Hmmm, a few more questions and you don't have to answer them if you don't feel comfortable. Just trying to gain some insight ...

1. Do you have a history of childhood trauma (abuse)?

2. Just prior to an "episode," do you have any recollection that anything stressful was happening that may have "told" your brain to check out for a while as a means of coping.

3. I believe I remember you saying you've had these symptoms for over 50 years, have they progressed since the onset?

4. And what was the age you remember having your first episode?

Obviously your brain is taking a vacation when this happens but you need to figure out if it's physiological or psychological. Sounds like you've had a lot of tests but have you spoken with a therapist. He/She may be able to shed some light on the situation??

Good luck and keep us posted.