Accessory joints between basiocciput and atlas/axis in the median plane

A case of fourth atlanto-axial facet joint: anatomical description

PURPOSE

To report a rare fourth atlanto-axial joint.

METHODS

A cadaveric specimen of a young male adult from occiput to C4 was dissected for anatomical study of craniocervical region. A true fourth atlanto-axial joint was confirmed. Its morphological characteristics were described.

RESULTS

The fourth atlantoaxial joint is rarely seen. The possible embryogenesis is discussed. This case raises an anatomical possibility of a new variant in this region.

CONCLUSIONS

A unique case with an anatomically proven fourth atlantoaxial joint is reported. This anomaly can lead to misdiagnosis. CT scan coupled with MRI can facilitate accurate diagnosis.

Epibulbar osseous choristoma in 8 patients

PURPOSE

To describe the clinical features and histopathology of epibulbar osseous choristoma in a series of patients.

METHODS

Noncomparative case series with chart review of 8 patients.

RESULTS

At presentation, the mean age of the patients was 19 years (median, 19 years; range, 0.8-38 years), with 6 women and 2 men (6 Caucasian, 1 Hispanic, and 1 African American). There were no related systemic syndromes, and visual acuity was unaffected in all cases. The choristoma was superotemporal (n = 8, 100%), with epicenter located in the fornix (n = 8, 100%), deep to Tenon fascia (n = 8, 100%), and of yellow (n = 2, 25%), white (n = 2, 25%), or pink (n = 4, 50%) color. The mean basal dimension was 9 mm (median, 10 mm; range, 3.5-14 mm), and mean thickness was 4 mm (median, 4 mm; range, 2-5 mm). Four cases were managed with observation and 4 with surgical excision, revealing tumor base adherent to the episclera (n = 2, 50%) or loose within Tenon fascia (n = 2, 50%). There were no cases to demonstrate intrascleral involvement, growth, or recurrence.

CONCLUSIONS

Epibulbar osseous choristoma is a congenital lesion of mature bone located superotemporally in the fornix at the level of Tenon fascia or episclera in young patients.

The clivus: anatomy, normal variants and imaging pathology

The clivus is one of the most central parts of the skull base. As diseases of the clivus evade clinical evaluation imaging plays a pivotal role in establishing a diagnosis. This article combines the description of anatomy and pathology with an extensive pictorial essay. Starting with the development and normal macroscopic anatomy of the clivus the reader is then introduced to a large variety of normal variations and developmental disorders some of them with clinical significance. Typical examples of non-neoplastic and neoplastic masses of the clivus and their differential diagnoses are provided. The article concludes with a review of inflammatory disease and trauma.

[Atlantoaxial malformation as a rare cause of dysphagia and snoring]

Abnormalities of the atlantoaxial spine are very rare variants. Bony outgrowths, osteophytes, clefts and aplasia may be misinterpreted as degenerative diseases. One patient presented with intermittent dysphagia and snoring and CT and MRI scans of the cervical spine showed an accessory bone located anterior to the atlas and axis. Atlantoaxial anomalies are often incidental findings without clinical symptoms. Such changes are rarely the cause of intermittent dysphagia and snoring.

Symptomatic occipitocervical paracondylar process

A paracondylar process is a bony exostosis that arises from the skull base lateral to the occipital condyle and extends inferiorly toward the transverse process of the atlas. This congenital anomaly can vary in size from a small protuberance to an elongated process articulating with an epitransverse process arising from C-1. Typically, a paracondylar process is an incidental finding described in anatomical studies. The authors report on a patient with a symptomatic paracondylar process articulating with an epitransverse process that caused occipitocervical pain. Resection of the paracondylar and epitransverse processes completely relieved the patient's pain.

Unusual case of occipital vertebra in a medieval skeleton

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.

The typical appearance of the inferior accessory ossicle of the anterior arch of the atlas

The inferior accessory ossicle of the anterior arch of the atlas is quite rare and has been described in the literature by only few articles. However, these articles have only included plain radiographs in the description. In our case, the above ossicle is illustrated in two imaging modalities, plain radiography and CT imaging. The importance of this ossicle lies in its recognition as only an anatomical variant and not to be confused with other pathological conditions such as a fracture.