Advanced Imaging of Chiari I Malformations

Chiari type I malformation (CM I), characterized by descent of part of the cerebellum and brain stem through the foramen magnum, is a relatively common imaging diagnosis with a reported incidence of 1–3. 6% in children undergoing magnetic resonance imaging (MRI). Standard MRI sequences can establish the diagnosis of CM I rather easily. However, it remains neither sensitive nor specific for predicting symptoms and disease severity and does not contribute to prediction of postoperative success. The development of advanced MRI sequences and techniques has expanded the role of MRI in CM I disease assessment. Advanced imaging including cerebrospinal fluid (CSF) flow studies, cine cerebellar tonsillar motion, diffusion tensor imaging (DTI), and quantitative volumetrics of the posterior fossa and biometrics of the skull base have expanded our understanding of CM I disease pathophysiology, assessment of disease severity, and alterations in CSF flow dynamics, and in certain cases aid in selecting surgical candidates. The goal of this chapter is to review in detail established MR advanced imaging techniques such as CSF flow studies and cine cerebellar tonsillar motion in the diagnosis of CM I while introducing emerging techniques in the assessment of CM I such as DTI and volumetry of the posterior fossa.