Is it the case that brain-injured children also suffer from severe physical disabilities as well?

Very much so. It is rare for children to be severely brain-injured but not physically affected. The brain controls everything we do - our entire nervous system. When it is injured, it can't exercise that control properly. Most brain-injured children can't walk, and their basic motor skills are very impaired. For some, picking up a pencil or a spoon, or turning a page in book. requires huge effort. For many, these things are impossible.