LAUSR

http://dx.doi.org/10.1590/0100-3984.2017.0106 Benardo Carvalho Muniz1,a, Bruno Niemeyer de Freitas Ribeiro1,b, Nina Ventura1,c, Emerson Leandro Gasparetto1, Edson Marchiori2,d 1. Instituto Estadual do Cérebro Paulo Niemeyer – Departamento de Radiologia, Rio de Janeiro, RJ, Brazil. 2. Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, RJ, Brazil. Correspondence: Dr. Bernardo Carvalho Muniz. Instituto Estadual do Cérebro Paulo Niemeyer – Departamento de Radiologia. Rua do Resende, 156, Centro. Rio de Janeiro, RJ, Brazil, 20231-092. E-mail: [email protected]. a. https://orcid.org/0000-0003-1483-2759; b. https://orcid.org/0000-0002-1936-3026; c. https://orcid.org/0000-0003-2364-1612; d. https://orcid.org/0000-0001-8797-7380. representing approximately 14–20% of cases. The vast majority are intradural lesions, extradural lesions accounting for only 1–2%. Extradural meningiomas affect the cranial vault in 68% of cases, such lesions being referred to as primary intraosseous meningiomas (PIMs), which mainly affect the frontal and parietal bones, as well as the region of the orbit. Other common locations for extradural involvement are the subcutaneous tissue, paranasal sinuses, and parapharyngeal spaces, as well as, in rare cases, the lungs and adrenal glands. Unlike typical intradural meningiomas, which primarily affect females between the ages of 50 and 69 years and usually have a benign course, PIMs can affect either gender, have a peak incidence in the second decade of life, and are more likely to evolve to malignant degeneration. On CT, most PIMs (65%) present as expansile, osteoblastic bone lesions, with or without cortical destruction. On MRI, they commonly hypointense in T1and T2-weighted sequences, typically without significant contrast enhancement, as in the case reported here. However, in rarer cases, if a PIM presents as an osteolytic lesion on CT, an MRI scan can show a hypointense signal in T1-weighted sequences and a hyperintense signal in T2-weighted sequences, as well as contrast enhancement. Although PIMs do not present the dural tail sign that is often found in intradural meningiomas, there can be contrast uptake in the dura mater subjacent to the tumor due to venous stasis or to tumor invasion, as demonstrated in our case. There are inherent differences between CT and MRI, the former allowing better delineation of bone involvement, whereas the latter provides a better assessment of the soft-tissue involvement and extradural extent of the lesion. The differential diagnosis of osteoblastic PIM includes typical intradural meningioma with reactive hyperostosis, in which the meningeal component of the lesion is the most obvious. Other diagnoses that should be considered are metastases, plasmacytoma, fibrous dysplasia, osteoma, osteosarcoma, and Paget’s disease. In most cases of PIM, the treatment is total surgical resection, with subsequent cranial reconstruction. If the resection is partial, there should be radiological follow-up; if the disease has recurred or if the residual lesion has progressed, the next surgical procedure can be accompanied by adjuvant radiotherapy. In conclusion, although rare, PIMs should be considered in the differential diagnosis of bone lesions, especially when the lesions are osteoblastic and located in the cranial vault.