Hi there, unfortunately your question has landed in the MS community and our MRI understandings is generally centred on MRI's relating to MS or similar....
Personally, I do understand how frightening it can be when your young son is strangely staring and isn't responding to any of your attempts to get his attention.........my son did this not long after being diagnosed with Asperger Syndrome (Autistic Spectrum Disorder) and he also went through getting an MRI to rule out brain damage, epilepsy etc.
I will request your question be placed in a more appropriate community for you but for what it's worth, my understanding of what your son's MRI report concludes, is basically that there wasn't any abnormality discovered and i think your paediatric neurologist is worth believing.
Hugs...........JJ