Neuroradiology Case of the Week

Case 4

Ben Bedford, Manoj Ketkar, MD and P-L Westesson, MD, PhD, DDS

Clinical Presentation: A 51-year-old, right-handed, woman with a history of seizures since childhood, that have been well controlled with depakote, presented with new types of seizures and headaches over the past 9 months.

Radiological Findings: A sagittal T1-weighted MRI of the brain revealed a 2 x 3cm mass that is isointense to the cerebral cortex and adjacent to the falx cerebri in the right frontal lobe. A coronal post-contrast image of the brain shows enhancement of the mass, especially in the center. This mass is located in the proximity of the superior sagittal sinus, probably compressing it. There is minimal surrounding vasogenic edema.

Figure 1: A sagittal T1 weighted image revealed an isointense to hypointense mass (arrows) in the parasagittal location.
Figure 2: An axial T2 weighted image revealed the mass (arrows) to be iso to hypointense to the cortex.	Figure 3: Coronal post-gadolinium scan revealed intense enhancement of the mass (arrow), predominantly in the center of the mass. Note the close proximity of the mass adjacent to the superior sagittal sinus, which is compressed but not invaded by the mass.

Diagnosis: Meningioma

Discussion: Meningiomas are the most common non-glial brain tumors with an incidence of 2-3 per 100,000 [4]. The highest incidence is in women 40-60 years old [2]. Since only 10% of meningiomas cause symptoms, many are discovered incidentally on imaging studies or at autopsy. They are slow-growing, extraaxial tumors that are usually benign and arise from the meningothelial cells of the arachnoid [3]. Most meningiomas are homogeneous masses with sharply defined margins, although calcifications (whorled, sand-like deposits known as psammoma bodies) are seen in 15-20% of cases [3]. They can be found along the external surface of the brain or in the ventricles. The most common location for a meningioma is along the superior sagittal sinus, but one can also arise along the sphenoidal ridge, olfactory groove, falx cerebri, or tentorium [3]. Meningiomas usually present as solitary masses, and multiple tumors would raise the suspicion of neurofibromatosis type 2 [2]. Progesterone, estrogen, and androgen receptors exist on a subset of meningiomas and could be a potential target for treatment [1].
    The radiographic assessment of a meningioma is best done with MRI [3]. These tumors are typically isointense to gray matter on T1-weighted MRI and often hypointense on T2-weighted MRI [1]. Meningiomas can occasionally be appreciated on plain skull films by the visualization of bone erosion, calcification, or hyperostosis.
    Clinically, meningiomas produce variable symptoms based on their location in the brain. Cerebral convexity meningiomas may first be noticed by symptoms from the mass effect they induce: headache, confusion, papilledema, or focal seizures. In contrast, parasagittal or falx meningiomas may result in a progressive spastic weakness or loss of sensation on the side of the body opposite to the tumor [1].
    The treatment of meningiomas is based on their size and the symptoms of the patient. If the patient is elderly or asymptomatic, or the tumor is small, treatment may be deferred [1]. Large or symptomatic meningiomas are removed surgically as long as they are not invading vascular areas such as venous sinuses [1]. For incompletely resected meningiomas, radiation therapy has been shown to reduce the recurrence rate and prolong the time to recurrence. For smaller mengiomas stereotactic radiosurgery representa aviable treatment option. The potential efficacy of an antiprogesterone agent used to treat meningiomas is currently being studied [1].

References:

1. Abeloff: Clinical Oncology, 2nd Ed., Churchill Livingstone, Inc. 2000. pp. 1166-69.
2. Cotran, Ramzi S.: Robbins Pathologic Basis of Disease, 6th Ed., W.B. Saunders Company, 1999. pp. 1350-1351.
3. Juhl: Paul and Juhl’s Essentials of Radiologic Imaging, 7th Ed., Lippincott, Williams, and Wilkins, 1998. pp. 388-390.
4. Osborn, Anne G.: Diagnostic Neuroradiology, Mosby, 1994. pp. 584-601.