hankster, you're some diagnostician! I'll wander another way while you're thinking ...

In all the medical profiles that have been done, were there any brain scans? MRIs? I'm thinking of a slow-growing tumor or some other sort or brain changes such as white matter disease. Do you know whether he has ever suffered head injuries? Sometimes very small aneurysms can rupture causing damage but not death.

Just grasping at straws here ...