Does Brain Damage Cause Short Brain Stem?

My son had a CT scan on his brain which discovered that he had a short brain stem for his age. They later found on a MRI of his brain two small sections of brain damage. This was all done by the age of 4. He is now 6 and we have a diagnoises of DD but nothing else. Was the brain stem short because of the brain damage or are these two seperate issues all together?