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Findings: Image #1 is a noncontrast enhanced axial CT image through the head demonstrating an approximately 4 x 6 cm mass within the subfrontal region. In addition, there is effacement of the basal cisterns.
Image #2 is a post contrast enhanced CT image through the same region demonstrating diffuse homogeneous enhancement of this mass.
Image #3 is an image from a selective angiogram of the internal carotid artery circulation demonstrating a fine vascular stain supplied by the anterior ethymoidal branches of the ophthalmic artery. The anterior cerebral arteries are displaced superiorly.
Diagnosis: Meningioma.
Discussion: Meningomas are solid, well-marginated benign lesions originating from the meninges. These tumors account for approximately 20% of adult brain tumors. They occur predominantly in middle-aged patients with a female preponderance. The most common sites of origin include the bilateral convexities, parasagittal regions, parafalcine, sphenoid wing, olfactory groove, and suprasellar region. They uncommonly arise infratentorially (approximately 10%). Most meningomas are homogeneously solid tumors, but there may be on occasion foci of necrosis as well as scarring, cystic degeneration, or calcification.
Nonenhanced computed tomography generally demonstrates a homogeneous mass that is isodense to intracranial parenchyma. Post contrast enhanced scans demonstrate diffusely homogeneous enhancement. In addition, there may be a broad-based dural tail where it abuts the dural margin. The magnetic resonance imaging characteristics of meningioma are generally characterized by isointensity to relative hypointensity on T1 weighted images to the contiguous gray matter. T2 weighted images generally demonstrate slightly increased signal intensity in relationship to the contiguous gray matter. There is relatively little associated vasogenic edema in relationship to the size of the lesion, likely secondary to its slow-growing nature. Post Gadolinium enhanced MR images demonstrate homogeneously intense enhancement. In addition, the enhancing dural tail may also be identified. Although meningiomas are histologically benign, they may invade surrounding structures including the dura and contiguous bony structures. Meningiomas may produce a hyperostotic reaction. This is a nonspecific finding which may also be produced by metastatic carcinoma. On rare occasions, the meningioma may completely penetrate the calvarium to invade the scalp. Meningiomas may occasionally have an atypical appearance and atypical enhancement pattern secondary to necrosis, scarring, previous hemorrhage, or fat deposition.
References:
Haaga, JR. Computed Tomography and Magnetic Resonance Imaging
of the Whole Body. Mosby, St. Louis;1994:198-202.
Latchaw RE. MR and CT Imaging of the Head, Neck and Spine. Mosby,
St. Louis;1991:509-525.
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