When he said it was internal he inferred that there was nothing he could do. It seems permanent but I'm really not sure if anything can be done. For me, it becomes more pronounced at times, indicating what I call a migraine, but the pain is more of an irritant, everything gets mixed up and my work suffers. Luckily, it does not happen often and I take a sick day. Stress triggers the ocular migraines I get and I'm better at controlling the stress. No flashes, but black spots I got too! My doctor at the time called them 'floaters' and she said it was common. As far as I know, nothing can be done. Perhaps someone else can provide more information... back then PCS was not a recognized ailment.
Jamie