My DS has a 55 point gap between his highest score (visual spatial) and his dismal processing. DYSDD has a 46 point gap between her verbal comprehension and processing. His low processing score seems to be linked to his reading struggles as well-his rapid naming ability is likewise very low. DD is a great reader but both have dysgraphia and CAPD. DS has ADHD but DD does not.
I would say, based on my limited experience, that the big gap means explore all possible LDs that you might suspect. If your kid is very bright he will likely be able to compensate for hidden LDs for a while but at great cost to himself. Don't depend on the school or his teacher to be able to help. They are not great at seeing deficits and struggles in smart kids (except ADHD which seems to be the reflexive answer for everything) or conversely, see intelligence in a kid with LDs that is struggling!
Pick up "The Mislabeled Child" by Eide and Eide. With the brain injury you describe, brain-based systems that affect learning (visual and auditory processing) could easily be impaired. These deficits are subtle but very impactful for learning and commonly confused with ADHD.
