Automated Volumetric Measurements of Posterior Cranial Fossa by MRI: Applications to Chiari I Malformation

Noam Alperin¹, Snag Lee¹, Derek Monette¹, Ahmet Bagci¹, Birgit Ertl-Wagner², Raymond Sekula³

The diagnosis of Chiari Malformations type I (CMI) is based on tonsillar herniation of 5 mm or more below foreman magnum. However, this criterion is poorly correlated with symptoms severity or outcome. The size of the posterior cranial fossa (PCF) has been shown to be a more sensitive marker for CMI. Currently there is no reliable method for volumetric assessment of the PCF. An automated method for measurements of PCF and hindbrain tissue volumes has been developed and applied to CMI. Results demonstrate, for the first time, that in addition to smaller PCF, CMI is also associated with a smaller 4th ventricle.