An Osteological Study Of Arcuate Foramen In Atlas And Its Clinical Significance

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 commonlycalled as Kimmerle’s anomaly, also known as Ponticulus Posticus. It is the product of the complete or incompleteossification of the posterior atlanto-occipital membrane over the vertebral artery groove resulting in the formationof 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 identifyits clinical significance.Materials and Methods: Hundred dried human atlas bones were used to study the presence of arcuate foramen inthe 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 theleft 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 isconverted into a foramen by ossification of the ligament. Awareness of osseous bridging is essential in performingcranio-cervical junction surgeries. It also serves as an anthropological data and also identifying the impact ofcomplete arcuate foramen on the signs and symptoms of vertebra-basilar insufficiency.