Left arteriae vertebralis canal in atlas – Kimmerle anomaly

Atlas, the ring form of vertebra bears sulcus over posterior arch for third part of vertebral artery. We report a case of presence of osseous bridge on the left side of human atlas, connecting posterior part of superior articular process to the posterior arch of atlas. Sulcus vertebrae for third part of vertebral artery over superior aspect of posterior arch of atlas, converted into foramen. Also considered as ponticulus posterior of the atlas, an anatomic variant – is a retrogressive and morphological phenomenon considered as Kimmerle anomaly. Complete ossification of ligamentous free margin of posterior atlanto-occipital membrane can lead to complete arcuate foramen. Knowledge of this variant prevents complication during lateral mass screw fixation, posterior laminectomy, endovascular surgery.