Sll, Welcome! Screaming is allowed here. I do not think the radiation is cause for any "brain" problems. Generally they avoid nuking the brain. The whole process is very taxing on the mind as you have found (it seems) for yourself.

His post treatment side (after) effects sound quite normal and he was treated at one of the best places in the U.S.

My humble suggestion is that you get him active and then wait for a few more weeks to see improvement.

Take care of yourself as well

Mark, 21 Year survivor, SCC right tonsil, 3 nodes positive, one with extra-capsular spread. I never asked what stage (would have scared me anyway) Right side tonsillectomy, radical neck dissection right side, maximum radiation to both sides, no chemo, no PEG, age 40 when diagnosed.