Foramen Magnum Tumours: Posterior Approaches and Outcome

Abstract

A variety of extra- and intradural lesions at the level of the foramen magnum exist. These include chordomas, meningiomas, and schwannomas, respectively. The particular challenge of the treatment of these tumours lies in the close proximity and/or involvement of highly sensible neurovascular structures such as the lower brainstem, the lower cranial nerves, and the V3 and V4 segments of the vertebral arteries. Depending on size and extension of the tumours, preoperative diagnostics include thorough clinical neurological examination, ENT exams, and electrophysiological testing of the motor and sensory pathways. On the imaging side, osseous anatomy is visualized by high-resolution CT scanning of the craniovertebral junction—complemented by structural MRI, including MRA and venography. The surgical approach should be planned on the basis of detailed 3D analysis of the individual patho-anatomical situation, related to the precise localization of the tumour in relation to the foramen magnum. The standard midline or lateral suboccipital approach, with or without (hemi-)laminectomy of C1, is most frequently used as it offers access to the majority of these lesions. Occasionally, mechanical instability might ensue and thus render osteosynthesis necessary. Surgery is performed under intra-operative neurophysiological monitoring whenever manipulation of the spinal cord at the cervicomedullary junction is expected to happen. Most frequent complications are related to difficulties in attaining watertight dural closure. But, good functional outcome can be achieved frequently, with serious vascular or neural complications being the exception.