Anat Cell Biol.  2021 Mar;54(1):128-131. 10.5115/acb.20.264.

Chiari 1.5 malformation, accessory odontoid synchondrosis, and ventral compression: case report

Affiliations
  • 1Department of Neurosurgery, Tulane Center for Clinical Neurosciences, Tulane University School of Medicine, New Orleans, LA, USA
  • 2Department of Neurology, Tulane Center for Clinical Neurosciences, Tulane University School of Medicine, New Orleans, LA, USA
  • 3Department of Structural & Cellular Biology, Tulane University School of Medicine, New Orleans, LA, USA
  • 4Department of Neurosurgery and Ochsner Neuroscience Institute, Ochsner Health System, New Orleans, LA, USA
  • 5Department of Anatomical Sciences, St. George’s University, St. George’s, Grenada, West Indies

Abstract

The pathogenesis of Chiari 1 malformations has been explained in several different ways, but extensive evidence suggests a relationship between loss of volume within the posterior cranial fossa and Chiari 1 presentations. It is important to be able to differentiate Chiari 1.5 from Chiari 1 malformations as they have similar clinical presentations, but the latter have progressed further and are characterized by caudal herniations of the brain stem through the foramen magnum. Despite the similarities of presentation, Chiari 1.5 malformations have greater rates of complications following posterior decompression surgeries, which are typically performed to relieve ventral compression. An improved understanding of the odontoid synchondroses could lead to better understanding of Chiari malformations and lead to improved treatment of patients with these presentations. Here we present a rare case of an accessory odontoid synchondrosis in a patient with a Chiari 1.5 malformation and ventral compression.

Keyword

Dens; Odontoid process; Anatomy; Chiari malformations; Odontoid synchondroses

Figure

  • Fig. 1 Schematic drawing of the ossification centers and synchondroses (arrows) of the C2 vertebra.

  • Fig. 2 Two odontoid synchondroses in the same C2 vertebra (white arrows) shown in a midsagittal magnetic resonance imaging image. The upper white arrow notes the accessory synchondrosis. Note the cerebellar tonsils (asterisk), and the lower part of the brainstem (red star) located below the foramen magnum i.e., Chiari 1.5 malformation. The anterior arch of the atlas (yellow arrow) is not ossified. The posterior arch of C1 and spinous process of C2 are also shown.


Reference

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