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Atlantal facet geometry in Chiari I malformation
Jonathan Asbury Millard1, Ishan Ransika Perera1, Brooke Scardina1
1Department of Biomedical Sciences, Edward Via College of Osteopathic Medicine, Blacksburg, VA, USA.
Insights
Chiari I malformation (CMI) is linked to distinct atlantal facet geometry, with CMI patients exhibiting smaller, more horizontal facets. This geometric analysis offers insights into CMI pathogenesis and potential new clinical targets.
Area of Science:
- Neurosurgery
- Anatomy
- Biomechanical Engineering
Background:
- Chiari I malformation (CMI) is a complex condition involving cerebellar herniation, often associated with craniovertebral junction abnormalities.
- The precise etiology of CMI remains poorly understood, necessitating further investigation into its underlying anatomical factors.
Purpose of the Study:
- To investigate and characterize the geometric differences in atlantal facet shape between individuals with Chiari I malformation and healthy controls.
- To explore the potential role of atlantal facet morphology in the pathogenesis of Chiari I malformation.
Main Methods:
- A comparative geometric analysis was performed on 46 female CMI patients and 55 female controls using 3D landmark data.
- Generalized Procrustes superimposition and between-groups principal component analysis (bgPCA) were employed to analyze facet shape variations.
- Inter-observer reliability was assessed through a second blinded landmarker's validation.
Main Results:
- Significant geometric differences were observed in atlantal facet shape between CMI patients and controls (P = 0.00022).
- CMI patients displayed smaller, more horizontally oriented facets, particularly evident in the blunted anterior aspect.
- These findings were validated by a second independent analysis.
Conclusions:
- The study identifies distinct atlantal facet geometric variations associated with Chiari I malformation.
- Geometric and multiplanar anatomical assessments may reveal novel clinical targets and advance the understanding of CMI pathogenesis.
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 (W = 689, P = 0.00022). Chiari malformation patients tended to have more negative overall scores, which coincided with smaller, more horizontally oriented facets. These differences were driven largely by the anterior aspect of the facets, which in CMI patients were notably blunted, lacking the typical medial angulation that contributes to the facet's usually reniform shape. The error study conducted by the second blinded landmarker yielded similar differences between CMI and control groups (W = 704, P = 0.00104).
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.
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