Craniospinal space reduction and malalignment due to atlas assimilation in Basilar Invagination-A case-control study.

Introduction: Type I Basilar invagination is associated with the assimilation of the anterior arch of the atlas. Observation suggests that the assimilation of the atlas does not allow the development of the normal space between the skull and C1 and displaces the high cervical spine towards the neural structures, posteriorly positioned. Purpose: The objective of this work is to evaluate craniospinal alignment in patients with type I Basilar invagination and AOA in comparison with normal subjects (Type I).