Extra-axial brain tumors

Abstract

Meningiomas, schwannomas, metastases, maldevelopmental cysts, epidermoids, dermoids and bone tumors represent the vast majority of extra-axial brain tumors. The location of extra-axial brain tumors affects treatment planning and predicts their prognosis. Computed tomography and particularly magnetic resonance imaging are used for diagnosis and localization. In this article, the imaging findings of the extra-axial brain tumors are discussed.Keywords Extra-axial . Brain tumors . MRI . Meningioma . Schwannoma Extra-axial tumors are the tumors of extracerebral location. They are usually benign. The location of brain tumors affects treatment planning and predicts their prognosis. The multiplanar capability of MR imaging makes it the best technique in the evaluation of extra-axial brain tumors. Meningiomas are the most common exta-axial neoplasms in the supratentorial compartment. Other extra-axial neoplasms are: schwannomas, metastatic lesions, arachnoid cysts, epidermoids, dermoids, chordomas and eosinophilic granulomas. MeningiomasMeningiomas are vascular, non-glial tumors of the central nervous system arising from meningothelial (arachnoidal) cells. They generally receive their blood supply from branches of the external carotid arteries, although large tumors will also recruit branches from the internal carotid arteries [1,2]. Meningiomas are the most common non-glial primary CNS tumors and the most common extra-axial intracranial tumors. The relative frequency of meningiomas regarding all intracranial tumors varies between 15% [1, 3, 4] and 20% [1,5,6]. They are encountered in middle-aged adults and are more common in women than in men. Childhood meningiomas are uncommon and represent 1-4.2% of central nervous system tumors and 1.5-1.8% of all intracranial meningiomas [7][8][9][10][11].The presenting signs and symptoms of meningiomas, when neurofibromatosis is excluded, are related to the tumor location and size, they are often non-specific and vague, primarily related to brain compression and edema from the adjacent neoplasm [1,12]. Signs of increased cranial pressure (nausea, headache, vomiting) are found in 50% of the patients. Confusion, focal weakness and seizures are the most common symptoms while paresis is the most frequently found physical sign [1,13,14]. Headache has been reported as the most common single presenting symptom, found in 36%, while normal physical examination has been reported in 26% of patients [12].The most common locations of meningiomas in descending order of frequency are: convexity meningiomas 20-34%, parasagittal 18-22%, sphenoid and middle cranial fossa 17-25%, frontobasal 10% and posterior fossa 9-15%.

Usefulness of Dual-Energy Computed Tomography Imaging in the Differential Diagnosis of Sellar Meningiomas and Pituitary Adenomas: Preliminary Report

“…The vast majority of the CT studies of intracranial tumors have focused on glialneoplasms. Only some articles have reported the usefulness of CT in the differentiation of various extra-axial tumors, especially meningiomas [9]. Furthermore, most of the studies concerning intracranial tumors, draw special attention to qualitative assesment without quantitative parameters.…”

Current Clinical Brain Tumor Imaging

“…For example, extra-axial tumors such as meningiomas, schwannomas, and skull base tumors can generally, but not always, be differentiated from intra-axial tumors based on associated interposition of cerebrospinal fluid, vessels, or dura between the mass and cortex. 15 Similarly, the number of lesions is an important consideration as multiple lesions suggest metastatic disease or non-neoplastic processes such as demyelination, inflammation, or infection. 9,16 Finally, several imaging characteristics suggest tumor subtypes.…”

Glioblastoma Presenting with the Radiological Features of a Meningioma: A Case Report and Literature Review

“…Determining whether intracranial masses are intra-or extra-axial is very important as this affects the diagnosis, treatment plan, and prognosis. Extra-axial masses include meningiomas, schwannomas, metastatic lesions, arachnoid cysts, epidermoids, dermoids, chordomas, and eosinophilic granulomas 5,15) . The characteristic radiological features differentiating extra-axial from intra-axial masses include local bone changes, white matter buckling (inward compression of the gray-white junction), pseudocapsule (signal void of the dura or displaced vessels), CSF cleft (CSF or cortical vessels entrapped between the tumor and underlying cortex), and dural tail sign (enhancement of the dura infiltrating away from the lesion) 2,5,6,9,15) .…”