I was told by my doctor that I have what she believes low lying cerebellar tonsils and it was at 4mm,shes referred me to a neurologist which I seen in a week.... I've read on some websites that Chiari was anything 3mm and more, and some websites I've read where it was 5mm or more... I was in a car wreck where I suffered head trauma and that was 9 years and for the past 2 years I've had horrible headaches, memory problems, so I was wondering if what I have is considered Chiari Malformation