Over the past couple of years I have developed these spasms/twitches. They usually only affect my upper body. I get stiff, my eyes roll back and I jerk or twitch backwards. Sometimes its just a once or twice thing, then sometimes it can last for a few seconds. My arms tend to lock up in a bent position as well. On occasion, it will make my knees give out the same time my upper body twitches backwards and I lose my balance. Nothing in my life has really changed since before I have developed these spasms. They are not an everday occurance, either. But it does seem to be worse when I'm tired or haven't had much sleep. Could they just be stressed related? They are not painful, just very embarassing.