Arcuate foramen

The arcuate foramen (foramen arcuale atlantis, ponticulus posticus or posterior ponticle, or Kimerle anomaly) is a frequently encountered normal variant of the atlas and is easily appreciated on a lateral plain film of the cranio-cervical junction.

It develops by calcification of the posterior atlanto-occipital membrane. The atlantic portion (V3) of the vertebral arteries pass through this foramen.

Incidence is ~8% (range 1-15%) and it is more common in females. It has a variable morphology, can be complete or incomplete and may be unilateral or bilateral.

Radiographic features

Plain radiograph
  • complete or incomplete bony arch is seen over the posterosuperior aspect of the atlas on lateral projections
Spinal anatomy
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Article Information

rID: 16413
Section: Anatomy
Synonyms or Alternate Spellings:
  • Foramen arcuale atlantis
  • Ponticulus posticus
  • Arcuate foramena
  • Posterior ponticle

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Cases and Figures

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    Figure 1: illustration
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    Case 1
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     Case 2
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     Case 3
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    Arcuate foramina
    Case 4
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    Case 5: unilateral
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    Case 6
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    Case 7
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