Atlantal facet geometry in Chiari I malformation.

Introduction: Chiari I malformation (CMI) is a complex condition characterized by cerebellar herniation through the foramen magnum and is frequently coincident with other craniovertebral junction abnormalities. Symptoms are varied, and the complete disease etiology is poorly understood. The primary aim of our study is to assess atlantal facet geometry in CMI patients to further elucidate disease pathogenesis. Materials and Methods: Forty-six CMI-affected female patients (29.48 years ± 8.35) (Chiari1000 database) and 55 female controls (32.11 years ± 4.81) (New Mexico Decedent Image Database [NMDID]) were included. Twenty 3D landmarks were placed around the perimeter of each facet by a blinded landmarker. Coordinates were subjected to a generalized Procrustes superimposition. A between-groups principal component analysis (bgPCA) was used to explore differences between groups. The protocol was completed by a second landmarker to validate results. Results: The bgPCA scores were significantly different between CMI patients and controls ( Conclusions: The geometric analysis suggests distinct facet differences in CMI facet shape. CMI etiology is complex, and wholistic anatomical assessment using geometric or multiplanar methods may identify new clinical targets or provide a fresh approach to morphologically driven pathogenesis.