title: Extra-axial brain tumors.
abstract: Extra-axial brain tumors are the most common adult intracranial neoplasms and encompass a broad spectrum of pathologic subtypes. Meningiomas are the most common extra-axial brain tumor (approximately one-third of all intracranial neoplasms) and typically present as slowly growing dural-based masses. Benign meningiomas are very common, and may occasionally be difficult to differentiate from more aggressive subtypes (i.e., atypical or malignant varieties) or other dural-based masses with more aggressive biologic behavior (e.g., hemangiopericytoma or dural-based metastases). Many neoplasms that typically affect the brain parenchyma (intra-axial), such as gliomas, may also present with primary or secondary extra-axial involvement. This chapter provides a general and concise overview of the common types of extra-axial tumors and their typical imaging features.
authors.affiliation: Division of Neuroradiology, Department of Radiology, Massachusetts General Hospital, Boston, MA, USA. Electronic address: orapalino@partners.org.
authors.forename: Otto
authors.initials: O
authors.lastname: Rapalino
authors.affiliation: Department of Radiology and Radiological Sciences, Uniformed Services University of the Health Sciences, Bethesda, MD, USA.
authors.forename: James G
authors.initials: JG
authors.lastname: Smirniotopoulos
mesh_terms: D001932:Brain Neoplasms / Q000145:classification* / Q000000981:diagnostic imaging* / Q000453:epidemiology / Q000628:therapy; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008577:Meningeal Neoplasms / Q000000981:diagnostic imaging / Q000628:therapy; D008579:Meningioma / Q000000981:diagnostic imaging / Q000628:therapy; D059906:Neuroimaging; D000072356:Parenchymal Tissue / Q000473:pathology
keywords: dural-based mass; extra-axial brain tumor; meningiomas; metastasis; neurofibroma; peripheral nerve sheath tumors; schwannoma; solitary fibrous tumor