Increased Hindbrain Motion in Chiari I Malformation Patients Measured Through 3D Amplified MRI (3D aMRI)

Chiari Malformation type 1 (CM-I) is a neurological disorder characterized by morphological defects including excessive cerebellar tonsillar ectopia and associated manifestations. We used 3D amplified MRI on a cohort of healthy and CM-I subjects to investigate the brain’s intrinsic motion, its association with the morphology and patient’s symptomatology, and surgical outcomes. We observed significantly higher anterior-posterior, superior-inferior, and medio-lateral displacements in the cerebellar tonsils and medulla (∼16%-∼73%) of the CM-I group. The ratio of neural tissue in the foramen magnum was correlated with the superior-inferior tonsillar motion (r=0.58). The tonsillar herniation was correlated with the anterior-posterior motion of the tonsils (r=0.61), and the anterior-posterior and medio-lateral motions of the medulla (r=0.66, and r=0.57). The medio-lateral motion of the tonsils was the only indicator of surgical outcomes (p=0.03, and AUC=0.95), with improved outcomes in subjects with larger motion.