What Causes Blurring And Slurring Of Words?

My boyfriend has had several episodes of times where he is unable to see colors and slurring words. He is unable to process if anyone is talking to him. Most recently, he had an episode where he also lost conciousness for approximately 1 minute. His eyes rolled back, he had what appeared to be minor seizure-like symptoms. When he came to, he was disoriented for a few minutes. Each time this has happened, he started sweating profusely just moments before. Any ideas?