Primary extradural intra-orbital meningioma in a Chinese girl.

PRIMARY intra-orbital meningiomas are rather uncommon, and primary intraorbital meningiomas unattached to the optic nerve sheath are decidedly rare. Scarpa (1816) was quoted by Byers (1901) as being the first to have reported an intraorbital meningioma. Goar (1926) and Mayer (1928) estimated the number of intra-orbital meningiomas in the literature at 40, but there was no clear indication in many of these as to whether they were primary or secondary. Schreck (1939) studied 15 of these intra-orbital tumours removed at the Heidelberg University Hospital. Cushing and Eisenhardt (1938) saw only one in their series of 313 meningiomas. Craig and Gogela (1949) wrote a brilliant paper quoting 17 primary and 35 secondary intra-orbital meningiomas. Primary intra-orbital meningiomas with no attachment to the optic sheath are rarer still and their pathogenesis poses a challenging problem. Only a few such tumours have been reported. Schreck (1939), in his Heidelberg studies, concluded that free-lying meningiomas need not arise from the optic sheath. Out of the 17 primary intra-orbital meningiomas of Craig and Gogela (1949), 3 were foraminal, 9 arose from the optic sheath, and 5 "lay more or less freely either within or outside the muscle cone or were attached firmly to the periorbita". The case reported here is of a meningioma occurring outside the muscle cone and firmly attached to the periorbita of the medial wall of the orbit, and has a nerve coursing through it.