Proximal adjacent segment disease manifesting as retro-odontoid pseudotumour following fusion to C2.

BACKGROUND: Although adjacent segment disease (ASD) following anterior cervical fusion has been well described in the literature, there is relative paucity of data on this pathology after posterior cervical fusion. To our knowledge, there have been no reported cases of proximal ASD following posterior fusion to C2. CASE DESCRIPTION: We present 2 cases of proximal ASD presenting as retroodontoid pseudotumors following posterior fusion to C2, both in middle-aged females without history of rheumatologic disease. The first occurred in a patient with Klippel-Feil deformity 13 years after C2-6 posterior cervical fusion, the second in a patient 3 and a half years following revisional circumferential C2-T2 fusion. Both were successfully treated with proximal extension of laminectomy and fusion to the occiput, supplemented in the first patient by transdural decompression of retroodontoid mass. CONCLUSIONS: Proximal ASD can manifest as retroodontoid pseudotumor at variable time intervals following posterior fusion to C2. Clinicians must account for this possibility in their decision making.