Primary intraosseous meningioma classification [Neurosurgery Wiki]

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====== Primary intraosseous meningioma classification ======

Lang et al. 
((Lang FF, Macdonald OK, Fuller GN, DeMonte F: Primary extradural meningiomas: A report on nine cases and review of literature from the era of computerized tomography scanning. J Neurosurg 93(6):940-950, 2000))
classified [[primary intraosseous meningioma]] into 3 types in order to prevent any confusion: purely extra-[[calvaria]]l (type I), purely calvarial (type II), and calvarial with extracalvarial extension (type III).

[[Intraosseous lipomatous meningioma]]
((Kim L, Huang C, Morey AL, Winder MJ. Intraosseous lipomatous meningioma. Case 
Rep Neurol Med. 2015;2015:482140. doi: 10.1155/2015/482140. Epub 2015 Jan 26.
PubMed PMID: 25688309; PubMed Central PMCID: PMC4321083.))

Osteolytic intraosseous meningiomas are the rarest and very few cases have been reported. Given that many of these may develop signs of malignancy, early histological confirmation is important in order to ensure appropriate treatment. 

===== Type III intraosseous meningioma =====

Type III intraosseous meningioma is a very rare type of meningioma with extracranial extension. 

Su et al., reported a case of type IIIC [[intraosseous meningioma]] with invasion of the [[superior sagittal sinus]] and skull [[periosteum]]. A 67-year-old woman was admitted due to a mass on the left frontoparietal region for 4 years. [[Magnetic resonance imaging]] showed a [[skull tumor]] with invasion of the [[superior sagittal sinus]]. After [[partial resection]] of the [[tumor]], pathological and [[immunohistochemistry]] revealed that the epithelial meningioma derived from [[skull]] involved the skull [[periosteum]]. There was no enlargement of residual [[parasagittal]] tumor after 1 year of follow-up. The intraosseous meningioma in the present case was a rare benign tumor with good prognosis after surgery
((Su J, Ba Y, Liang S, Liu H. Type III Intraosseous Meningioma Invading Superior
Sagittal Sinus and Skull Periosteum. J Craniofac Surg. 2019 Mar 27. doi:
10.1097/SCS.0000000000005525. [Epub ahead of print] PubMed PMID: 30939563.
)).
----
A 78-year-old female with a slowly growing hard mass in the left parietal bone was admitted. Neurological findings were normal. Plain skull radiograph showed a 6 x 6 cm hyperostotic lesion in the left parietal bone. Bone window CT scan showed thickening and hyperostosis in the same area. MRI using Gd-DTPA showed heterogeneous enhancement of the intraosseous mass, and homogenous enhancement of the dura matter. And angiogram showed a tumor stain fed by the bilateral superficial temporal artery and the It-occipital artery. The tumor and the underlying dura mater were totally removed. Preoperative diagnosis was an osteogenic tumor, but histological examination revealed a transitional meningioma. We discussed the development and the classification of an ectopic meningioma and the mechanism of hyperostosis. We should be aware of the existence of intraosseous menigiomas mimicking osteogenic tumors
((Nanto M, Tsuji N, Miki J, Tanaka S, Uematsu Y, Itakura T. [A case of
intraosseous meningioma with extracranial progression having difficulty in making
a preoperative diagnosis]. No Shinkei Geka. 2005 Jan;33(1):51-6. Japanese. PubMed
PMID: 15678869.
)).

===== References =====