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Department of Radiology

Seth G.S. Medical College and K.E.M. Hospital, Mumbai , India

Case of the Month

< Case No. 58 : February 2025 >

Primary intraosseous meningioma

Contributed by : Anjali Methre

Other cases

Introduction :

Meningiomas are usually considered primary intradural lesions and are located along the meninges. By contrast, extradural meningiomas arise in locations other than the dura mater. “Primary intraosseous meningioma” (PIM) refers to a subset of extradural meningiomas that arise in bone. They compromise less than 2% of all meningiomas. These are usually mistaken for primary bone tumours and are more prone to develop malignant features than do intracranial meningiomas.

In this report, we describe a case of PIM of the parietal bone and sphenoid bone with atypical pathology, which did not metastasize but infiltrated the dura with mass effect on the underlying cerebral hemisphere.

Clinical Profile:

A 65-year old woman came with a painless swelling at the vertex since two years.

Initially the lesion was peanut-sized with a gradual increase in the size over two years.

There was no tenderness or erythema of the overlying . There was no discharge. On palpation the swelling was firm and non-fluctuant. (Fig. 1)

Fig 1

Clinical Image. A smooth, firm swelling over the vertex with no erythema of overlying skin.

Radiological findings :

Fig 2

Plain radiographs. The left frontal and ethmoid sinuses are opacified. The left innominate line and lesser wing of the sphenoid are eroded. A large ill-defined lytic lesion in the right high parietal region involving both inner and outer table measuring approximately 3 x 5cm

Fig 3

Ultrasonography: An ill-defined, heterogeneously hyperechoic lesion with irregular margins is seen at the right high parietal region measuring 4.5 x 4 cm. There is moderate internal vascularity (average PSV 12cm/sec). The overlying bone is irregular.

Fig 4

Plain CT scan.

A well-defined expansile intraosseous lesion in the right parietal bone measuring 4.1x3.8x3.1cm . The lesion shows predominantly bony matrix with multiple internal trabeculae. A similar lesion is seen in the left greater wing of the sphenoid bone causing displacement of the lateral rectus medially and the left globe anteriorly.

Fig 5

MRI.

There is a well defined soft tissue lesion in the right parietal bone with uplifting the periosteum and extension into the parietal epidural region. There is homogenous post contrast enhancement with dural tail.. Both the inner and outer tables of the skull are involved.

Fig 6

MRI.

A similar lesion is noted involving the left sphenoid wing pushing the left globe anteriorly and lateral rectus medially.

Radiological diagnosis:

Intraosseous meningioma / intraosseous haemangioma.

Management:

A wide surgical excision of the right parietal bone lesion was performed with cranial reconstruction. Histopathological examination showed few atypical cells. The lesion in the left greater wing of the sphenoid was not operated. Adjuvant radiotherapy and radiological follow up was advised.

Pathological diagnosis

Primary intraosseous meningioma.

Timeline:

Discussion

"Primary intraosseous meningioma (PIM)" is a rare subset of extradural meningiomas that arise in the bone. It accounts for only 1-2% cases of all meningiomas. [1] Many different hypotheses exist regarding the origin of primary extradural meningiomas. A commonly stated hypothesis is that they arise from ectopic meningocytes or arachnoid cap cells trapped in the cranial sutures during the molding of head at birth. [2] Traumatic misplacement & entrapment of meningothelial cells into sutures or fracture lines have also been speculated as the probable cause. About 13% cases of primary intraosseous meningioma give a history of trauma in the region of the tumour site. Radiographic evidence of hyperostosis appears in 59% of PIMs, whereas 32% show osteolytic changes in the surrounding bone, and 6% revealed mixed features of both osteolysis and hyperostosis. [3]

The differential diagnosis of an extra-axial osteolytic lesion of the skull with associated soft tissue mass include:

1. Solitary fibrous tumour of the dura (hemangiopericytoma)

2. Intraosseous meningioma

3. Chondrosarcoma.

4. Osteogenic sarcoma

5. Metastatic cancer.

PIMs with an osteolytic radiographic appearance are more likely to be malignant. They progress rapidly, invade the surrounding structures, and show anaplastic or malignant histopathology. [4] CT with a bone window is necessary to detect the tumour, cortical destruction, and both intra- and extraosseous extension.

The treatment of choice is total tumour removal with a wide surgical resection followed by cranial reconstruction. If only subtotal resection is possible due to the involvement of critical structures, the residual tumour should be followed radiologically. Adjuvant radiation therapy is recommended if the residual lesions are symptomatic or show evidence of progression. [5]

Recurrence was noted in 22% of the cases of benign PIMs found in the literature, and PIMs located at the skull base showed a higher recurrence rate than PIMs located along the convexity. On the other hand, a recurrence rate of 33% was reported in cases of tumours with atypical or malignant histological features. [6]

References:

1. Elder JB, Atkinson R, Zee CS, Chen TC. Primary intraosseous meningioma. Neurosurgical focus. 2007 Oct 1;23(4):E13.

2. Lang FF, Macdonald OK, Fuller GN, DeMonte F. Primary extradural meningiomas: a report on nine cases and review of the literature from the era of computerized tomography scanning. J Neurosurg. 2000 Dec;93(6):940-50. doi: 10.3171/jns.2000.93.6.0940. PMID: 11117866.

3. Yun JH, Lee SK. Primary osteolytic intraosseous atypical meningioma with soft tissue and dural invasion: report of a case and review of literatures. Journal of Korean Neurosurgical Society. 2014 Dec 31;56(6):509-12.

4. Borggreven, P., De Graaf, F., Van der Valk, P., & Leemans, C. (2004). Post-traumatic cutaneous meningioma. The Journal of Laryngology & Otology, 118(3), 228-230. doi:10.1258/002221504322928035

5. Crawford TS, Kleinschmidt-Demasters BK, Lillehei KO. Primary intraosseous meningioma: case report. Journal of neurosurgery. 1995 Nov 1;83(5):912-5.

6. Tokgoz N, Oner YA, Kaymaz M, Ucar M, Yilmaz G, Tali TE. Primary intraosseous meningioma: CT and MRI appearance. American Journal of Neuroradiology. 2005 Sep 1;26(8):2053-6.

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