Chris,
Upper neck injuries are very common with concussions. The doctors often over-look them.
There is a special chiropractic skill called Upper Cervical Chiropractic. Check out
www.nucca.org and
www.atlasorthagonality.com
Be very careful with chiros who do the "twist the head and pop the neck" adjustments. They are often to aggressive for the upper cervical injuries.
Some physical therapist can help with gentle traction and manual manipulations.
With any upper neck treatments, be sure to ice the area after.
My best to you.