Clinical Profile:

A 54 year old man came with the complaints of a huge occipital swelling associated with headaches. Due to the swelling, the patient had difficulty lying down in the supine position and constantly felt heaviness in the head. He gave history of trivial trauma to the occiput a year ago. Thereafter he has noticed a progressively increasing painless swelling over that region.

Figure 1

The large occipital swelling with a shiny skin

Radiological findings:

Figure 2

The lateral skull radiograph shows a large lytic lesion involving the occipital bone with ill-defined margins, wide zone of transition & no marginal sclerosis. There is interrupted spiculated periosteal reaction & a large soft tissue mass associated with the lesion. Spicules of lysed bone were seen within the swelling

Figure 3

Plain and contrast enhanced CT scans show a large ,extra axial, intensely enhancing heterogeneous soft tissue mass measuring approximately 6.x114x11cin the occipital region causing destruction of the occipital & parietal bones. on both sides. The margins of the lysed bone show spiculated periosteal reaction with fragments of the lysed bone seen within the soft tissue mass. Anteriorly the lesion extends along the dura into occipital and left parietal lobe with a heterogeneously enhancing lesion within the left posterior parasagittal parietal lobe with perilesional oedema.. There is invasion and thrombosis of venous sinuses at the torcula and superior sagittal sinus.

Figures 4, 5

The T1 weighted and T2 weighted axial sections of an MRI brain show predominantly T2 intermediate and T1 isointense extra axial lesion measuring 7x10x12cm (ith few T2 bright areas along the posterior aspect aspects of bilateral parietal and occipital bone causing bone erosion and extending up to the skin and subcutaneous plane.. There is perikesional edema. On contrast enhanced T1 axial and T2 axial sections of brain the lesion shows intense homogenous post contrast enhancement. The intracranial portions appear to be extra axial in nature.

Figure 6

External carotid angiogram shows a hypervascular mass. Post embolisation images (below) show substantial reduction in vascularity, The major feeders to the tumour mass were from occipital arteries.

Radiological Diagnosis:

Malignant tumor from the occipital bone / Atypical meningioma

Pathological diagnosis:

An ultrasound guided biopsy of the lesion showed primary intraosseous menngioma

Course in the hospital:

Partial excision of the tumor was performed. The intracerebral part will be excised at a second stage, The patient's clinical condition is unchanged. Post-operatively, the patient has developed flap necrosis. No new symptoms have developed

Figure 7

The excised extracerebral part of the tumor

Discussion:

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 tumors and are more prone to develop malignant features than do intracranial meningiomas. . In our case, we describe a case of post traumatic PIM of the occipital bone with atypical pathology, which did not metastasize but infiltrated the dural and underlying cerebral hemisphere. Primary intraosseous meningioma (PIM)" is a subset of extradural meningiomas that arise in the bone.

• Many different hypotheses exist regarding the origin of primary extradural meningiomas. The 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. traumatic misplacement & entrapment of meningothelial cells into suture or fracture lines has also been speculated as the probable cause.

• In our case, the patient presented with occipital intraosseous meningioma post trauma to occiput, likely secondary to the speculated hypothesis of traumatic entrapment of meningothelial cells into the lambdoid or posterior part of sagittal suture.

• In the literature, only five of the 36 cases of primary intraosseous meningioma had a history of trauma in the region of the tumor site.

• Crawford et al., in a review of the literature, found that radiographic evidence of hyperostosis appeared in 59% of PIMs, whereas 32% showed osteolytic changes in the surrounding bone, and 6% revealed mixed features of both osteolysis and hyperostosis.

• The differential diagnosis of an extra axial osteolytic lesion of the skull with soft tissue mass include solitary fibrous tumor of the dura (hemangiopericytoma), intraosseous meningioma, chondrosarcoma, osteogenic sarcoma, or metastatic cancer.

• PIMs with an osteolytic radiographic appearance are more likely to be malignant. They progress rapidly and invade the surrounding structures and show anaplastic or malignant histopathology.

• CT with bone window is necessary in the detection of the tumor, cortical destruction & both intra and extraosseous extension.

• Treatment of choice is total tumor removal with a wide surgical resection followed by cranial reconstruction.

• If only subtotal resection is possible due to involvement of critical structures, the residual tumor should be followed radiologically.

• Adjuvant radiation therapy is recommended if the residual lesions are symptomatic or show evidence of progression.

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

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.

Acknowledgement:

We are grateful to the Department of Neurosurgery at our institution for providing an image of the operative specimen.