When reading this please bear in mind that it's my best guess based upon (training and clinical experience) but consider the response in the context of the limited information you've given.
Yes and no.
Besides me, I know two people who can do that maneuver. That doesn't mean there are only three, just that I haven't met more. A few old-timer chiros use a technique called Biocranial technique (BCT). I have no idea how difficult findinf a practitioner would be. There are a few more adjustments that accomplish similar results but do not stretch the ligamentum nuchae.
A brainstem herniation would cause complete respiratory failure. That being said, the cerebellar floccus can partially herniate and cause a lot of symptoms which mimmick other diseases, including fibromyalgia. If that was the case, only a mild case would respond to chiropractic care, I would do BCT and neutral traction. neutral traction, neutal traction, neutral traction......... neutral traction. Did I say neutral traction? Flexed traction would work as well.
The herniation is slight but can be seen on MRI by an expert. Typically it starts with diffuse pain, facial weakness, rash, upper arm/hand weakness and tender points in the forarms and legs, and a loss of energy.
Remember, that is essentially a guess based on very little information. If all else fails you can try catching me on the cell later tonight. If you want the number PM me.
Jake