I just want to say (and I really hope that I don't come across as intruding!) that I do not suffer PTSD. However, most of the people that I care deeply about have it, or some other similar story.
I've just finished my first year at university, and from about the second week in I ended up spending most of my time with this guy, funny, intelligent, gentle. Anyway, within a couple of months I saw one of the scariest things happen to him - one night he started passing out, and woke up not knowing who I was, terrified of me. He was crying out whilst being unconscious, thrashing around. The next day when I tried to tell him what had happened, he ended up passing out again, so in desperation I asked him what he wanted me to do - whether he wanted me to tell him or if he wanted me to stop. He asked me to stop, and so I did.
Anyway, it happened again a couple of weeks later, then the term ended and we had no contact over Christmas because I was in Australia.
Second term, things intensified. We got together in a relationship which lasted 6 days, but although we ended within days we still ended up spending nearly every waking moment together. And the blackouts continued. I now know them to be flashbacks, regression, reliving what his parents put him through.
Now it's almost script. I know when he's likely to black out. I know most of his triggers - alcohol being one of them (seems to bring to the forefront memories he's not yet ready to deal with?) I know whether I'll be able to distract him and avert an 'episode', I know when it's too late for distraction and the only thing to do is try and get him to his room before it hits (I've tried to keep them as private as possible for him so he can keep up a 'normal' act around everyone else, especially as being a young male, he felt embaressed that he would become so vulnerable around me) I know now how to keep him calmer and make the 'episodes' pass quicker.
All I'm saying, is that I am deeply involved with this guy (we ended up dating again, breaking up for the summer, but the way talk has been going there's still the desire to be together) and every time he feels bad, and most of the times he's passed out or in in between blackouts, he calls me.
Even if we don't work out as a couple, we're still going to be best friends. But I need to make sure he's as comfortable and safe as possible. The problem is, when all this started I had no idea what to do.
I completely appreciate the need to keep it private, and the trust issues such a person must have. If there was any way I could stop him from suffering, any way i could do as he's begged me on several occasions and 'make them go away', I would.
But I can't, and I know I can't, all I can do is stand there by him and make sure he knows he always has someone he can lean on when he needs to.
I'm just worried that I might make a mistake. When it first started happening I didn't understand what was going on, so when he somehow ended up telling me during a blackout that I was a 'grown-up' and I told him he was my age and I was XXX he told me not to be silly, that would make it 2006. When I told him it was 2007 he freaked out. Another time he caught site of himself in his mirror thinking he was 11. He passed out on the spot and I managed to catch him before he hit the floor and carry him back to his bed, but I guess what I'm trying to say is that if he had told me what was going on beforehand, I wouldn't have been so terrified for him, I would have been able to prepare a little, I would have known how to help him better.
Now I know (mostly) what to do - play along and talk about old tv shows and comic books when he thinks he's a lot younger than he really is...I know he wont remember most of it the next day but my reasoning is to keep him as calm and fear-free as possible which will (hopefully) make the blackouts pass quicker and enable him to go to sleep quicker.
He lost the ability to speak a few times as well, and again, I didn't know whether or not I should be calling the ambulance. He couldn't tell me what to do at the time - he was scared and angry and at once trying to make me understand and trying to pass it off as just a fluke.
I do understand the need for privacy.
I'm just saying that there are mistakes I made in trying to help him, and if he had told me some things beforehand, I could have averted those mistakes.

He's still in the stage where he has considered that he has PTSD but hasn't fully accepted it yet. Which means there are questions which I have, but don't want to ask him because he's not ready yet.
This may be in the wrong place on these forums, but I just...I feel very strongly about this, and I want to be able to help him as best as I can (him, and it seems about 4 of my other closest friends with similar stories) so, as the question was about how much to tell partners, I would ask that you tell as much as you feel comfortable with.
Trust me, they'll be scared and not know how to help you and protect you, and the more they know, the better they can help. The less triggers they end up standing on because they know where they are. I know to keep my hands in sight, I know that bright lights hurt his eyes after an episode, loads of other things I just know now, that I had to work out by trial and error.
So from someone who is experianceing this from the other side, as it were, I am so sorry. I will never fully understand what he has been through, but I'm trying my best to understand, to help him through this.
He recently told me that he trusts me more than anyone he has ever known before, which means so much to me as I know how low his trust capacity is.
It's been terrible, it's been so hard thus far, but whatever else happens, I'm staying by his side and if it's the last thing I witness, he will be okay.
I just need to know if there's anything I'm doing wrong, if there's any more I can do, and I felt this thread was relevant for me. I understand that there are things he will never tell me, and every question I do ask I preface it with the words 'tell me to back off if you don't want to answer'.
I just hope that he will tell me if there's anything more I can do to help, and I wanted to say it's difficult to know what to do, difficult for the people who have to watch the people they love go through this internal battle and they don't know if a move from them will make it better or worse. Sometimes the same damn move which works and makes things better for some stages makes other stages worse.

I hope I made sense there.
XOX