What Could Be Causing Severe Upper Neck Pain And The Inability To Open The Mouth Fully Despite Steroids?

My wife is experiencing upper cervical pain and has had x-rays and an MRI in the past week. She is having trouble opening her mouth fully to eat. Our pain management doctor put her on a oral steroid regimen of which she in the 4th day of taking with very little improvement in pain level. He said there is some arthritic damage to that area but nothing that would cause the mouth issue. He feels there is something other than the cervical issue causing this. We visited an emergency room on 10/10/18 where they did an x-ray and gave her a 10 day supply of Ativan.
The pain Dr. said we should revisit the ER and have further testing done.
We also had flu shots on 10/2/18. My wife is 75 years of age.