MENINGIOMA OF THE FORAMEN MAGNUM - A SERIES OF 40 CASES

BACKGROUND Surgical treatment of foramen magnum meningiomas (FM mening iomas) has been improved by the recently developed posterolateral and anterolateral approaches, The choice of these approaches and the exten t of bone resection, however, need to be defined according to the tumo r location. METHODS Over a short period (1980-1993), 40 cases of FM me ningiomas were treated either by the posterolateral (N = 31), the ante rolateral (N = 5), or the midline posterior approaches (N = 4). The ch oice of surgical technique (surgical approach, extent of bone drilling , and dural opening) was made according to the tumor location, which i s defined by three parameters: the horizontal plane (anterior N = 18, lateral N = 21, and posterior N = 1); the vertebral artery (above N = 4, below N = 20, and on both sides N = 16); the dura mater (intradural N = 24, extradural N = 2, and intraextradural N = 4). RESULTS Intradu ral anterior and lateral FM meningiomas were operated by the posterola teral approach. The bone drilling was limited either to the occipital condyle or to the lateral mass of the atlas, depending on whether the tumor location is above or below the vertebral artery, respectively. I ntradural posterior meningiomas were treated by the midline posterior approach. FM meningiomas with an extradural component were resected by the anterolateral approach alone or combined with a midline posterior approach. The rate of complete resection was 94% for intradural FM me ningiomas and 50% for the extradural ones, FM meningiomas with an extr adural component generally have aggressive features invading the adjac ent bone and soft tissues; this explains the difficulty of performing a complete resection. The clinical condition improved in 90%, worsened in 7.5%, and did not change in 2.5%. The worsened group consisted of three deaths (one case of air embolism, one case of pulmonary embolism , and one case with preoperative coma and tetraplegia). Similar result s were obtained in both anterior and lateral locations. CONCLUSION FM meningiomas can be completely and safely removed in most cases, using an appropriate surgical technique. The technique must be chosen after precise and correct analysis of the tumor location. The lateral approa ches are very effective in the treatment of lateral and anterior FM me ningiomas. (C) 1997 by Elsevier Science Inc.