Blooming subarachnoid space anterior frontal lobe indicate leptomeningeal siderosis?

[Cuzbel]

My son had a bad fall resulting in concussion and seizure at a skate park about 18 months ago and then a fairly small stack on his dirt bike resulting in another concussion about 10 months ago.  The first incident he was discharged within 7 hours and the second he was in hospital (a different one) for four days for observation.  We pushed for the last 18 months for further tests as a CT both times had come up clear and finally we were referred to a brain injury specialist who ordered an MRI, some of the findings are referenced in my question above.  Just trying to understand what this will mean for him now and in the future, he is only 16.