En plaque meningiomas refer to a specific macroscopic appearance of meningiomas characterised by diffuse and extensive dural involvement, usually with extracranial extension into calvarium, orbit, and soft tissues. These tumours 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.
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Terminology
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 tumour cells). Furthermore, as en plaque meningiomas often have dramatic osseous involvement these tumours are often (erroneously) termed intraosseous meningiomas, a term which should probably be reserved for primary intraosseous meningiomas (i.e. those without intracranial extension).
Epidemiology
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.
Clinical presentation
The most common presenting symptom is proptosis. Besides, patients can present with headache, ptosis, diplopia, and unilateral visual impairment 5.
Pathology
Although locally invasive, this tumour 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.
Location
En plaque meningiomas are primarily located in spheno-orbital region. Less common locations are cerebral convexity, temporal bone, and foramen magnum 6.
Radiographic features
Both CT and MR imaging are useful to evaluate the extent of extradural and calvarial involvement. These tumours commonly occur in the sphenoidal ridge, calvarium or spinal region.
Treatment and prognosis
Due to the extensive and invasive presentation of these tumours, sometimes closer to vital structures, complete resection is usually not achievable. Partial removal can lead to a higher chance of recurrence 2.
History and etymology
En plaque meningioma was first described by Cushing and Eisenhardt in 1938 as a carpet-like tumour associated with hyperostosis, commonly involving the sphenoid ridge and orbit 5.
Differential diagnosis
neuroblastoma craniocerebral metastasis: associated with sunburst periosteal reaction
primary intraosseous meningioma: no dural involvement
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