Is osteopathic manipulation of the spine, especially the upper cervical spine, safe?

Yes, as long as: The manipulations are done with your neck in neutral or flexed, but never extended. The only serious complications during manipulation (chiropractic or osteopathic) is when the "cracking" techniques are done with your neck in extension. Maneuvers. If you are understandably stressed, ask for more soft tissue, muscle energy and fascial, and less articulatory and they should understand and respect it.