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Yes, you should insist on a scan - preferably MRI brain with contrast. The depression and other cognitive symptoms seem to have evolved after the head injury and hence a traumatic brain injury has to be ruled out. The change in character - from kind to heartless and mean, lack of emotions could be due to a injury in the frontal lobe.
Other symptoms including the depressive symptoms does not fit into a traumatic brain injury or post concussion syndrome. But still there is a probability that these are related to the past injury and so it has to be ruled out by taking an MRI.
Does he have any other behavioural symptoms ? Any change in urination pattern (like urinating in public ?), lack of inhibition in general ? lack of smell etc ?
Hope this helps