Multiple meningiomas: Epidemiology, management, and outcomes.

Meningiomas are the most common nonmalignant brain tumor in adults, with an increasing incidence of asymptomatic meningiomas diagnosed on more ubiquitous neuroimaging. A subset of meningioma patients bear 2 or more spatially separated synchronous or metachronous tumors termed "multiple meningiomas" (MM), reported to occur in only 1%-10% of patients, though recent data indicate higher incidence. MM constitute a distinct clinical entity, with unique etiologies including sporadic, familial and radiation-induced, and pose special management challenges. While the pathophysiology of MM is not established, theories include independent origin in disparate locations through unique genetic events, and the "monoclonal hypothesis" of a transformed neoplastic clone with subarachnoid seeding precipitating numerous distinct meningiomas. Patients with solitary meningiomas carry the risk of long-term neurological morbidity and mortality, as well as impaired health-related quality of life, despite being a generally benign and surgically curable tumor. For patients with MM, the situation is even less favorable. MM should be regarded as a chronic disease, and in many cases, the management goal is disease control, as cure is seldom possible. Multiple interventions and lifelong surveillance are sometimes necessary. We aim to review the MM literature and create a comprehensive overview, including an evidence-based management paradigm.