diffuse axonal injury

hello my son recieved a head and eye injury in the school playground in October 2007. 2 kids pulled him to the ground and hit his head onto the playground tarmac. my son has autism, pda and hearing impairment and unfortunately even though the school staff found him lying motionless and unresponsive on the playground floor no one sought medical advice for him.  when he returned home he said he could not see and had a headache.  we took him to accident and emergency dept, who admitted him with head and eye injury, we were advised after optical departement did various tests the next day that his brain had hit the back of his eyes so hard that it had bruised the back of his eye, which was the reason for his loss of vision in his eye. he also had lost some accuracy of his colour vision, he had lost 3d vision and the ability for his eyes to track, he also had an alteres sense of smell and things which he previously liked or found funny he did not like or find funny anymore.

a week after the injury, his vision had not improved in his eye and further tests were arranged to test the optic nerve functioning and an mri scan of his head.  following the tests he was refered to a specialist at a different hospital who explained to us that the reason he had lost his vision was due to diffuse axonal injury at the point where his head had been hit on the ground, which is where the brain processes visual information.

his vision and functioning of his eye has now fully returned , he still suffers from migranes (migraines), his sense of smell has returned.

could anyone explain what  diffuse axonal injury is? is it likely to cause any problems in the future?

thanks