Does the size of the malformation matter?
Traditionally, Chiari Malformation has been defined as the cerebellar tonsils descending more than 3-5mm out of the skull. However, research has shown there is no real correlation between the amount of descent (or herniation) and clinical symptoms. Some people with herniations of less than 3mm are extremely symptomatic and some people with quite large herniations are symptom free. Because of this, doctors are now focusing on whether the cerebellar tonsils block the normal flow of cerebrospinal fluid (CSF). The current theory is that disruption of CSF flow is a more important measure than the size of the herniation. Return To Top.