What would cause migraines weeks after a motor vehicle accident?

Headaches auto accid: Post traumatic headaches are quite common and will go away after few weeks and are not serious but it is well documented that some headaches will persist and some have clinical features of megraine and have to be treated successfullly with anti migraine meds, why it happens is not known.Although we know regular headaches may be due to neck injury, or post traumatic headaches.

Brain & Nerves: Following a motor vehicle collision, the soft tissues (muscles, ligaments, tendons, discs) and sometimes nerves and event the brain. 80% of headaches are referred from the neck. The brain can be irritated and migraine like symptoms are common. Monitor these symptoms closely and tell your doctor about them upon each visit, particularly if they worsen.