It is not uncommon for PCS and upper neck injuries to overlap greatly. Some have found good help from NUCCA.org upper cervical chiropractors.

Be careful with generic chiropractors who use a twist and pop type of neck treatment. That may be too aggressive.

Sometimes, a physiatrist (Physical Medicine and Rehabilitation) may be able to help diagnose neck injuries that are complicating the PCS symptoms.

Some Physical Therapy, MD and chiro based multi-discipiline spine clinics can help with the upper neck.

I routinely suggest icing the upper neck at the base of the skull. The muscles, tendons and ligaments can become inflamed as well as the Atlas (C-1) to occipital condyle joint.

It is well worth investigating.

My best to you.