How did my elderly mouse die?

Question
Hi Natasha,
I went to feed my mouse yesterday, and she was in her house not moving. I picked her up and she barely responded. I then spent the next few hours trying to get her to eat/move/drink. Eventually, she started to eat, but then I noticed how strange she was acting. She would shake terribly while walking, her teeth chattered, and it would sometimes seem like she was trying to vomit. Aside from this, she tried to walk around and play on her wheel, but her shaking was really bad. I put her in her house again before I went to bed, and this morning found her out of her house lying on her side, dying. I gave her some cotton and laid her back in her house, and sadly she is now dead. Her name was Baby, and I believe she was about 3 years old. She was fine a few days ago and I just don't know what happened. My question is what caused the shaking and odd behavior, and if it was a stroke or old age or something that killed her. Thanks.
-Joy

Answer
Dear Joy,

3 years is a very long time for a mouse to live.  In fact it's incredible.  2 1/2 years is usually about the limit.  So she was very, very old.  Lots of things can go wrong, just like with people-- heart attack, stroke, kidney failure, etc.  The aging process itself is also very quick.  A mouse can go from middle-aged to very elderly in a matter of days.  It will suddenly be shaky or heaving, hunched over, with rough, unkempt fur, and have a hard time with normal activities such as walking or eating.  Although some mice can go on for months in this state, others die within a week.  It sounds like Baby went a little more quickly than that, though, so something probably did happen to her.  

My condolences for your loss.

squeaks,

Natasha