Meningiomas

Abstract

Meningiomas are a common nonglial neoplasm that can involve many areas of the central nervous system. Various clinical syndromes and symptoms are found to be associated with meningiomas resulting from their anatomic locations. These tumors can present with an array of imaging features seen in both common and uncommon types of meningiomas. Familiarity with their multitude of clinical presentations and imaging fi ndings can greatly enhance a radiologist's interpretation of these common tumors.An extra-axial mass derived from meningothelial cells, meningiomas have a strong predilection for occurrence in women with 65% of them occurring in women aged 40 to 50 years. The converse is true in the rare pediatric occurrence of meningioma, with 1.5% of all meningiomas found predominantly in boys by the age of adolescence. 1 Overall, meningiomas account for approximately 15% of all symptomatic intracranial neoplasms and 33% of all asymptomatic intracranial neoplasms noted at autopsy.The most recognized classifi cation of meningiomas is based on the World Health Organization (WHO) grading system, which recognizes 15 different histologic subtypes ( Table 1). The microscopic differentiation of the subtypes usually is only able to be determined upon pathologic correlation, not by imaging. The macroscopic variations of meningiomas, encountered by radiologists, often can be categorized into 2 forms: en plaque and globose. En plaque meningiomas present as an extensive region of dural thickening, whereas globose meningiomas present as a rounded, extra-axial mass. Radiographically, meningiomas are classifi ed by their locations, each presenting with varying prevalence and associated clinical symptoms based on location.The rare en plaque meningioma underlies the inner table of the skull and is capable of infi ltrating the dura mater and the overlying bone. Its permissive nature to infi ltrate presents a diagnostic dilemma for the radiologists, especially in noncontrast imaging examinations. Secondary clues of invasion, such as hyperostosis, are quite often absent or nonindicative of the extent of tumoral invasion (Figure 1).Falcine and parasagittal meningiomas are the most common by location 1 (Figure 2). These meningiomas can be further divided into anterior, middle, and posterior thirds to better explain the patient's clinical presentation. Meningiomas occurring in the middle one third of the falx commonly present with focal seizures, and sensory and motor loss that usually begins in the lower extremities. 1 By contrast, meningiomas along the anterior third of the falx, sagittal sinus, or anterior skull base have an insidious onset, presenting with headaches. 1 As a result, these latter meningiomas often are V o l u m e 3 7 • N u m b e r 2 4 N o v e m b e r 3 0 , 2 0 1 4Lippincott Continuing Medical Education Institute, Inc., is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians. Lippincott Continuing Medical Education Institute, Inc., designates this endu...