I contacted a friend whose son has had troubles after playing sports that resulted in many concussions. Here is her information and she hopes it helps your son.
Our son has had several concussions and I have researched the following options. It is possible that you could try the non-medicinal route of acupuncture. I have researched this and it is reported to help with headaches. Does your son have any learning difficulties after his last concussion? We found that the company Learning Rx is wonderful–it even helps veterans who have suffered Traumatic Brain Injury. It certainly helped one of our children overcome a memory problem. Just be sure to ask for a Master Trainer, for the best results. This company provides trainers who work one-on-one to do mind exercises/puzzles often with a metronome, to take advantage of brain plasticity to build new neuronal pathways. If that is too expensive, and if I recall it is about $3,500-4,000 for the first full program of about 6 months, then another options might be Luminosity.com. I believe that is $15.00/month.(You can see if there is a Learning Rx franchise in your area by going to their web site.)
I so very much hope this is helpful.
(Also her son stopped the two sports where he had suffered the concussions.)
We wish you and your son all the best. It is so difficult when we see those we love suffering and we aren’t receiving help/treatment from the MDs. We will keep you in our prayers.