1. Characteristics of Ossified Lesions in the Upper Cervical Spine Associated with Ossification of the Posterior Longitudinal Ligament in the Lower Cervical Spine by Yoshiharu Kawaguchi, Shoji Seki, Takeshi Hori, and Tomoatsu Kimura J Bone Joint Surg Am Volume 90(4):748-753 April 1, 2008 ©2008 by The Journal of Bone and Joint Surgery, Inc.

2. Graph illustrating the space available for the spinal cord (SAC) at the C1 level in patients with ossified lesions at the first cervical level (the C1[+]group) and those without such lesions (the C1[−] group). Yoshiharu Kawaguchi et al. J Bone Joint Surg Am 2008;90:748-753 ©2008 by The Journal of Bone and Joint Surgery, Inc.

3. Figs. 2-A, 2-B, and 2-C A fifty-eight-year-old man who had cervical myelopathy due to an ossified lesion of the upper cervical spine behind the dens. Yoshiharu Kawaguchi et al. J Bone Joint Surg Am 2008;90:748-753 ©2008 by The Journal of Bone and Joint Surgery, Inc.

4. Lateral radiograph of the cervical spine, showing that the lesion extends from the continuous type of ossification of the posterior longitudinal ligament caudad to C1. Yoshiharu Kawaguchi et al. J Bone Joint Surg Am 2008;90:748-753 ©2008 by The Journal of Bone and Joint Surgery, Inc.

5. T2-weighted sagittal magnetic resonance image demonstrating spinal cord compression at the C1 level due to the ossified lesion, with a zone of high signal intensity within the spinal cord. Yoshiharu Kawaguchi et al. J Bone Joint Surg Am 2008;90:748-753 ©2008 by The Journal of Bone and Joint Surgery, Inc.