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.

Proposing novel dorsal Proatlas‐manifestations: Description and classification of three rare phenomena in humans

“…This primordial vertebra is generally referred to as "occipital vertebra" or since Albrecht (1880), as "Proatlas". This Proatlas rarely persists as a complete vertebra between the occipital bone and the atlas, as it has been described by Spittank et al (2016) and Zumbihl et al (2022). A much more typical behavior is the partial persistence, which means the persistence of any substructures of the Proatlas.…”

“…The human craniocervical junction (CCJ) is an anatomically variable region (Christ, 1990; Prescher, 1997), which offers a wide range of morphological peculiarities. Occasionally, new macroanatomical findings and their clinical relevance are brought to light (Sacher et al, 2019; Spittank et al, 2016; Tsuang et al, 2011; Wolf‐Vollenbröker & Prescher, 2021; Zumbihl et al, 2022). However, the interpretation of new findings requires precise knowledge of the previous results, which are manifold and difficult to overview due to the long history of studying the anatomical details of the CCJ by morphological disciplines.…”

Development of the axial skeleton and intervertebral disc

“…Rare diseases that occur in humans called Proatlas Segmentation Anomalies OMIM: 109500 are thought to be caused by failure in the proatlas sclerotome, which will partially go on to form the C1 VB, to undergo resegmentation. These disorders result in dysplasia within the craniovertebral junction and can manifest in various ways clinically, such as cervical VB fusion and ventral brain stem compression (Muthukumar, 2016; Spittank et al, 2016; Umegaki et al, 2017). Klippel-Feil Syndrome (OMIM: 613702), where patients suffer from cervical vertebral fusion due to lack of IVD formation, has also been associated with a disruption in resegmentation and mutations in the GDF6 gene (Tassabehji et al, 2008).…”

IVD Development: Nucleus Pulposus Development and Sclerotome Specification

“…Failure of the proatlas sclerotome, which will partially go on to form the C1 vertebrae, to resegment results in rare disorders observed in humans called Proatlas Segmentation Anomalies (PSA) OMIM: 109500. These disorders result in the malformation of the proatlas and thus dysplasia within the craniovertebral junction [44*, 45*, 46*]. Effects of this disorder can manifest in various ways clinically, such as cervical vertebrae fusion and ventral brain stem compression [46, 44].…”