If you were looking at the back of my head divide it into quarters. Most of my headaches are in the bottom left quarter. Tension, poor posture, neck and shoulder pain, cold and dampness can cause them. Also other people including myself have problems with light causing headaches. Flourescent lighting sometimes, but my big one is headlights, especially those awful blue colored ones and any cobalt blue lights.......it's like a knife stabbing me behind my eye. I wear the eyeglasses that adjust to how bright it is and also an antiglare coating. They are wonderful, it's so much better than taking sunglasses on and off. The pain starts from the base of my skull and behind my eye and my temple hurts. The occipital nerve, not optic nerve is what causes my headaches. Usually that pain is referred pain from elsewhere. Mine is from nerve entrapment that starts from my left shoulder joint and up to my neck and head. Migraine medications do not help headaches from nerve entrapment. I have 2 elcectrodes in my head hooked to a stimulator. I have it on all the time. It has taken away 80% of my headaches, I used to have them 24-7. If I wake up with a headache starting at the skull base and it goes from there and goes all the way around to my forehead I'm doomed. This doesn't happen very often, but when it does I take morphine, nausea medicine, pack my head in ice and sip hot jello to help with the nausea. (They use hot jello for cancer patients to help with chemo nausea. Put 2 or 3 tablespoons of jello in a cup and pour in hot water from your teapot. Sip it hot. I sort of coats your stomach and it really does help no matter how wierd it sounds. I have fibromyalgia,which does not cause swelling, but I also have myofascial disease that does. Fibro and myofascial diseases are not the same, they are 2 separate diseases. I just started a thread yesterday called Ablations and Stimulators. I'm sharing some things that I have had done to me. Perhaps you may find it useful.
I hope that this has helped you some.