Neuroradiology Case of the Week

Case 41

Francisco Garcia-Morales, MD and P-L Westesson, MD, PhD, DDS

Clinical Presentation: A 66-year-old female with a history of breast cancer presented with dementia and syncope. A CT scan was requested to evaluate for an intracranial abnormality.

Radiological Findings: CT scan without contrast (Fig. 1A) shows a hyperdense, large mass lesion in the right posterior fossa (arrows) with enhancement after the administration of contrast (Fig. 1B). The fourth ventricle is displaced and compressed by the mass (arrow).
   Images at higher level (Fig. 2) demonstrate the mass lesion and prominent ventricles with transependymal CSF leak (arrowheads).
   T2-weighted MR image (Fig. 3) demonstrates the mass lesion to be isointense with brain tissue. On a contrast enhanced coronal T1-weighted image there is intense contrast enhancement (Fig. 4). Sagittal MR image (Fig. 5) demonstrates a mass lesion in the posterior fossa and there is marked compression of the 4th ventricle and with tonsilar herniation. The tips of the cerebellar tonsils are at the lower third of C1 (arrow).

Figure 1: CT scan without contrast (A) shows a hyperdense large mass lesion in the right posterior fossa (arrows) with significant enhancement after the administration of contrast (B).
Figure 2: CT scan higher up demonstrates the mass and prominent ventricles with presumed transependymal CSF leak (arrows).	Figure 3: MR T2-weighted image shows the mass lesion to be essentially isointense with brain tissue.
	Figure 5: Sagittal MR image demonstrates a mass lesion in the posterior fossa and there is marked compression of the 4th ventricle with tonsilar herniation (arrows).
Figure 4: Coronal MR T1-weighted image after Gadolinium demonstrates homogeneous intense contrast enhancement.

Diagnosis: Meningioma

Discussion:  Meningiomas are the most common intracranial extra-axial neoplasm [1]. They demonstrate a dual peak incidence with the first peak around 40 years and the second peak around 60 years [2]. Meningiomas are typically supratentorial with a parasagittal being the most common ones. Other locations are along the convexity, along the sphenoid ridge, olfactory groove, and parasellar regions.

Differential Diagnosis:  This case is relatively characteristic for meningioma, but breast cancer metastases could have a similar appearance. Metastases however, usually cause more edema. Hemangiopericytoma is a variant of meningiomas with usually a much more prominent vascular supply and often flow voids.
   The natural history of meningioma is a slow-growing tumor, compressing but not invading adjacent structures. Treatment consists of resection complete or partial. Stereotactic radiosurgery is another treatment modality for those meningiomas that does not lend themselves for surgery.
   The meningiomas are typically broad-based with a large dural surface contact. Many times hyperostosis seen on CT scan can give a clue to the diagnosis. On MR spectroscopy the cholin/creatinine ratio can be elevated indicating a proliferative potential of a meningioma [3]. Metastases from meningiomas are rare but both benign and so-called malignant meningiomas can metastasize [2].

References:

1. Buetow MP, Burton PC: Typical, Atypical and misleading features in meningioma. RadioGraphics 11:1087-1100, 1991.
2. Osborn, AG. Diagnostic Neuroradiology. Mosby, St. Louis, 1994, p587-602.
3. Osborn, AG. Brain - Top 100 Diagnoses.WB Saunders, 2002. p150.