Abstract
In order to describe the incidence and existing variants of congenital anomalies of the atlas vertebrae in a Caucasian population, we examined 1069 CT scans of the upper cervical spine. We found 41 cases with altered atlas vertebrae, representing 3.8% of all analyzed patients. With 83% of all found anomalies, the predominant type is characterized by a small dorsal cleft (3.2% of all patients). Rare varieties feature unilateral or bilateral dorsal arch defects, combined anterior and posterior clefts (0.2% of all patients) or total erratic atlas vertebra malformation (0.1% of all patients). Atlas arch defects are found nearly 4% at the time. Most anomalies affect the posterior arch, whereas the anterior arch or both are rarely affected. Totally irregular C1 vertebrae are extremely infrequent.
Highlights
Atlas arch anomalies are found mostly coincidentally
We reviewed 255 cervical spine CT scans, 3 cervical and thoracic spine CT
In the 1069 analyzed patients, we found 41 cases of atlas arch defects
Summary
Atlas arch anomalies are found mostly coincidentally. Currarino et al proposed 5 types of atlas posterior arch defects referring to Torklus [2, 5]. Less common are anterior atlas arch defects and the combination of both [3, 4]. Accompanying anomalies include an enlarged anterior arch, cephalad elongation of the spinous process of the axis, and a dense fibrous membrane forming a posterior atlantooccipital membrane [2]. These altered anatomical findings exhibit natural adaption in order to maintain stability and function. Malformations, where C1/C2 junction might be compromised, have to be distinguished from fractures
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