Hi,
If you've been riding horses much in your lifetime I suppose you've had a tumble or 2 besides this accident. Been there done that...

Something that might help is finding an expert chiropractor and one that is trained in the upper cervical adjusting technique. (aka c1,c2 or atlas /axis)

Getting the body's skeletal foundation back in optimum alignment is a good place to start.

good sites w/info on upper cervical -
www.upcspine.com
[The following Signs and Symptoms may indicate Upper Cervical (c0-c1-c2) Injury] http://www.upcspine.com/self.htm

www.nucca.com

There may be others that do the upper cervical adjusting but not a member of the nucca association.