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 that the regional brain motion in CM-I was significantly higher than that of the healthy subjects, with anterior-posterior (AP) and superior-inferior (SI) displacements in cerebellar tonsils and medulla having the highest differences between the healthy and CM-I (∼45%–∼73% increased motion in the CM-I group). Interestingly, we found the ratio of neural tissue in the foramen magnum to be directly correlated with the SI tonsillar motion (r=0.58). Tonsillar herniation was directly correlated with the AP motion of the tonsils (r=0.61), and AP and medial-lateral (ML) motions of the medulla (r=0.66, and r=0.57). Subjects with higher tonsillar ML motion prior to surgery showed improved outcome (p=0.03, and AUC=0.95). Although we did not observe a significant correlation between the brains motion and morphometrics on the CM-I symptoms (perhaps due to our small sample size), illustrative cases increase our hope for the development of a future tool based on brain biomechanics.