A case of fourth atlanto-axial facet joint: anatomical description.
To report a rare fourth atlanto-axial joint.



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.



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.



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.
Department of Neurosurgery, Xuanwu Hospital, Capital Medical University, 45 Changchun St, Beijing, 100053, People's Republic of China.|Department of Neurosurgery, Beijing Hospital, Beijing, 100730, People's Republic of China.
Xing-Wen
XW
Wang
Department of Neurosurgery, Xuanwu Hospital, Capital Medical University, 45 Changchun St, Beijing, 100053, People's Republic of China.
Feng-Zeng
FZ
Jian
Department of Neurosurgery, Xuanwu Hospital, Capital Medical University, 45 Changchun St, Beijing, 100053, People's Republic of China. fengl15210027143@yeah.net.
Feng
F
Ling
D001268:Atlanto-Axial Joint / Q000002:abnormalities* / Q000033:anatomy & histology; D002102:Cadaver; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D014057:Tomography, X-Ray Computed; D055815:Young Adult
Anomaly; Atlantoaxial; Facet joint