Becky from ChiariConnectionInternational (yahoo group) says:
“My daughter has a small Chiari 4mm. But according to Dr. Frim has brainstem compression. So if I understood him correctly flow doesn’t matter if you have pressure on your brainstem.”
So, as I understand it, you can also have what looks like normal CSF flow but, still experience symptoms, due to the rogue cerebellar tonsil pressing against the brainstem.