Dogs do get dementia, or "old dog disease", but I wouldn't undertake to diagnose it myself;

I'd take the dog to the vet.

At 11, she may have a kidney or bladder problem.

better to *know* for sure.

If she does have CCD (Canine Cognitive Dysfunction), there is a medication that may be helpful. But you will need to get the dog to a vet for proper diagnosis and treatment.

Laurie

Yeah, I am not qualified to have an opinion about terriers (lol), but 11 seems a tad young for it to me. Larger dogs (I have Australian Shepherds) seem to go till about 13, and smaller usually last longer (general rule).

I agree with the others that she first needs to have a thorough physical by the vet. I don't see anything in your post that would make me think the dog has dementia but I do have some questions. Does she have access to the outdoors while in the garage or is she still dependent on you to go outside? Is there anything in the house (or going on in the house) that is causing her to prefer staying in the garage vs the house?
How often is she exercised and how often is she taken outdoors (if she relies on you to open the door)? Keep in mind that, like humans, dogs often need to go out more often as they age so be prepared to either take her out every couple of hours or give her easy access to the yard.
Also......observe you dog and see if she moves as though she is stiff and/or sore. She may be dealing with arthritis, but this is something that a vet can also help you with.
IMO, it sounds as though medical treatment and other changes may be all she needs.

The following is a group you can subscribe to and chat with others that own the breed. They may have more input.......Yahoo Group