Autonomic Seizures.... anyone with experience? (LONG)

For several years my DH has been plagued by what we've termed as "dizzy spells". They first started happening about a month after he got a big promotion at work. At the time they started, he had been on a stimulant for ADHD for about 18 months. About 6 months after they started, he had an episode while driving and actually passed out briefly, coming to a halt on the opposite side of the road (thankfully, no one got hurt, and just a few scratches on his car). A few days later, he went through a variety of tests to determine the cause of these episodes: brain MRI, EEG, cardiac stress test, 24-hour Holter monitor, EKG, complete blood panel, tilt table testing. His ADHD meds were suspected after he failed his first tilt table test. He retook the test after a 1 week med wash and passed with no problem. So the docs decided it was the ADHD meds that caused the spells. He went off the meds completely, and then the spells started happening again a few months later. He then went to see his GP, who thought that the spells were due to anxiety as they resemble panic attacks. The symptoms are: a gradual feeling of light-headedness, dizziness, nausea, skin flushing, sweating, a feeling as if he needs to move his bowels, intestinal noise and gas. He's had these episodes in a variety of places and times of day, no rhyme or reason: airports, sitting at his desk reading email, reading a magazine, in meetings, lying down in bed, after using the toilet, on the train, while driving, after sports, in stores. He has to stop what he's doing and steady himself, usually with his eyes closed and his head bent over. He does not lose consciousness (except for the one time in the car). He has be rx'd Paxil for the suspected panic attacks, and is now at 40mg. In the past few days he's had about a dozen "attacks", from mild/moderate to severe, some of which I witnessed. He became tired and felt poorly after having a few of them in a short perio of time (hour or so). After some further reading, his symptoms sound very much like an autonomic seizure, and with his lack of "cure" with the Paxil, I'm beginning to wonder if there's more to this problem. Thanks in advance for the feedback.