Hi Miss Bird,
I’m in the UK too. You’re among friends here, we understand your suffering and the many frustrations of having this ‘hidden’ illness.
My cerebellar tonsils were not herniated 5mm either, so I was diagnosed with ‘low-lying cerebellar tonsils’, by the Chiari Institute in New York, where I had to travel to in order to get a full diagnosis. This level of ‘cerebellar ectopia’ is also sometimes referred to as ‘Chiari 0’ and can be just as problematic, especially if as Diana says, they form a ‘bung’ between the head and spine.
I would also ask your neurologist to be more specific and clarify what he meant by your CSF being ok, had he done a ‘Cine MRI’ to prove that the flow was not restricted in any way? I had this done in New York and it showed a diminished flow.