Hello and thanks for researching this very important question!
Dogs can develop a number of neurologic side effects from illnesses such as hypothyroidism, liver or kidney disease, Cushings Disease and diabetes.
There is now what we are coming to know as a kind of dog senility called "Canine Cognitive Dysfunction". Symptoms include loss of attention to familiar people, failure to concentrate, difficulty with holding urine or stool, and other strange behaviors such as standing in a corner all day, going to the food dish and not eating, or getting "lost" in familiar surroundings. Symptoms are often worse at night, some dogs even switch their entire day-night schedule or cry all night.
This condition seems to be caused by a decrease in a brain hormone and can be treated by giving a medication called L-deprenyl (the brand name Anipryl is quite expensive, but the human generic "selegiline" is very affordable). This condition is progressive and worsens over time; treatment can reverse early signs and slow down the damage so that a dog can live a more normal geriatric life.
**I do recommend that you have this dear pet examined by your veterinarian so that you can get to the bottom of this situation as soon as possible. If this condition, or some other illness is to blame, then time may be of the essence.***
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