Project information
- Category: Original Research
- Researchers:: Perera, I., Moriarty, S., Simmons, Z., Mahoney, M., Malek, Z., Botkin, C., Millard J.A.
- Awards:: 2023 VCOM-VA Research Day: 1st Place
Accepted for 2023 AANS Scientific Meeting
Abstract
Introduction:
Chiari malformation is typically defined as inferior descent of the cerebellar tonsils
through the foramen magnum. Recent investigations attempting to characterize Chiari I
malformation have included exhaustive collection of linear dimensions and angles in the
midsagittal plane. The primary aim of this study is to describe midbrain and hindbrain
shape using geometric morphometric techniques.
Methods:
Midsagittal MRI images from 94 Chiari-affected females and matched controls were
landmarked using tpsDig264 (v.2.32) and tpsUtil64 (v.1.82). A total of 10 discrete and
155 semilandmarks were placed on features of the midbrain and hindbrain. Generalized
Procrustes superimposition and principal component analysis (PCA) were applied to the
results using MorphoJ (v.1.07a). Independent-samples t-tests were applied to principal
component (PC) scores to evaluate hypotheses related to configurational differences
between groups. Past (v.4.03) and MorphoJ were used to visualize results.
Results:
The PCA revealed 93 loadings with the first four accounting for 65.126% of the overall
variation in the shape. The first PC indicated inferior displacement of the cerebellar
tonsils, posterior displacement of the posterior cerebellar lobe and 4th ventricle with
concomitant ventral migration of the midbrain, and dorsal migration of the medulla. Mean
scores along PC1 were significantly different between affected and control groups (t(93)
= 6.8, p <0.001). In an affected-only analysis, mean shape conformation did not
effectively discriminate between individuals with a history of syringomyelia and
those without. There was a significant difference along PC2 for individuals
receiving a diagnosis under age 30 versus those over age 30 (t(65)=2.4,
p=0.017).
Conclusions:
Geometric analysis effectively discriminates between Chiari-affected
individuals and matched controls. Aside from predictably highlighting tonsillar
ectopia, results demonstrated a number of additional anatomical conformations in
individuals with Chiari I malformation. Future directions should include machine
learning to evaluate subtle shape differences between groups with the goal of
integrating results into clinical decision-making.
References
1. Gaillard F, Yap J, Smith D, et al.: Chiari i malformation.
Radiopaedia.org:2008
2. Hiremath SB, Fitsiori A, Boto J, Torres C, Zakhari N, Dietemann J-L, et al: The
perplexity surrounding Chiari malformations – are we any wiser now? American
Journal of Neuroradiology 41:1975–1981, 2020