The Foramen Magnum area (F.M.) is a complex region with many different pathologies that may develop either intradurally or extradurally. The former mainly include meningiomas (M) and neurinomas (N), while the latter corresponds to chordomas (Ch) and bone tumors (BT). Altogether these pathologies are very rare. The most common type (M) accounts for less than 0.5% of the intracranial tumors and 2.5% of the intraspinal tumors. In Table 1 the distribution of F.M. tumors in our personal series is given. Meningiomas account for about 70% of the intradural tumors and for 40% of all F.M. tumors; they represent 6.5% of posterior fossa M, 1.5% of cranial M, 12% of spinal M and 42% of cervical M. Neurinomas include C1 and C2 spinal nerve roots N and XI and XII cranial nerve N. The C2 N is the most frequent and represents 5% of spinal N and 20% of cervical N. Chordomas are most frequently located in the sacrum (40%), at the skull base (38%) and along the spine (22%). In our series Ch at the cranio-cervical junction (CCJ) level are quite predominant among skull base (65%) and cervical (85%) locations. However, there is certainly a bias related to our referral process. In Wellinger series, F.M. Ch accounts for 30% of cervical Ch and 12% of all spinal Ch. Then bone tumors (BT) (16% of all F.M. tumors) includes metastases (35% of BT) and primary BT of many different types; the most frequent ones are osteoid osteoma, chondrosarcoma, aneurysmal cyst and plasmocytoma.
