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Arcuate foramen: "Anatomical variation shape or adaptation legacy?"
Giulia Cossu1,2, Louis-Marie Terrier1, Christophe Destrieux1
1Department of Neurosurgery, Bretonneau University Hospital, Tonnellé Boulevard 2, Tours, France.
Surgical and Radiologic Anatomy : SRA
|January 19, 2019
Summary
The rare arcuate foramen, an anatomical variant in humans, was consistently found in mammoths. This suggests the arcuate foramen may be an evolutionary disadvantage, potentially contributing to mammoth extinction.
Area of Science:
- Paleoanatomy
- Evolutionary Biology
- Human Anatomy
Background:
- The arcuate foramen is a rare anatomical variant where the vertebral artery groove on the atlas becomes an osseous canal.
- This variant is occasionally linked to neurological and pain symptoms, including vertigo and vertebro-basilar insufficiency.
Purpose of the Study:
- To investigate the evolutionary significance of the arcuate foramen.
- To determine if the arcuate foramen is a mere anatomical variation or an ancestral adaptation.
Main Methods:
- Comparative anatomical analysis of five mammoth (Mammuthus primigenius) atlas specimens.
- Comparison of mammoth atlas with five African elephant (Loxodonta africana) atlas specimens.
Main Results:
- All examined mammoth atlas specimens exhibited a complete arcuate foramen.
- The vertebral artery traversed this foramen before becoming intradural in mammoths.
- African elephant atlas specimens displayed only a groove, lacking the arcuate foramen.
Conclusions:
- The consistent presence of the arcuate foramen in mammoths suggests it may not be a random variation.
- This anatomical feature might have posed an evolutionary disadvantage, potentially contributing to the extinction of mammoths.
- The low prevalence of the arcuate foramen in humans may result from natural selection favoring individuals without this variant.