Our Jess was a Border Terrier and at 14.1/2 years old she sadly expired and had been diagnosed with a brain tumour which explained her doing out of character stuff and becoming increasingly deaf and blind. She was still game for walks right to the end but they were shorter than when she was young. She was not as agile at styles and gates but managed ok.
The signs were of a gradual decline up until the last 4-5 months then the tumour made her do daft stuff like pee in the house after a walk and she would just wander off if left off the lead, at her age, the treatment sounded a bit tough and the prognosis not good so it was hard to say goodbye to a faithful old friend, but was the kindest thing to do. With Borders you never got any indication they might be in pain... She was hard as coffin nails. In her days she had crested every peak in the Lake District and a number of Munroes. We were often asked " how did she get up here?"
Very sadly missed...