Enlarging retro-odontoid pseudotumor after expanding cervical laminoplasty in the presence of kyphosis.

Background Context: In cranio-vertebral junction, retro-odontoid pseudotumor without evidence of rheumatoid arthritis is a rare condition.

Purpose: To discuss the mechanism of enlarging retro-odontoid pseudotumor after expanding cervical laminoplasty as a predictable complication.

Study Design: We report a rare case of an elderly man with non-inflammatory retro-odontoid pseudotumor after cervical expanding laminoplasty.

Patient Sample: A 76-year-old man presented with progressive quadriparesis of two week's duration caused by enlarging retro-odontoid soft tissue mass after cervical laminoplasty.

Outcome Measures: Pre- and postoperative image, including X-ray and MRI, and the Japanese Orthopaedic Association scores for cervical myelopathy were assessed.

Methods: The patient subsequently underwent resection of the posterior arch of the atlas and posterior fusion from the occiput to C6 using Olerud system without removal of the retro-odontoid soft tissue mass.

Results: One year after surgery, the Japanese Orthopaedic Association scores for cervical myelopathy improved from 1 to 10 points, and postoperative MRI showed a mild reduction in the size of the retro-odontoid soft tissue mass.

Conclusions: The kyphotic stability from C3 to C7 after laminoplasty, leading to a compensatory hyperlordosis at the occipitocervical junction, may cause the development of a degenerative osteoarthritic change, resulting in the production of an enlarging mass. Not only posterior compression of spinal cord due to posterior arch of the hyperextended atlas but also anterior compression of spinal cord due to retro-odontoid pseudotumor probably triggered the severe myelopathy. Laminoplasty may be inappropriate in cervical myelopathy with kyphosis.