I’m so sorry you are dealing with this! This is Chiari, certainly. What I found is that high intracranial pressure can worsen Chiari AND can mimic Chiari. My children and I were able to avoid invasive surgery by treating the high intracranial pressure (that wasn’t evident on the MRI). This is all explained in The Driscoll Theory book. Do you have it? Please keep us posted! Love, Dr. D