Primary orbital meningioma: a study of six cases at a single institution.

Primary orbital meningioma is a rare tumor of the anterior visual pathway and constitutes approximately 2% of all orbital tumors and 1-2% of all meningiomas. The differentiation from secondary orbital meningioma of intracranial origin is sometimes difficult on image. As the tumor often leads to visual loss if left untreated and surgical intervention inevitably causes morbidity, the timing and modality of treatment are very important. We carried out the study involving six cases (mean age: 42.7 years, male to female ratio: 1:5) of primary orbital meningioma to further elucidate its behavior. The clinical signs and symptoms, diagnosis, treatment strategies, and follow-up information are recorded for all cases. The most frequent initial symptoms were visual complaints (100%) and proptosis (67%). In five cases, the diagnosis was based on pathologic findings and the tumors were all grade I meningiomas. In one case, however, the diagnosis was based on radiographic and clinical findings, lacking histologic confirmation. Five patients were operated on, four underwent tumor removal, and one received eyeball exenteration. One patient was treated with Novalis radiotherapy. The mean follow-up period was 8.8 years (range from 9 months to 15 years). All patients experienced loss of vision during the course without exception. No recurrent tumor was found in five cases during follow-up. In case 5, whose eyeball was exenterated, developed recurrent meningioma 7 years later. She received radiotherapy but the tumor was out of control. She expired 8 years after eyeball exenteration. The primary orbital meningioma is aggressive in behavior despite its benign histopathologic features. Loss of vision is frequently seen even after treatment. The tumor could be fatal if surgery and radiotherapy fail to control its intracranial extension.