George B, Lot G, Velut S, Gelbert F, Mourier K L
Département de Neurochirurgie, Hôpital Lariboisière, Paris.
Neurochirurgie. 1993;39 Suppl 1:1-89.
Since what seems to be the first reported case of foramen magnum (F.M.) tumor by Hallopeau in 1874, literature on tumoral pathology of this region is rather scarce; beside reports of single cases or short series, there are very few large series and most of them are not recent (Meyer et coll., Yasuoka et coll., Guidetti and Spallone). The present report includes 230 cases of extramedullary tumors collected from 21 french departments over the last ten years (series of the French Speaking Society of Neurosurgery = S.N.C.L.F. series). Delimitation of what is called the F.M. region is rarely given in the literature. In this report, the inferior limit is put at the C2 level and the superior one at the ponto-medullary junction and the lower third of the clivus. To belong to the F.M. region, tumor must have its main part or its insertion within these limits even if it extends beyond them. On the contrary, if the gross development is out of these limits but with some extension into the F.M. region, the case is rejected. A chapter of this report deals with the anatomy of the F.M. with emphasis on the points useful for the management of the tumors. Some details are given on the dimensions of the different parts of the F.M. as given by anatomical studies and also by measurements on C.T. scanner and M.R.I. including during flexion and extension of the head. The S.N.C.L.F. series is then analyzed as a whole. It includes 106 meningiomas (M), 49 neurinomas (N), 28 chordomas (Ch), 32 osseous tumors (T.Os) (19 primary and 13 metastasis) and 15 cases considered as uncommon tumors. (T. Part.) (4 melanomas, 3 hemangioblastomas, 3 dermoid or epidermoid cysts, 2 ependymomas, 1 cavernoma, 1 angiomyolipoma and 1 cholesterin cyst). Mean age is 47 years, with a sex ratio F/M of 1.5/1. Duration of symptoms before diagnosis is of 27 months. Topography is classified into 3 groups anterior (70 cases), lateral (142 cases) and posterior (24 cases). A particular definition is given to these localizations, essentially referring to surgical difficulties and specially for meningiomas. The localization of a tumor is defined by the point of attachment to any structure (dura, spinal root, spinal cord); anterior tumors are attached to the F.M. on both sides of the midline; lateral tumors between the midline and the dentate ligament and posterior ones behind the dentate ligament. According to this way of classification, N are always lateral even if they present anterior or posterior extensions.(ABSTRACT TRUNCATED AT 400 WORDS)
