En plaque meningioma

Last revised by Hidayatullah Hamidi on 16 Nov 2023

En plaque meningiomas refer to a specific macroscopic appearance of meningiomas characterized by diffuse and extensive dural involvement, usually with extracranial extension into calvarium, orbit, and soft tissues. These tumors are thought to have a collar-like or sheet-like growth along the dura mater, different from the usual globular meningiomas.

See the article on meningiomas for a broad discussion on this entity.

There is no absolute and foolproof way of defining an en plaque meningioma from a flattish globular meningioma with an extensive dural tail (although it is important to note that the dural tail does not actually contain tumor cells). Furthermore, as en plaque meningiomas often have dramatic osseous involvement these tumors are often (erroneously) termed intraosseous meningiomas, a term which should probably be reserved for primary intraosseous meningiomas (i.e. those without intracranial extension). 

En plaque meningioma accounts for 2–9% of all meningiomas 5. It is 3 to 6 times more common in females with mean age of presentation 40–50 years 5.

The most common presenting symptom is proptosis. Besides, patients can present with headache, ptosis, diplopia, and unilateral visual impairment 5.

Although locally invasive, this tumor presentation usually corresponds to a WHO CNS grade 1 meningioma. Meningothelial cells are known to invade and expand the calvarial bones promoting local bone thickening. The extensive hyperostosis, which is frequently seen, is associated with infiltration of the medullary spaces by whorls and syncytia of meningothelial cells 2.

En plaque meningiomas are primarily located in spheno-orbital region. Less common locations are cerebral convexity, temporal bone, and foramen magnum 6.

Both CT and MR imaging are useful to evaluate the extent of extradural and calvarial involvement. These tumors commonly occur in the sphenoidal ridge, calvarium or spinal region. 

Due to the extensive and invasive presentation of these tumors, sometimes closer to vital structures, complete resection is usually not achievable. Partial removal can lead to a higher chance of recurrence 2. 

En plaque meningioma was first described by Cushing and Eisenhardt in 1938 as a carpet-like tumor associated with hyperostosis, commonly involving the sphenoid ridge and orbit 5.

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