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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 sub group 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. 

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 verebral 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 hyper intense
  • T1 C+ (Gd): as with conventional meningiomas typically tends to have unform 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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