of being taken out of her mother's care and placed in mine. Fatigue is a big cause, so is potty training, and so is an unfamiliar surrounding.
What's happening to the child? They are stuck between two stages of sleep, and their body just doesn't know how to "get out". They are possibly "seeing" monsters (this is NOT the same as a nightmare) or other scary things.
What to do? The first couple times it happened, I tried to comfort her, of course. But when it kept happening, and it would last for up to 20 minutes, and there was NO comforting her during it, I knew it was time to find out what was really going on. When it happens, do not try to console the child, as this could very well make it more intense. If they are seeing monsters, then when they see you, they do not recognize you as you, but you could actually be one of the monsters. So what to do? Just make sure the child is safe, will not hurt him/herself in the surroundings, and just sit patiently and wait it out. I ended up sitting on the floor, in front of her chest of drawers or in the doorway, and waited it out. Sometimes she did wake up afterwards, and when she saw me, she would acknowledge my presence, calmly, and I knew it was over. She'd fall asleep again.
What else to do? Make sure they get plenty of rest, and have a normal bedtime routine. Make sure there is nothing in their bedroom (i.e. toys on the floor, etc.) that could hurt them if they get out of bed.
Night terrors are not the same as nightmares. The child will not remember them in the morning, whereas they will remember a nightmare. They're similar to sleepwalking, actually, in that the brain is stuck between the two sleep stages there as well. Recent studies have shown that this is why bedwetting happens as well.
It is very scary when you witness a night terror. Just keep in mind that it's very common, and it's a phase that WILL be outgrown.