by a sudden increase in barometric
pressure from crossing over a
high mountain pass. After that, every time the air pressure would drop suddenly from weather changes(frequent here in Western WA), his face/head pain would start like a cluster headache with his upper molars aching on one side, then the facial nerve would get involved and he'd have trigeminal neuralgia, tinnitis, one eye would blur, and he often lost the hearing in one ear. And then the global head pain would come on.