Sorry to hear of problems with your doggy.
Unfortunately, as with humans, there's certain percentages of things that can happen in a population, both young and old.
I googled "mini-schnauzer message board" and came up with this:
http://www.google.ca/search?hl=en&q=mini-s...age+board&meta=
If you snoop around a little bit I think you could quickly tie in with some people around North America familiar with that breed who might give you some insight on this particular problem, some who have probably seen it before.
Good luck.
Cowperson