You said he had a neurological work up? Hmmmm.... I saw a story on Animal Planet once about an older cat a family adopted - who ended up having a sort of kitty dementia. She sometimes acted like she didn't know her family, if she left the "safe" space they made for her in the kitchen she would freeze - and cry and cry because she was "lost." It was really sad. So I would have to wonder b/c you said he seems afraid of you guys all of a sudden and hides in his carrier.http://vetmedicine.about.com/od/dise...e-dementia.htm
I see a couple of signs here in the article above.
10 Clues that Your Cat Has Dementia
1. Spatial disorientation or confusion - getting trapped in corners or forgetting the location of the litter box. House-soiling is the most common reason for referral of old cats to animal behaviouralists.
2. Altered relationships either with their owners or other pets in the household - increased attention seeking or aggression
3. Increased irritability or anxiety, or decreased response to stimuli
4. Changes in sleeping patterns
5. Inappropriate vocalisation such as loud crying at night
6. Loss of memory, such as forgetting commands or breaking house training
7. Changes in activity - aimless wandering or pacing, or reduced activity
8. Lack of interest in food, although some cats actually want more food.
9. Decreased grooming
10. Confusion about time, such as forgetting that they have just been fed
I'm not saying this is the case, but if there are no OTHER PHYSICAL problems, such as arthritis, then maybe this is something worth looking into.