Atlantoaxial lateral mass osteoarthritis. A frequently overlooked cause of severe occipitocervical pain.

Localized C1-C2 lateral mass osteoarthritis is a degenerative disorder of the upper cervical spine that has a natural history markedly different from that of degenerative afflictions of the lower cervical spine. Atlantoaxial lateral mass arthritis is a distinct cause of occasionally severe occipitocervical pain in elderly persons. In this series, the diagnosis was suggested by the medical history of nine elderly patients who presented with severe occipitocervical pain (frequently diagnosed as occipital neuralgia). Physical examination demonstrated marked restriction of rotation of the cervical spine to the affected side, and localized tenderness unilaterally at the occipitocervical junction. The diagnosis was confirmed by plain radiographs of the C1-C2 articulation (open-mouth view), demonstrating marked, usually unilateral joint-space narrowing, osteophyte formation, and subchondral sclerosis. Bone scanning demonstrated focal uptake unilaterally at the occipitocervical junction. Additional imaging studies, including computed tomography, magnetic resonance imaging, or cervical myelogram, were performed to rule out coexisting intraspinal pathology. Conservative treatment was usually successful; however, C1-C2 arthrodesis was successful for severe occipitocervical pain due to atlantoaxial lateral mass arthritis not responsive to conservative treatment.