• Spine · May 2009

    Transverse foramen of the atlas (C1) anteriorly unclosed: a misknown human variant and its evolutionary significance.

    • Franck Billmann and Jean-Marie Le Minor.
    • Institute of Normal Anatomy, ULP, Strasbourg, France.
    • Spine. 2009 May 20; 34 (12): E422-6.

    Study DesignMorphologic study of 500 human adult atlases, 256 atlases of nonhuman adult primates representing 37 genera, and 25 human atlases of newborns and young individuals from birth to 3 years of age.ObjectiveTo provide original observations to attempt to understand the anterior unclosure of the transverse foramen of the human atlas, to ascertain its occurrence in primates, and to offer some elements regarding the evolutionary and functional significance of this disposition.Summary Of Background DataAnteriorly unclosed transverse foramen is one of the classic variants of the human atlas, however, rare quantitative data are available in the literature and this disposition remains little understood.MethodsMacroscopical study (dried bones).ResultsIn humans, an anteriorly unclosed transverse foramen was observed on one or both sides in 51 individuals of the 500 in the present series (10.2%); bilateral occurrence (symmetric manifestation) was observed in 45.1% of the anterior unclosures and unilateral occurrence in 54.9%; no significant right or left predominance was observed in the frequency of lateral occurrence. In human newborns and young individuals (from birth to 3 years of age), the transverse foramen was anteriorly unclosed in all of the 25 cases studied. In nonhuman primates, some bilateral or unilateral cases of anterior unclosure were only observed in hominoids, except gibbons: orangutans (8.3%), gorillas (10.5%), and chimpanzees (14.3%).ConclusionThe anteriorly unclosed transverse foramen of the atlas seems to be the result of an evolutionary tendency characteristic of hominoids within primates and could be interpreted as a shared derived character (i.e., synapomorphy) and as the persistence in adults of a juvenile pattern (i.e., paedomorphosis). It must not be interpreted as a pathologic erosion or destruction but as being a simple normal variant.

      Pubmed     Full text   Copy Citation     Plaintext  

      Add institutional full text...

    Notes

     
    Knowledge, pearl, summary or comment to share?
    300 characters remaining
    help        
    You can also include formatting, links, images and footnotes in your notes
    • Simple formatting can be added to notes, such as *italics*, _underline_ or **bold**.
    • Superscript can be denoted by <sup>text</sup> and subscript <sub>text</sub>.
    • Numbered or bulleted lists can be created using either numbered lines 1. 2. 3., hyphens - or asterisks *.
    • Links can be included with: [my link to pubmed](http://pubmed.com)
    • Images can be included with: ![alt text](https://bestmedicaljournal.com/study_graph.jpg "Image Title Text")
    • For footnotes use [^1](This is a footnote.) inline.
    • Or use an inline reference [^1] to refer to a longer footnote elseweher in the document [^1]: This is a long footnote..

    hide…