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Neuroradiology Case of the Week
Case 411
May 2009
Gurshawn Singh, MS2, and Rajiv Mangla, MD
Clinical
Presentation: Patient is a 73-year-old female with double vision.
Imaging Findings: CT images show sclerosis in the basisphenoid bone in the skull base. This appears on MR as a hypointense lesion on T1 and isointense on T2 with small soft-tissue components showing intense enhancement on T1 post-gadolinium images. This enhancement extends in bilateral cavernous sinus region along the tentorium in pre-pontine cistern in a sheet-like fashion.
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Figures 1A&B: CT axial images show sclerosis of base of skull in the region of the sphenoid bone.
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Figure 2: Axial T2 image shows isointense lesion at the skull base extending in bilateral cavernous sinuses.
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Figure 3: Post-contrast axial image show sheet-like enhancement along the dura in the region of bilateral cavernous sinuses and pre-pontine cistern.
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Figure 4: Coronal image shows enhancement along the basisphenoid bone involving the bilateral cavernous sinuses.
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Diagnosis: En plaque meningioma
Discussion: Meningiomas are the most common non-glial primary tumors accounting for 13-26% of all intracranial tumors. Most meningiomas appear as hemispheric or globular, grow inward toward the brain as well-defined dural masses. They may invade bone and induce hyperostosis while at levels slightly over the dura mater. Meningiomas which present as a flat tumor infiltrating dura and growing as a sheet along the dura or falx are referred to as en plaque meningiomas. These tumors will spread via foramina, fissures, and perforating blood vessels.
The diagnosis of en plaque meningiomas is difficult because it is not easily visualized on pre-operative studies. Hyperostosis is one of the hallmarks of the disease but is only present in 44% of the cases and can be associated with other conditions. Abnormal dural thickening and enhancement are also very suggestive of en plaque meningiomas however other diseases like sarcoid, bacterial infection, granulomatous infection, lymphoma, glioma, and meningeal carcinomatosis also present with these characteristics. The presence of dural enhancement is due to the presence of tumor and chronic inflammatory processes.
CT is useful in seeing the hyperostosis of the skull. Hyperostosis is due to the meningioma directly innervating the bone but represents reactive changes in other cases. CT is also useful to show characteristics like tumor calcification, hemorrhage, and edema. MRI has a better soft-tissue resolution and multiplanar capabilities so is the investigation of choice for meningioma imaging. These are iso to hypointense on T1, and iso to hyperintense on T2. They usually show strong homogenous enhancement but cystic and heavily calcified meningiomas can also be occasionally seen. Approximately 72% of all meningiomas will show the dural tail.
References:
- Croutch KL, Wong WH, Coufal F, Georgy B, Hesselink JR. En plaque meningioma of the basilar meninges and Meckel's cave: MR appearance. AJNR Am J Neuroradiol. 1995 Apr;16(4 Suppl):949-51. [PubMed]
- O'Leary S, Adams WM, Parrish RW, Mukonoweshuro W. Atypical imaging appearances of intracranial meningiomas. Clin Radiol. 2007 Jan;62(1):10-7. [PubMed]
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