"Congrats on your first HM! Think you'll do another? "
Hopefully, I am entered in the same one again next year. 
I had a serious bicycle wreck in early August including a Class III concussion (I was out for over an hour) Bike helmets can definitely help prevent catastrophic head injuries but they don't do much to reduce the likihood of a concussion. Long story short, while I was able to resume riding and running, the wooziness and headaches came back last week when I did my first run with hills - perhaps to much jarring on the descents. Anyway I am off running for at least another week. I just have to be patient (not one of my virtues) and go slow on the recovery