If you ever had a bump, hit, car accident or fall to the head or shoulders it's a possibility.

here's more info about it
Chiropractic care info- a good one can help with many symptoms:
http://www.upcspine.com/self.htm
http://www.uppercervical.org/subpag...b/about_faq.php
http://www.spineuniverse.com/index.html
http://www.coloradochiropractic.org/.../glossary.html

It helps me, I was all uneven LOL