From what I understand (I was just finally diagnosed with PCS and silent migraines yesterday .....had my injury in 2003 and found NUCCA chiropractic that helped get my life back....until now when I have another concussion...)
anyway, silent migraines are ones without headaches. They can mimic symptoms as severe as a stroke. They can also mimic panic-like symptoms, dizziness, etc.
I have been trying to read up on it, as it's been like having them every day for me (maybe even multiple times a day). Even after I felt better with my NUCCA treatment, some of the lingering symptoms of PCS that I had were anxiety and lightheadedness. I found when I didn't sleep enough, drank caffeine or alcohol, menstruation and sometimes unexplained reasons the anxiety or lightheadedness reared it's ugly head. Maybe that was the silent migraines?
I tried to post a link here but it won't let me, try and google silent migraines there will be a better explanation than what I'm giving.