Giant intraosseous meningioma mimicking fibrous dysplasia

Abstract

We illustrate a case of a giant primary intraosseous meningiomas (PIMs) with optic nerve compression treated by partial resection. A 48-year-old female presented with visual disturbances exophthalmus, diplopia and eye pain due to optic nerve compression. The patient had a past history of fibrous dysplasia treated surgically with partial resection by ENT in 2010. Histology confirmed the diagnosis. Two years later she presented with further decrease in visual acuity and diffuse hyperostosis. In this context she underwent a neurosurgical procedure consisting in craniotomy and further partial resection of the lesion including optic canal decompression. The second pathological examination demonstrated an extensive meningioma (WHO grade I) of the skull base.We recommend that in cases of diffuse hyperostosis the differential diagnosis include diffuse intraosseous meningioma. If complete surgical resection is not achievable, a biopsy to confirm the diagnosis is recommended. Treatment options include complete or partial resection followed by adjuvant radiotherapy.Key Words: Skull base, Meningioma, Hyperostosis, Fibrous dysplasia CASE REPORTA 48-year-old woman presented with a 3-year history of progressive right sided visual disturbance, exophthalmus, diplopia and eye pain. The patient underwent a cranial CT scan which showed a diffuse bilateral frontal and skull base hyperostosis, especially evident on the right side, and extending bilaterally from the sphenoid bones, down to the clinoid processes, orbits, temporal bones and the right frontal bone as seen in Figure 1. The right optic nerve was displaced with narrowing of the optic canal. These findings were consistent with fibrous dysplasia. Diffuse hyperostosis could also be consistent with an osteosarcoma, although this was less likely. The mass effect of the tumor involving both orbits caused compression of the eye muscles with subsequent exophthalmos, also more evident on the right side. The general practitioner referred the patient to an ophthalmologist who diagnosed exophthalmos with compressive optic nerve atrophy, decreased vision and secondary glaucoma. The ophthalmologist then referred the patient to an ENT doctor.The patient underwent surgical decompression of the right orbit via a transethmoidal, transsphenoidal and transpalpebral approach. During the operation, visualization of the orbital content was inadequate and bleeding from the bone prevented completion of the planned operation. The ENT suggested a second operation via a right subfrontal craniotomy to further decompress the orbit and the optic nerve. The first histopathological analysis seemed to confirm the suspicion of fibrous dysplasia and the patient was discharged. Ophthalmological and radiological follow-up was conducted via CT and MRI.