THe Central Nervous system consists of the brain and spinal cord (cervical, thoracic, and to the very upper lumbar region and may even contain the conus medularis(rest of the lumbosacral region) and even the Cauda equina within the rest of the lumbar area and in some views the optic nerve/retina and parts of the cranial nerves)--http://en.wikipedia.org/wiki/Central_nervous_system
The person who told you that was ignorant, as you obviously know and this shows the need for asking your insurance company for a physician review of your need for a cervical study by a neurologist, neurosurgeon or radiologist specializing in imaging of the nervous system for others who migh face similar situations.
More pertinent to your present needs:
Dr. Ulrich Batzdorf of UCLA (now emeritus, I think) has made syrinxes his area of special interest. I do not know if he still sees patients (he is emeritus) but last time I looked at the UCLA website it looked that way. He has trained at least one surgeon who works out of the Barrow Neurological institute (in Arizona, I think) and would at least be aware of others who shares his expertise in syrinxes and might perhaps be able to stear you their way.
As he might be emeritus and may have more time on his hands, perhaps an email to him might direct you to someone with special expertise closer by.
http://www.uclahealth.org/body.cfm?x...etail&ref=1487 contains his email address.
As you know, I rarely make any type of recommendation here as I am certainly not qualified to do so... perhaps it is our recent loss of Sheila, Christine, Chrisy and others making us all feel so helpless that encouraged me to try to help since I do have some information here ( gained from several I know having consulted with Dr. Batzdorf, although over 15 years ago)
Hope this helps.