Abstract

Background: Atlas, first cervical vertebra bears sulcus over posterior arch for third part of vertebral artery. Sometimes an osseous bridge converts the sulcus into a foramen called as Arcuate foramen. It is commonly called as Kimmerle’s anomaly, also known as Ponticulus Posticus. It is the product of the complete or incomplete ossification of the posterior atlanto-occipital membrane over the vertebral artery groove resulting in the formation of a foramen (Arcuate foramen) containing the vertebral artery and the posterior branch of the C-1 spinal nerve. This variation has been associated with vertebro-basilar insufficiency symptoms, various types of headaches, and acute hearing loss. The knowledge of this variant prevents complications during lateral mass screw fixation, posterior laminectomy and endovascular surgery. Aims: The aim of the present study was to analyze the percentage of incidence of arcuate foramen and to identify its clinical significance. Materials and Methods: Hundred dried human atlas bones were used to study the presence of arcuate foramen in the department of Anatomy at ESIC Medical College and PGIMSR, Rajajinagar, Bangalore. Results: We came across the presence of arcuate foramen in two out of hundred bones. In both the atlas bones, osseous bridge extending from posterior aspect of superior articular facet to the posterior arch of atlas on the left side, forming arcuate foramen, posterior to foramen transversarium was observed. Conclusion: Arcuate foramen commonly called as Kimmerle’s anomaly where in a groove for vertebral artery is converted into a foramen by ossification of the ligament. Awareness of osseous bridging is essential in performing cranio-cervical junction surgeries. It also serves as an anthropological data and also identifying the impact of complete arcuate foramen on the signs and symptoms of vertebra-basilar insufficiency.

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