There is also upper cervical chiropractic , the top c1 c2 joint is a bit different than the rest of the neck/spinal and a specialized or advanced trained chiros can do that..

These websites have more details on how & what it is..
Up C Spine
symptoms list- Up C Spine - A New Approach - Sign / Symptom Checklist

National Upper Cervical Chiropractic Association - NUCCA