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Yoji Komatsu, Tomoyuki Shibata, Susumu Yasuda, Yukio Ono, and Tadao Nose

T he craniovertebral junction is one of the most common sites of malformations. 3, 5, 7 One such malformation, hypoplasia of the atlas, was first described by Wackenheim 8 in 1974. Atlas hypoplasia rarely causes myelopathy; the neurological and neuroradiological findings and treatment have been reported for only one patient with this condition. 4 This paper describes a severe case of high cervical myelopathy caused by atlas hypoplasia. Case Report This 56-year-old man was admitted to Kensei General Hospital after he hit his forehead during a fall. The

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Curtis A. Dickman, Mark N. Hadley, Carol Browner, and Volker K. H. Sonntag

T he first large series of fractures of the atlas was compiled by Sir Geoffrey Jefferson in 1920. 6 He reported four cases of atlas fractures and described 42 others collected from the world literature. Twenty-five of these 46 cases were defined as “complicated atlas fractures,” 19 of which were combination C1–2 fracture injuries. Since Jefferson's initial review, little has been written about combination fractures that involve both the atlas and the axis. Their relative incidence is unknown, and guidelines directing their management have not been defined

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Daniel May, Benoît Jenny, and Antonio Faundez

P rogressive cervical myelopathy is most frequently associated with spinal degenerative changes responsible for mechanical compression and vascular compromise. The anatomical basis usually is a combination of spondylosis, disc herniation, and spinal instability. 1, 9 This disease, however, generally occurs below C-3 and only rarely above C-2. 2, 6 Nontraumatic C-1 compression is usually related to congenital anomalies. These anomalies often involve the posterior arch of C-1 and the defects range from partial to total agenesis. 17 Hypoplasia of the atlas

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Paul J. Apostolides, Nicholas Theodore, Dean G. Karahalios, and Volker K. H. Sonntag

A t our institution, acute combination atlas—axis fractures have been seen in the following types of injuries: 3% of all acute cervical spine, 12% of all acute upper cervical spine, 42% of all acute atlas, and 14.5% of all acute axis fractures. 9, 11 These combinations have been associated with a higher rate of neurological morbidity than isolated C-1 or C-2 fractures and have required surgical stabilization more often than other breaks. 9, 11 Nevertheless, approximately three-fourths of all patients with acute combination atlas—axis fractures can be treated

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Vincent Y. Wang, Vedat Deviren, and Christopher P. Ames

A neurysmal bone cysts are rare benign tumors with a prevalence of 0.14 cases per 100,000 people. 11 A majority of cases arise in adolescence, and there is a female predominance. 2 , 11 This lesion accounts for 1.4% of all primary bone tumors. 16 Aneurysmal bone cysts occur mainly in the long bones, with spinal involvement in 10–30% of cases. 2 , 15 , 16 Cervical spine ABCs account for about one-third of spinal ABCs, and atlas involvement occurs in 1% of cases. 1 , 7 , 14 Resection of ABCs in the atlas is difficult because of the location and the lack

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Mehmet Senoglu, Sam Safavi-Abbasi, Nicholas Theodore, Nicholas C. Bambakidis, Neil R. Crawford, and Volker K. H. Sonntag

–71 years) were dissected at the level of C-1, and congenital defects of the posterior and anterior arch of the atlas were recorded. Altogether, 1354 cases were evaluated. Defects were grouped according to the aforementioned classification of Currarino et al. 2 Results Overall, in the 1354 evaluated cases (1104 patients, 166 dried specimens, and 84 fresh cadaveric specimens), 40 anomalies (2.95%) were found. On cervical spine CT scans obtained in 1104 patients, congenital defects of the C-1 posterior arch were observed in 37 (3.35%) ( Table 1 ). Of these 37 patients

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Joseph H. Piatt Jr. and Leslie E. Grissom

S tudy has been devoted to the normal development of the atlas and the axis in childhood as imaged by skeletal radiography and CT scanning. 4 , 5 , 7 , 9 , 14–16 , 20 , 22 Early investigations were purely descriptive. 4 , 9 Some papers have focused on the evolution of single anatomical features over time. 7 More recent work has attempted to be quantitative, but the datasets have been small in relation to the frequencies of common variations. 5 , 14–16 , 22 Motivated by an interest in more confident distinction among synchondroses, developmental

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Satoshi Yamaguchi, Kuniki Eguchi, Yoshihiro Kiura, Masaaki Takeda, and Kaoru Kurisu

foramen of C-1. Subsequently, the VA courses posteromedially in a horizontal groove on the upper surface of the posterior arch of the atlas. Finally, the VA abruptly turns in the anterior direction to penetrate the dural tube between the foramen magnum and the atlas. 16 In most articles, schematic drawings of the VA over the posterior arch of the atlas show the VA running closely to the superior articular facet of C-1 and the VA groove on the posterior arch of the atlas. However, in actual clinical imaging, the course of most VAs is somewhat different—after exiting the

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Martijn Torreman, Ivo T. H. J. Verhagen, Menno Sluzewski, Alexander J. M. Kok, and Willem Jan van Rooij

T otal agenesis and different forms of partial agenesis of the posterior arch of the atlas (C-1) are rare anomalies. 14 Sometimes they are associated with other congenital anomalies of the bony cervicocranial region and/or spine. Isolated partial agenesis of the posterior arch of the atlas was initially considered a benign variation without any clinical or pathological significance. 4 There is, however, increasing evidence that neurological symptoms may occur after minor cervical trauma in patients with an isolated partial agenesis of the posterior arch of

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R. Shane Tubbs, E. George Salter, and W. Jerry Oakes

O ccipitalization of the atlas (also known as atlantooccipital assimilation) is thought to be one manifestation of the so-called occipital vertebrae (that is, incomplete segmentation between the atlantal and occipital bones). 2 There is, however, little information in the literature regarding the course of the VA in these cases. In his work on variations of the foramen magnum, Harrower 2 briefly stated that in one specimen in which the right lateral mass of the atlas was fused to the occiput, the sulcus for the VA was converted into a canal. In the