Figure 3: (a) Pre-operative sagittal T2-weighted magnetic resonance image demonstrating intramedullary high signal-intensity changes at the posterior arc of the atlas. High signal-intensity changes between the cranial unit and the body of the axis without spinal cord compression (arrow) suggest the presence of instability at the level (b) Post-operative sagittal T2-weighted magnetic resonance image showing that the intramedullary high signal-intensity changes at the posterior arc of the atlas had disappeared (arrowhead)