But the movie gives us several hints that Leonard's condition may be more a product of his own psychosis than anything else. They really blur the line a lot between Leonard and Sammy Jankis, almost to the point where you question whether or not this Sammy guy ever really existed, or he was just conjured up for Leonard to deal with his own problem.

Which wouldn't bother me. I think it adds extra dimension to that whole 'unreliable narrator' thing that Memento had going on. Not only is his memory whacked, but he might very well be a full-blown nutcase. For all we know Leonard's wife is alive and well somewhere (that or her cause of death was actually an insulin overdose)

So I guess I don't find it farfetched that Leonard knows he has this condition... since I kind of buy into the theory that he sort of created the condition to begin with.