Anat Cell Biol.  2024 Sep;57(3):468-472. 10.5115/acb.23.281.

Atlantooccipital assimilation associated with combined atlas arch defect: a radiological case report

• Suwannakhan A
• Trerattanavong P
• Yurasakpong L
• Kirisattayakul W
• Kruepunga N
• Tuntiseranee K
• Rumpansuwon K
• Senarai T

• KMID: 2559768
• DOI: http://doi.org/10.5115/acb.23.281

Abstract

In this report, atlantooccipital assimilation (AS), anterior arch defect (AAD), and posterior arch defect (PAD) of the atlas, and several variations around the craniocervical junction were identified on computed tomography (CT) of a patient of unknown sex and age. Coronal and sagittal CT scans showed AS and bilateral fusion of the atlas and the base of occipital bone. Axial CT scan at the atlas revealed PAD type B on the left side and midline AAD. Morphometric measurements indicated a potential ventral spinal cord compression. In addition, mid-sagittal CT revealed the presence of fossa navicularis magna and incomplete formation of the transverse foramen on the right side. This study reports an extremely rare AS associated with AAD, PAD, and other variations of the clivus and the atlas. To our knowledge, no similar case has been reported in the literature.

Keyword

Cervical vertebrae; Cervical atlas; Skull base; Klippel-Feil syndrome; Anatomic variation

Figure

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  Fig. 1 Sagittal (A), coronal (B), axial (C, D) computed tomography scans showing the presence of atlas assimilation (red arrowheads), anterior atlas arch defect (green arrowhead) and posterior arch defect (blue arrowhead). Sagittal image (E) shows the distance between the odontoid apex and Chamberlain’s line, lining between the hard palate and the opisthion (7.5 mm), suggesting basilar invagination into the posterior cranial cavity of skull. The angle between clivus and posterior aspect of odontoid process was 138.8°, indicating predisposition to anterior spinal cord compression.

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  Fig. 2 Three-dimensional reconstruction from the posterior (A) and anterior (B) views of the craniocervical junction showing posterior arch defect (blue arrowhead), fossa navicularis magna (yellow arrowhead), incomplete transverse foramen (red line) and anterior arch defect (green arrow).

Reference

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