Hi there. Migraines are unrelated to injuries and they are a form of vascular headache caused by vasodilatation or enlargement of the blood vessels that causes release of chemicals from nerve fibers that coil around the large arteries of brain. Stretching of these nerves causes release of chemicals, which causes inflammation, pain and further magnification of pain. The sympathetic system is activated along with causes other associated symptoms of migraines like nausea, vomiting etc. Treatment would involve avoiding the triggers, prophylactic drugs like topiramate and treatment with triptans once the attack has begun. Consult a neurologist about the childhood head injury too as this needs to be ruled out as a culprit. Take care.
I would definietly suggest going to see a doctor with your new symptoms. To be honest, symptoms like this generally don't just pop up and then magically go away. The doctor in the mean time can at least give you something to help with the migraines. She may refer you to a specialist, such as an orthepedist or neurologist, who is more specialized in ordering tests in this area. The most likely test would be a CT or MRI which checks for any present or past tissue damage. It might also be able to tell if something is going on with the nerves involved in that area. The pain may also be partly referred from an old injury in the neck, where a lot of nerve are located. Really the doctor is only there to help, as scary as it may seem, and at this point, nothing life threatening certainly will be found. Good luck and keep us posted.
Sara RN