Anatomic and Radiologic Appearance of Several Variants of the Craniocervical Junction

University Hospital RWTH Aachen, Aachen, North Rhine-Westphalia, Germany
Skull Base 02/1996; 6(2):83-94. DOI: 10.1055/s-2008-1058649
Source: PubMed


Four typical manifestations of the occipital vertebra are described from both an anatomic and a radiologic point of view; the basilar process, the condylus tertius, the paracondylar process, and the isolated prebasioccipital arch. The clinical importance of the described variants is discussed.

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    • "The third atlanto-occipital joint, if present, may disrupt the biomechanics between the occiput and the atlas resulting in mechanical pain and increased rigidity. The condition may also be associated with an osseous torticolis [28]. The head may adopt an attitude of flexion termed caput obstipum [29]. "
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    ABSTRACT: Minor variations in the ossicles, foramina and ridges of the cranium have aroused the curiosity of anatomists for many decades. These non-metric variants help us to study the genetic relationships among ancient populations. Since these traits show considerable frequency differences in different populations, they can be used as anthropological characters in epidemiological studies. These variants indirectly reflect the part of underlying genotype of a given population thus implying their usefulness in biological comparisons of related groups. They can be used for the assessment of the existence of the parental structures within a community or as taxonomic indicators. For anthropological studies, the traits should be genetically determined, vary in frequency between different populations and should not show age, sex, and side dependency. The present study was conducted on hundred dry adult human skulls from Northern India. They were sexed and studied for the presence of hyperostotic traits (double hypoglossal canal, jugular foramen bridging, and paracondylar process). Sexual and side dimorphism was observed. None of the traits had shown statistically significant side and sexual dimorphism. Since the dimorphism is exhibited by none of them, it can be postulated that these traits are predominantly under genetic control and can be effectively used for population studies.
    Anatomy & cell biology 12/2012; 45(4):268-73. DOI:10.5115/acb.2012.45.4.268
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    • "Basilar processes, also called mammilar or papillar or precondylar processes, are considered a relatively unusual observation occurring in approximately 3– 4% of the examined skulls (Berry & Berry, 1967; Berry, 1975; Prescher et al., 1996; Keskil et al., 2003). They are commonly described as variably shaped bone formations positioned anteromedially to the occipital condyles. "
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    ABSTRACT: The craniovertebral junction (CVJ) is a transitional region of the spine that exhibits extensive structural variability. Developmental defects include a vast array of anatomical anomalies that result from remnants of the proatlas and are grouped under the term 'occipital vertebra'. The purpose of the present paper is to describe the case of a medieval skeleton, which was found to display a previously unreported manifestation of occipital vertebra. It consisted of two large basilar processes that articulated with the anterior arch of the atlas. In addition, the left process exhibited a supplementary contact zone with the dens of the axis. These structural defects were associated with an accessory canal situated posterior to the right hypoglossal canal.
    Anatomical Science International 01/2009; 83(4):286-90. DOI:10.1111/j.1447-073X.2007.00213.x · 0.83 Impact Factor
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    ABSTRACT: A 21-year-old female presented to a chiropractic clinic with chronic neck and headache pain. She had an osseous torticollis and abnormal range of neck motion on rotation to the left. Radiographic examination revealed a unilateral paracondylar process of the occiput fusing to the lateral transverse process of the atlas. A paracondylar process is classified as an occipital vertebra. It is an enlarged bony process of the cranial base which projects caudally towards the transverse process of the atlas. She was treated with spinal manipulation below the level of fusion which resulted in a marked decrease in headache and neck pain. The embryology, frequency, radiographic appearance and clinical implications of a paracondylar process are discussed in this paper.
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