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

Background contextIn cranio-vertebral junction, retro-odontoid pseudotumor without evidence of rheumatoid arthritis is a rare condition.PurposeTo discuss the mechanism of enlarging retro-odontoid pseudotumor after expanding cervical laminoplasty as a predictable complication.Study designWe report a rare case of an elderly man with non-inflammatory retro-odontoid pseudotumor after cervical expanding laminoplasty.Patient sampleA 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 measuresPre- and postoperative image, including X-ray and MRI, and the Japanese Orthopaedic Association scores for cervical myelopathy were assessed.MethodsThe 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.ResultsOne 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.ConclusionsThe 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.