Persistent proatlas with additional segmentation of the craniovertebral junction - The Tsuang-Goehmann-Malformation

Abstract

Case study description and analysis of a complex craniovertebral dysplasia in an 8-year-old male patient, in which conventional cervical spine radiographs demonstrated a regularly differentiated occipital base, as well as the presence of two lateral masses of the proatlas vertebra and two lateral masses of the atlas vertebra. Further assessment included computed tomography of the occipital base and the upper cervical spine as well as three-dimensional reconstruction. Malsegmentation of the fourth occipital vertebra can result in various anomalies that are known as 'manifestation of the proatlas'. The occurrence of a persistent proatlas with additional segmentation of the craniovertebral junction represents an extremely rare dysplasia. To our knowledge, it is the second report concerning the persistence of a complete human proatlas vertebra. We consider the biomechanical and embryological particularities of this complex dysplasia to represent sufficient basis for future differentiation from other malformations of the fourth occipital vertebra. Comprehensive literature review and discussion about the entity will be provided.

Keywords: CT scan; Sandberg-Gutmann; X-ray; additional segmentation; atlas vertebra; cervical spine; computed tomography; craniovertebral junction; malformation; manifestation of occipital vertebra; manifestation of proatlas; occipital vertebra; persistent proatlas; plain radiographs.

Figure 1

Eight-year-old boy with persistent proatlas and additional segmentation of the craniovertebral junction. Technique: Plain a.p. radiograph according to Sandberg-Gutmann (75 kvp, 10 mAs). Findings: Additional lateral masses of C1 (black asterisks upper row) representing a complete persistence of proatlas vertebra and the “regular” lateral masses of C1 (black asterisks lower row).

Figure 2

Eight-year-old boy with persistent proatlas and additional segmentation of the craniovertebral junction. Eight upper cervical spine segments. Technique: Lateral plain radiograph according to Sandberg-Gutmann (75 kvp, 10 mAs). Findings: Two posterior arches of C1 (white arrows) as well as normal C2 vertebra (white asterisk). The anterior arches of “regular” C1 and of the persisting proatlas vertebra are missing.

Figure 3

Eight-year-old boy with persistent proatlas and additional segmentation of the craniovertebral junction. Eight upper cervical spine segments. Technique: Lateral plain radiograph in inclination according to Sandberg-Gutmann (75 kvp, 10 mAs). Findings: Two posterior arches of C1 (white arrows). No obvious functional instability.

Figure 4

Eight-year-old boy with persistent proatlas and additional segmentation of the craniovertebral junction. Technique: Lateral plain radiograph in reclination according to Sandberg-Gutmann (75 kvp, 10 mAs). Findings: Two posterior arches of C1 (white arrows) as well as normal C2 vertebra (white asterisk). No functional instability in reclination.

Figure 5

Eight-year-old boy with persistent proatlas and additional segmentation of the craniovertebral junction. Technique: Non contrast CT (Siemens, 110kV, 25mAs, 0,6 mm, 16,06 mGycm), coronal plane. Findings: Lateral masses of ‘two atlas-like vertebrae’ (white arrows) - the proatlas vertebra (above) and the atlas vertebra (below) - as well as os odontoideum (white asterisk).

Figure 6

Eight-year-old boy with persistent proatlas and additional segmentation of the craniovertebral junction. Technique: Non contrast CT (Siemens, 110kV, 25mAs, 0,6 mm, 16,06 mGycm), sagittal plane. Findings: Occipital base and the lateral masses of ‘two atlas-like vertebrae’ (white arrows). Proatlas vertebra (above) and “regular” atlas vertebra (below).

Figure 7

Eight-year-old boy with persistent proatlas and additional segmentation of the craniovertebral junction. Technique: Non contrast CT (Siemens, 110kV, 25mAs, 0,6 mm, 16,06 mGycm), sagittal plane. Findings: Os odontoideum at the top of dens axis (white arrow) with characteristic location. Clivus without malformation.

Figure 8

Eight-year-old boy with persistent proatlas and additional segmentation of the craniovertebral junction. Technique: Non contrast CT (Siemens, 110kV, 25mAs, 0,6 mm, 16,06 mGycm). 3-D-reconstruction. Findings: Anterior aspect with dens axis and the lateral masses of ‘two atlas-like vertebrae’ (white asterisks). Anterior arches of proatlas (above) and atlas vertebra (below) are missing. Os odontoideum at the top of dens axis with characteristic location. Dens axis without any sign of malformation.

Figure 9

Eight-year-old boy with persistent proatlas and additional segmentation of the craniovertebral junction. Technique: Non contrast CT (Siemens, 110kV, 25mAs, 0,6 mm, 16,06 mGycm). 3-D-reconstruction. Findings: Posterior aspect with posterior arch of C2, proatlas (white asterisks upper row) and atlas vertebra (white asterisks lower row). Malfusion of posterior arch of the persisting proatlas whereas the posterior arch of the “regular” C1 is closed.

Figure 10

Eight-year-old boy with persistent proatlas and additional segmentation of the craniovertebral junction. Technique: Non contrast CT (Siemens, 110kV, 25mAs, 0,6 mm, 16,06 mGycm). 3-D-reconstruction. Findings: Left lateral aspect showing the lateral masses of the proatlas (white asterisk above) and atlas vertebra (white asterisk below) representing an additional segment of the upper cervical spine.

Figure 11

Eight-year-old boy with persistent proatlas and additional segmentation of the craniovertebral junction. Technique: Non contrast CT (Siemens, 110kV, 25mAs, 0,6 mm, 16,06 mGycm). 3-D-reconstruction. Findings: Right lateral/anterior aspect showing the lateral masses of proatlas (above) and atlas vertebra (below) - (white asterisks). Malfusion of the anterior arches of proatlas (above) and atlas vertebra (below).