Hi and welcome,
Unfortunately you haven't provided enough information for anyone to even try to explain what your brain MRI findings could be meaning.
What i can tell you is that the pons is small, approx 2.5cm but it's a major structure in the upper part of your brainstem, it's basically a bridge between various parts of the nervous system.
The corpus callosum is a thick band of nerve fibers, approx 10cm, it's kind of a 'C' shape, it's located between the two hemispheres and connects the left and right sides of the brain, basically allowing both side of the hemispheres to communicate with each other.
Hope that helps a little........JJ