Compression Myelopathy due to Proliferative Changes around C2 Pars Defects without Instability

We report a case with compression myelopathy due to proliferative changes around the C2 pars defects without instability. A 69-year-old man presented with progressive clumsy hands and spastic gait. Plain radiographs showed bilateral spondylolysis (pars defects) at C2 and fusion between C2 and C3 spinous processes. Dynamic views revealed mobility through the pars defects, but there was no apparent instability. Computed tomography showed proliferative changes at the pars defects, which protruded into spinal canal. On magnetic resonance imaging, the spinal cord was compressed and intramedullary high signal change was found. A diagnosis of compression myelopathy due to proliferative changes around the C2 pars defects was made. We performed posterior decompression. Postoperatively, symptoms have been alleviated and images revealed sufficient decompression and no apparent instability. In patients with the cervical spondylolysis, myelopathy caused by instability or slippage have been periodically reported. The present case involving C2 spondylolysis is extremely rare.