I saw your post and just wanted to add to the good advice shane and rozia gave you.
Most times docs. will decide whether or not surgery is needed based upon your symptoms - so it is important to know your symptoms. Write everything down that's bothering you, and rate it on a scale of one to ten. Then go online to some of the Chiari websites and compare your symptoms to the ones listed. This may help you determine better if it is in fact chiari causing your symptoms. Please write them down FIRST. Many people don't do this and then start creating symptoms for themselves - for instance, I never felt that my hiccups were any different than anyone elses, after reading about how chiari can cause gasping hiccups to occur more often and severly - I am convinced that I have chiari hiccups, I know this is kind of silly, but had I not read it I never would have questioned it, so be sure what your symptoms are before you begin your research.
When you are done comparing your symptoms to Chiari, check out how Syrengomyelia can affect you. Find out all you can about syrinx's and tell your NS you want an MRI of your whole spine with contrast.
Also, understand that there are other disorders out there that are thought to go hand in hand with chiari. Like fibromyalgyia and chronic fatigue syndrome, ask your doc about these.
And finally - Do Not Ignore Your Symptoms. No matter how many docs. tell you Chiari is not causing your symptoms - don't ignore them. After a while you may get to a point where you say - maybe they are right, maybe chiari is not causing my symptoms. And that may very well be the case....But SOMETHING is causing your symptoms, and you need to find out what. Healthy people don't feel "crappy" all the time. Listen to your body, and don't settle for a diagnosis that doesn't sit right with you. For years docs. told me I had migranes and panic attacks. For years I thought they were wrong, but I kept taking medications that made me sick and that I didn't need. Finally, a friend said to me - If you take meds for these disorders and you don't feel any better maybe something else is wrong. And even though I always new it I just had to hear somone else say it. I got a new doc, a new set of tests, and a new diagnosis. And I am finally starting to feel better.
Take care of yourself, and take your health seriously.
First of all see a neurosurgeon not a neurologist. All chiari hurts . find a good neurosurgoen . where do you live ?
1cm is 10 mm - roughly a 3rd of an inch, maybe as wide as your little fingernail. That may sound small, but it's a pretty large herniation coming out of the back of your skull.
Neurosurgeons often start talking seriously about surgery at around 8mm. Has anyone mentioned anything about syrinx or sryingomyelia? At a few mm's, the brain starts crowding the spine and messes with the flow of spinal fluid, In some ways, this is the most dangerous part of this malformation.
I think you need to change neurologists. I'd start checking around for Chiari specialists in your area were I you. They're kind of rare. I'm in Tennessee and I think we only have 2.