Clinical
Presentation: Patient is a 72-year-old female with dementia.
Imaging Findings: Non-contrast CT images show a well-defined calcified lesion, 15x17mm in size in the floor of anterior cranial fossa in midline. The lesion is extraaxial, dural based, shows isointense signal on T1, slightly hypointense signal on T2, and strong enhancement in post-contrast images. There is enhancement of the dura adjacent to the lesion. Pituitary gland is seen separately from the lesion and appears normal.
Figure 1: Non-contrast CT image shows a calcified lesion in the floor of anterior cranial fossa.
Figures 2A-B: The lesion is seen to have isointense signal to the cortex in T1W images and slightly hypointense signal in T2W images.
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Figure 3A-B: Post-contrast T1W images show strong enhancement of the lesion. Dural tail is seen adjacent to the lesion. Pituitary gland appears normal.
Diagnosis: Calcified meningioma
Discussion: Five to 10% of meningiomas are seen in the parasellar location and can arise from planum sphenoidale, diaphragma, tuberculum, or dorsum sellae [1, 2]. These are not usually centered on the sella turcica. Meningiomas in this location can be confused with other supra/para sellar lesions like pituitary macroadenomas, craniopharyngiomas, aneurysms, or those arising from the sphenoid bone.
Hyperostosis, irregular cortex, tumoral calcifications, and prominent vascular markings may be seen in the skull radiographs. In the non-contrast CT scans, meningiomas are seen as sharply circumscribed smooth masses abutting the dura. Seventy to 75% of meningiomas appear hyperdense and calcification can be seen in 20 to 25% [1]. Dense homogeneous enhancement is characteristic of meningioma and because this is uncommon in other perisellar neoplasms, this feature provides some histologic specificity for meningioma.
In T1W images, most of the meningiomas are nearly isointense to the cortex (56 - 94%). About half of the meningiomas (43 - 52%) are isointense in T2W images and about 35 to 44% are hyperintense. Hypointense lesions in T2W images are less common (4 - 18%). The signal intensity in T2 has been correlated to the histologic type of the meningioma. Fibroblastic variants were iso to hypointense, angioblastic and syncytial types were mainly hyperintense while transitional meningiomas were iso to hyperintense [3].
Gray matter buckling due to extraaxial location is seen better with T1W images, while CSF clefts and flow voids are better seen with T2W images. Strong and homogeneous enhancement is usually seen. Meningiomas usually form obtuse margins with the underlying calvarium [2]. Meningeal enhancement or the dural tail sign is commonly associated with meningiomas, but is not specific as it can be seen with other intracranial tumors due to dural reaction. MRS can show elevated levels of alanine at short TE, with reported peak ranging from 1.3 to 1.5 ppm [1].
Flow voids or prominent angiographic tumoral vascularity is a common feature of meningiomas. MR flow voids or MR angiography flow signal may also be caused by normal encased vessels. If flow voids or abnormal vessels have the characteristic broom like or sunburst morphology, then meningioma should be suspected [2]. Uniform angiographic tumoral opacification or tumor blush, with prolonged staining is a common feature of meningiomas.
References:
Osborn A, Salzman K, Barkovich, AJ, et al. Saccular aneurysms IN: Diagnostic Imaging, Brain. 2nd ed., Lippincott Williams & Wilkins, 2009:I-3, 12-15.
Donovan JL, Nesbit GM. Distinction of masses involving the sella and suprasellar space: specificity of imaging features. AJR Am J Roentgenol. 1996 Sep;167(3):597-603. PMID: 8751659 [PubMed]
Maiuri F, Iaconetta G, de Divitiis O, Cirillo S, Di Salle FD, De Caro ML. Intracranial meningiomas: correlations between MR imaging and histology. Eur J Radiol. 1999 Jul;31(1):69-75. PMID: 10477102 [PubMed]
