Sudden change of behaviour.

My parents cat is 10 years old and has numerous changed behaviours. He wont be held anymore, he sticks his claws in now. Has always been a lap cat. He wont go outside. He will only go in the dining room and kitchen. Will not go upstairs or in the living room and now stays like this all day. It looks goofy but I'm scared it could be neurological. 

What an interesting posture!   I cannot say for sure why he prefers this one, but my short answer is that I wonder whether he may be avoiding pain. More waffle to follow.

It is now well understood that dogs and cats evolved differently from one another.  Both cats and dogs will communicate when they are in pain, but cats seem to be much more subtle about it.  Indeed, it was assumed for years that cats didn't feel pain as strongly as dogs, but we know think this to be untrue.  Rather, the signs of pain in a cat are more subtle.  Here you describe a reduction in exercise and an unusual lying posture;  I do wonder whether chronic (low-level, ongoing) pain might be implicated here?  I wonder if it's possible that this posture stretches the belly (for example, to provide relief in pancreatitis), or takes weight of certain joints?  I'm sure you'd have mentioned it had you suspected pain, but it is normal for cats to hide that they are in pain from their owners.  This is only a theory - there may be other explanations.  We do recommend that you take this beauty to the vets, not only so that they can admire him (did I mention that he is beautiful), but because they might want to examine him to do tests.   Please do let us know how you get on.

(EDITED FOR SPELLING AND CLARITY)   It is now well understood that dogs and cats evolved differently from one another.  Both animals will communicate when they are in pain, but cats seem to be much more subtle about it, to the extent that it was assumed for years that cats didn't feel pain as strongly as dogs.  Here you describe a reduction in exercise and an unusual lying posture;  I do wonder whether chronic (low-level, ongoing) pain might be implicated.  It is possible that this posture stretches the belly (for example, to provide relief in pancreatitis), or takes weight from certain joints.  This is only a theory - there may be other explanations.  We do recommend that you take this beauty to the vets, not only so that they can admire him (did I mention that he is beautiful), but because they might want to examine him to do tests.   Please do let us know how you get on.