Intraosseous meningioma

Intraosseous meningioma, also referred as primary intraosseous meningioma, is a rare subtype of meningioma that accounts for less than 1% of all osseous tumours. They fall under the subgroup of primary extradural meningiomas.

Terminology

It is important to note that this group of meningiomas does not include those intradural meningiomas which present with a intraosseous extension even when the intracranial (non-osseous component) is a minor feature of the mass. For example, en plaque meningiomas often have prominent hyperostosis or bony invasion. Some authors have suggested that this distinction is somewhat arbitrary 5, and it is certainly true that the terms en plaque meningioma and intraosseous meningioma are often used interchangeably. In the absence of a clearly nodular intra-cranial component, it is unclear if the distinction can be made on imaging, although en plaque meningiomas are considered far more common. 

Epidemiology

As with meningiomas in general there is recognised female predilection. 

Clinical presentation

Clinical presentation is usually due to mass effect, the manifestations of which will depend on the location. The calvarium and vertebral column are the most frequent sites 2. Presentations include:

  • palpable or visible bony mass
  • proptosis
  • cranial nerve / spinal cord compression
  • intracranial mass effect / hydrocephalus

Pathology

Thought to occur from trapped arachnoid meningothelial cap cells within cranial sutures during development. However despite this theory only a small proportion of intraosseous meningiomas actually occur in association with a skull suture 3.

Radiographic features

The majority ~65% are osteoblastic while ~35% are osteolytic 3. Due to this imaging appearances are non-specific. 

CT

The commoner osteosclerotic type tends to show diffuse sclerosis with bony expansion.

MRI
  • T1: may show an isointense extra axial mass component with the expanded bony component being low signal similar to the rest of the skull
  • T2: meningioma component is typically isointense to grey matter while a small proportion can be hyperintense
  • T1 C+ (Gd): as with conventional meningiomas typically tends to have an uniform avid contrast enhancement  

Treatment and prognosis 

They are generally benign and slow growing but there may be higher proportion of malignant change compared with standard meningiomas 3. Surgical resection with bone grafting may be performed in symptomatic cases.

Differential diagnosis

For osteoblastic type consider:

For osteolytic type consider:


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Article Information

rID: 9630
Section: Pathology
Tag: cases
Synonyms or Alternate Spellings:
  • Intraosseous meningiomas
  • Primary intraosseous meningioma
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    Case 1: with en plaque component
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    Case 2
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