“…Koyama et al first reported a separated lamina of the axis invaginated into the canal in 1986 [ 1 ]. Subsequently, 14 cases of myelopathy caused by invaginated lamina of the axis were reported ( Table 1 ) [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ]. While most anomalies of the axis are in combination with other anomalies (e.g., spina bifida and ossification of the posterior longitudinal ligament), cases of anomalies involving the axis alone are very rare [ 2 , 7 , 10 ].…”