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Findings: On MRI a large approximately 7.8 x 5.8 cm in the anterior-posterior and transverse dimension extraaxial mass is seen arising from the dura in the region of the left frontal lobe. The mass appears isointense to gray matter on T1 weighted images and isointense to slightly bright on T2 weighted images and contains multiple flow voids. There is a significant associated mass effect and buckling of the underlying cortex. There is significant mass effect on the left lateral ventricle, inferiorly on the corpus callosum, and medially there is midline shift of approximately 1.2 cm to the right. There is no significant associated edema.
On cerebral angiogram, the left anterior cerebral artery is exhibiting round shift from left to right (round shift usually represents presence of an anterior/frontal mass adjacent to the anterior cerebral artery). The main blood supply to this tumor is from the anterior falcine artery arising from the left ophthalmic artery and the anterior division of the right middle meningeal artery off the external and carotid artery. On the delayed images of the cerebral angiogram in the venous phase, it is noted that the superior sagittal sinus is attenuated by the mass. This is felt to represent either effacement from the mass or direct invasion by the mass. Surgically, effacement of the superior sagittal sinus (SSS) carries a poor prognosis because the SSS cannot be sacrificed (as it can be when there is complete occlusion) without the additional risk of vascular infarctions.
Diagnosis: Left falcine meningioma.
Discussion: Most meningiomas arise from specialized meningothelial cells in arachnoid granulations. Multiple meningiomas occur in 1 to 9% cases and approximately 50% of these patients have neurofibromatosis 2 and therefore an abnormality on chromosome 22.
Meningioma is the most common nonglial primary CNS tumor accounting for 15-20% of primary neoplasms. The World Health Organization divides meningiomas into three basic categories: meningioma (common, typical, or benign) - 95%, atypical meningioma - 5%, and anaplastic or malignant meningioma 1-2%. The peak age is between 40 and 60, with a preponderance of females in about a three to one ratio.
Since meningiomas arise from arachnoid cap cells, they are typically found along dural sinuses and sutures. Most commonly, they are seen parasagittally (25%). Other locations include the convexity (20%), sphenoid ridge (15-20%), and olfactory groove (5-10%).
References:
Osborn A. Diagnostic Neuroradiology, Mosby; 1994:584-601.
Brant WE. Fundamentals of Diagnostic Radiology, 2nd Edition.
Williams & Wilkins; 1999:134-136.
Schwartz RB. Neuroradiology of Brain Tumors. Neurologic Clinics
1995; 13:739-740.
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