“Split atlas” in a trauma and nontrauma patient: two different case reports for a rare congenital malformation

Abstract

Congenital atlas abnormalities are rare and often asymptomatic findings, accidentally detected in trauma and, more rarely, in nontrauma patients. Rachischisis in both anterior and posterior atlas arches, condition defined as ‘‘split atlas,” is extremely uncommon and it may well be confused with fracture. Being able to discriminate between these 2 conditions is an essential step in patient care management. In this article, we report 2 cases of split atlas ascertained in both trauma and nontrauma patients. The first concerning a 54-year-old man fell from a 2 m scaffold, and the second related to a 25-year-old woman suffering from treatment-resistant headaches. Subsequently we proceed to analyse the embryology of these abnormalities, and later to discuss pitfalls, tips and tricks useful to a correct diagnosis, in order to achieve an accurate management of split atlas. Specifically, we outline the crucial radiological features to identify, that are beneficial to an efficient differential diagnosis between congenital atlas abnormalities and fracture. These include smooth corticated margins of the cleft, and <3 mm lateral displacement of C1 lateral masses.

Imaging of Developmental Malformations Affecting Craniocervical Junction

“…MRI is superior to CT in achondroplasia patients for the evaluation of the craniocervical junction. It provides imaging of the brainstem and cervical cord, including cord compression and T2 signal changes, as well as visualization of the posterior fossa structures [13] . In our study two patients were included with achondroplasia both of them underwent MRI, which showed cervico-medullary kinking & spinal cord compression.…”

The Great Mimickers of Spinal Pathology

“…Rarely, the atlas is also not fused in the anterior location that results in a so-called split atlas. 1…”

“…Rarely, the atlas is also not fused in the anterior location that results in a so-called split atlas. 1 An inferior accessory ossicle of the anterior arch of the atlas (►Fig. 1), a triangular shaped ossicle with a peripheral layer of mature cortical bone, is an asymptomatic normal variant, and its prevalence and clinical significance may be underestimated.…”

Reporte de Caso de Traumatismo Raquimedular con Hallazgo Incidental de Rara Malformación de Columna Cervical: Atlas Bipartita

“…Las mujeres tienen una mayor prevalencia que los hombres. La raquisquisis en los arcos anterior y posterior del atlas, condición definida como "atlas dividido", es extremadamente infrecuente y bien puede llegar a confundirse con una fractura 1 . Un atlas dividido o bipartito es una anomalía congénita que resulta en una esquisis anterior y posterior coexistente debido al fracaso de la fusión de los arcos tanto anterior y posterior.…”