Primary Intraosseous Meningioma of the Calvarium: A Systematic Review and Meta-analysis

Introduction: Primary intraosseous meningiomas (PIM) of calvarial origin are a small subset of meningiomas that arise from and occur within the calvarial bone. Its definition is often confused with other forms of non–dural-based intracranial meningiomas, which has made previously published retrospective reviews heterogenous, nonspecific and sometimes inaccurate. We present a systematic review and meta-analysis of primary calvarial intraosseous meningiomas. To our knowledge, this is the first comprehensive systematic review of calvarial PIM.

Methods: Using a systematic search protocol that included databases such as PubMed, Web of Science and Embase, we extracted all human studies on primary intraosseous meningiomas published from inception to December 2017. The search protocol was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. This systematic review includes case reports and retrospective review articles that specifically described PIM, and included variables such as patient’s age, sex, tumor location, size, presenting symptoms, treatment modality, extent of resection, follow-up, recurrence and histopathology. Meningiomas of cutaneous origin, extradural but not intraosseous origin, primarily orbital wall or roof meningiomas, those of paranasal sinus origin, middle ear, nose or throat were excluded.

Results: A total of 83 articles from 21 different countries were compiled, and comprised of 78 case reports, 1 case series and 4 retrospective reviews. 142 patients with PIM of calvarial origin were analyzed. The most common tumor location was in the frontal and parietal calvarium, with frontal bone being the most common occurrence in 20.4% of the cases, parietal bone in 16.9%, and a combination of the frontoparietal bone in 12.6% of the cases. The most common symptom was an identified mass lesion, which occurred in 56.4% of the patients, and it was typically a growing mass. Surgical resection alone was the predominant modality of treatment, occurring in 92.3% of the cases. Only 1.5% of patients were treated with radiation alone, and 6.2% received a combination of surgery and radiation. Gross-total resection was achieved in 82% of cases, and subtotal resection in 18%. The mean postoperative follow-up interval was 20 months. Meningothelial meningioma was the most common diagnosis at 42.6%. Atypical meningioma was diagnosed in 5.4% of the patients and malignant meningioma occurred in 3.9%. 48.5% of tumors were osteoblastic, 39.5% were osteolytic, and 12% were mixed. Recurrence was reported in 10% of the patients. The complication rate was 6.3%, and there was a 2.1% patient mortality reported.

Conclusion: Primary intraosseous meningioma of calvarial origin is a unique subset of non–dural-based intracranial meningiomas. Osteolytic meningiomas make up a higher than previously reported percentage of primary calvarial intraosseous meningiomas, and they should be considered in the differential for lytic skull lesions. Surgical resection remains the overwhelming treatment of choice for primary calvarial intraosseous meningiomas, and it has a high gross-total resection rate and low risk of complications and mortality.