057. Amplified Magnetic Resonance Imaging: Putting the "Jiggle" in Chiari Malformations

Authors: Daphne Li, MD

Characterization of Chiari malformation (CM) on standard MRI sequences does not always correlate clearly with clinical findings or outcomes. We studied a novel technique called “amplified MRI” (aMRI) to visualize the dynamic motion of the cerebellar tonsils and brainstem in pediatric patients with CM Type I (CM1). aMRI amplifies spatial variations and deformations in arteries and brain parenchyma, enabling visualization of barely perceptible motion in brain tissue induced by cardiac pulsatility.Methods: We performed a retrospective review of a pediatric cohort with CM1 and control patients. Mid-sagittal, cardiac-gated, cine MRI sequences were retrospectively motion-amplified and independently reviewed by 4 blinded observers, assigning a numerical grade (0 = no motion; 4 = maximal motion) for overall, vertical, and horizontal motion. Patient data was reviewed for relevant clinical data.
aMRI sequences and clinical data were analyzed for 13 children (n=8 CM1, n=5 control). Average patient age was 6.49 years (CM1: 7.3 (range: 2.7-14.8), control: 5.1 (range: 1.2-18.1)). The most common symptom was headache (n=4), while others included incoordination, dysphagia, snoring, numbness or tingling. Two of eight CM1 patients were asymptomatic, two had syrinxes, and four underwent Chiari decompression. Overall graded motion on aMRI was significantly higher in CM1 patients versus controls (p=0.001), especially in the vertical plane (p=0.015). No significant correlation was noted in overall motion in patients without a syrinx, however, more vertical than horizontal motion was visualized in the presence of a syrinx (p=0.019). On univariate analysis, patient age was inversely correlated with motion visualized on aMRI. Other factors, such as symptomatology, gender, need for intervention, did not correlate significantly with any differences in motion.
CM1 patients were observed to have significantly more motion on aMRI. A larger cohort is currently under review to correlate the radiographic and clinical findings and further define the clinical implications of this novel MRI technique.