Introduction: It has been well documented that Chiari Malformation type I (CMI) is associated with smaller PCF and altered CSF flow dynamics. This project determines the association between morphology and hydrodynamics in the same patient cohort. An atlas based automated PCF volumetry (1) was applied to assess PCF volumetry and determine association with CSF and blood flow measurements obtained with phase contrast MRI (PCMRI) (2)

Methods: PCF, hindbrain, and 4th ventricule volumes were obtained in 36 CMI subjects (8M:28F, 37±11 years) and in 37 matched healthy subjects (13M:24F, 36±12 years) using high resolution 3D-T1W MR images. Cranio-spinal CSF flow, blood flow, and cord dynamics at C2 level were quantified using CINE PCMRI. CSF stroke volume, maximal cord displacement and MRI derived intracranial compliance and pressure (MRICP) were derived. The CMI group is further divided into “typical” and “atypical” based on symptomatology.

Results: Statistically significant differences in PCF volumetry were found between the control and CMI cohorts for the following measures; PCF volume of 211±16 vs. 184±19mL (p<0.0001), PCF crowdedness (hindbrain volume normalized with PCFV) of 0.79±0.036 vs. 0.88±0.038 (p<0.00001), 4th ventricle volume of 2.19±0.69 vs. 1.43±0.48mL (p<0.0001), respectively. The corresponding hydrodynamic and dynamic measures that were strongly different in these two cohorts were; maximal cord displacement at C2 of 174±47 vs. 373±198 µm (P<0.0001), and MRICP of 8.5±2.2 vs, 11.6±6.1mmHg (p=0.007), respectively. The differences in the above measures for the “typical” CMI group had stronger significance (smaller p-value) compared to “atypical” group.

Conclusions: Automated measurements of PCF volume, 4th ventricle volume are significantly smaller in CMI, while PCF “crowdedness” is higher compared with controls. This parameteres in CMI are associated with larger maximal cord displacement during the cardiac cycle and MR-derived value of ICP. Therefore combing PCF morphology with CSF dynamics provide stronger quantitative and objective classification of CMI.

Patient Care: It will improve diagnosis accuracy of CMI patients

Learning Objectives: Demonstrate the association between PCF morphology and CSF dynamic alterations in CMI.

References: 1. Bagci AM, Lee SH, Nagornaya N, Green BA, Alperin N. Automated Posterior Cranial Fossa Volumetry by MRI: Applications to Chiari Malformation Type I. AJNR Am J Neuroradiol. 2013 Mar 14 2 Alperin N, Sivaramakrishnan A, Lichtor T, Magnetic resonance imaging-based measurements of cerebrospinal fluid and blood flow as indicators of intracranial compliance in patients with Chiari malformation, Journal of Neurosurgery, 103(1):46-52. 2005