Figure 4: Intraoperative photos. (a) on the ventral surface of the DM, after retraction of the spinal cord, an ossified formation (blue outline) perforating the DM is visualized; (b) final stage of removal of the formation, the defect of the dura mater is better visualized (green contour); (c) fully visualized linear defect of the dura mater; (d) the defect of the dura mater is sutured. DM: Dura mater