Figure 2 :Lateral intradural foramen magnum meningioma. (a-c) Preoperative MRI in axial (a), coronal (b) and sagittal (c) planes. (a) The meningioma inserted on the right side but not across the midline. The tumor displaces the neuraxis antero-laterally and creates a large surgical corridor. (d-f) Postoperative CT-scans, after complete resection of the tumor through a postero-lateral approach. (d) The extension of the C1 laminectomy. The white arrow indicates the lateral limit with a C1 lateral mass left intact. The access is obtained on the base of insertion as demonstrated by the arrow direction. The laminectomy has been extended over the midline (black arrow) for preventing stretching of the neuraxis on the bone edge during the resection. (e) The size of the craniotomy. Black arrow and arrowhead show respectively the right and left vertebral arteries. (f) shows the vertebral artery V3 and V4 segments courses on a 3D reconstruction. The arrow indicates the V3-V4 junction. LM: C1 lateral mass. TP: C1 transverse process. Modified with permission.