Case History

A 65-year-old woman presented with personality changes, paranoia, and confusion over the course of several months. On exam, she had mild bilateral papilledema and weakness of her legs.

Diagnosis: Meningiomas

Images 4.17A–4.17D: Axial CT (4.17A), FLAIR (4.17B), and axial (4.17C) and coronal T1-weighted images (4.17D) post-Gd demonstrate a calcified extraaxial mass in the interhemispheric fissure, which is isointense to gray matter and demonstrates near homogeneous enhancement, consistent with a meningioma.

Introduction

  Meningiomas are slow-growing, generally benign tumors that comprise 20% of all primary CNS neoplasms. They are the most common benign, extraaxial, intracranial neoplasm and are second only to gliomas in frequency.

  They are believed to arise from cells of the arachnoid and they are firmly adherent to the dura. Only rarely do they invade the brain and surrounding bone.

  They occur most commonly in middle-aged women; multiple meningiomas may occur in patients with neurofibromatosis II. Prior irradiation, often for other cancers, is the only known environmental risk factor.

Clinical Presentation

  They are extraaxial tumors that produce symptoms by compressing nervous tissue externally. They can present with headaches, seizures, and focal neurological findings depending on the location of the tumor.

  Although the vast majority are benign, even grade I meningiomas sometimes invade blood vessels and may metastasize, most commonly to the lungs.

Radiographic Appearance and Diagnosis

  On CT, they are hyperdense to the brain. They are highly calcified about 25% of the time. Edema is common and is hypodense on CT.

  Meningiomas only very rarely invade the brain, but often invade and remodel the skull. This remodeling or secondary excessive growth of bone is termed hyperostosis. This is best seen with CT scans. Some meningiomas are associated with cyst formation.

  On MRI, they are typically isointense to the brain T1-weighted image and isointense or hyperintense on T2-weighted image. They may be associated with significant amounts of edema, and this is sometimes, though not always, an indicator of a more aggressive tumor. They enhance avidly and homogeneously with the administration of contrast. A characteristic enhancement appearance is the “sunburst” or “spoke wheel” pattern of vasculature created by arterial feeders that radiate into the center of the tumor.

Images 4.17E–4.17G: Postcontrast axial, sagittal, and coronal T1-weighted images demonstrate a meningioma arising from the cerebral convexity on the left with mass effect. Image 4.17H: Axial FLAIR image demonstrates peritumoral edema.

Images 4.17I–4.17K: Axial and coronal T2-weighted and postcontrast T1-weighted images demonstrate a large meningioma arising from the sphenoid wing with significant mass effect on the left temporal lobe and lateral ventricle. Image 4.17L: Gross pathology of a sphenoid wing meningioma.

Images 4.17M–4.17O: Postcontrast sagittal, axial, and coronal T1-weighted images demonstrate a homogeneous enhancing mass in the suprasellar region.

Images 4.17P and 4.17Q: Postcontrast axial and sagittal T1-weighted images demonstrate a uniformly enhancing meningioma arising from the planum sphenoidale.

Images 4.17R and 4.17S: Postcontrast axial and sagittal T1-weighted images demonstrate a uniformly enhancing meningioma in the cerebellopontine angle.

Images 4.17T–4.17V: Postcontrast axial, coronal, and sagittal T1-weighted images demonstrate a meningioma arising from the incisure of the tentorium cerebelli with downward mass effect on the cerebellum.

Images 4.17W and 4.17X: Postcontrast axial and sagittal T1-weighted images demonstrate an enhancing mass in the fourth ventricle with significant mass effect on the lower brainstem and cerebellum.

Images 4.17Y and 4.17Z: Postcontrast axial T1-weighted and FLAIR images demonstrate an enhancing mass in the occipital horn of the lateral ventricle and falx cerebri over the occipital lobe. There is mass effect and edema. An additional mass is seen arising from the posteior falx cerebri.

Images 4.17AA and 4.17BB: Postcontrast axial and sagittal T1-weighted images demonstrate a well-circumscribed, extramedullar meningioma (red arrows) with compression of the spinal cord (yellow arrow).

Images 4.17CC and 4.17DD: Postcontrast axial and coronal T1-weighted images demonstrate a well-demarcated enhancing mass superiorly located at the left orbital apex (yellow arrows). The superior rectus muscle is displaced inferiorly and medially as is the optic nerve (red arrow). These tumors may be difficult to differentiate from optic nerve gliomas.

Images 4.17EE–4.17GG: Axial, sagittal, and coronal CT images demonstrate a hyperdense meningioma arising from the planum sphenoidale. Image 4.17HH: Axial CT image from a different patient scan shows a heavily calcified meningioma arising from the left sphenoid wing.

Images 4.17II and 4.17JJ: Axial FLAIR and postcontrast T1-weighted images demonstrate a left subfrontal meningioma with surrounding edema. Images 4.17KK and 4.17LL: Axial and coronal CT images demonstrate hyperostosis (red arrows) of the bone in a patient with a meningioma.

Images 4.17MM–4.17PP: Axial FLAIR, T2-weighted, and pre- and postcontrast T1-weighted images demonstrate the characteristic findings of a meningioma. It is hyperintense on T2-weighted images with edema. It is isointense on T1-weighted images with “sunburst” or “spoke wheel” enhancement on postcontrast images.

  A characteristic finding is known as a dural tail. This refers to enhancement of the meninges flanking the bulk of the tumor, though this finding is seen in other neoplasms as well.

  In contrast to lower grade meningiomas, more aggressive tumors may display a heterogeneous pattern of enhancement and significant peritumoral edema, though such edema may occur with benign subtypes as well. They may invade the bone and the underlying brain.

  Meningiomas are highly vascular tumors and cerebral angiograms are often performed prior to an operation to better define the vasculature surrounding the meningioma. On angiograms the tumor blush is seen in the arterial phase and remains in the venous phase. Since the finding comes early and stays late, this is called the “mother-in-law” sign.

  Pathologically, meningiomas occur in several types including meningothelial (meningeal cells with indistinct cell borders arranged in whorls), angiomatous, microcystic, and fibrous. These patterns do not correlate with an aggressive phenotype and are generally seen in WHO grade I meningiomas.

Images 4.17QQ and 4.17RR: Postcontrast axial T1-weighted images demonstrate homogeneously enhancing extraaxial masses in the left cerebellopontine angle and along the right cerebral convexity. In both cases, a characteristic dural tail is seen (red arrows).

Images 4.17SS–4.17VV: Postcontrast axial and sagittal T1-weighted and axial FLAIR images demonstrate a right frontal convexity meningioma with extensive bony invasion and associated calvarial expansion. The margins of the meningioma with the frontal lobe brain tissue are ill-defined suggesting brain invasion.

Images 4.17WW and 4.17XX: Catheter angiography reveals tumor blush (red arrows), in both the arterial and venous phases, the “mother-in-law” sign. Inset, an axial postcontrast T1-weighted image shows a large falx meningioma.

Image 4.17YY: H&E stain showing meningothelial, microcystic, and fibrous meningiomas (image courtesy of Dr. Seema Shroff, Fellow, Neuropathology, NYULMC).

Image 4.17ZZ: Immunostains for epithelial membrane antigen and progesterone receptors (image courtesy of Dr. Seema Shroff, Fellow, Neuropathology, NYULMC).

  Meningioma cells are immunoreactive for epithelial membrane antigen and progesterone receptors.

  Chordoid and clear-cell meningiomas have a higher rate of recurrence and are classified as WHO grade II. Rhabdoid and papillary meningiomas are aggressive neoplasms that warrant WHO grade III.

  Meningiomas with a mitotic count greater than 4/10 high power fields are classified as atypical (WHO grade II) and those with more than 20/10 high power fields are classified as anaplastic (WHO grade III).

  WHO grade I meningiomas have a pushing border against the brain; however, meningiomas with brain invasion have a higher rate of recurrence, warranting classification as WHO grade II.

Image 4.17AAA: H&E stain demonstrating chordoid and rhabdoid meningiomas (image courtesy of Dr. Seema Shroff, Fellow, Neuropathology, NYULMC).

Image 4.17BBB: H&E staining of a meningioma showing multiple mitotic figures (yellow ovals) (image courtesy of Dr. Seema Shroff, Fellow, Neuropathology, NYULMC).

Image 4.17CCC: H&E staining of a meningioma showing brain invasion (red arrows) (image courtesy of Dr. Seema Shroff, Fellow, Neuropathology, NYULMC).

Treatment

  Surgical resection is the mainstay of treatment for meningiomas. Larger tumors may require preoperative embolization of the tumor. Up to 25% recur, and the recurrence rate for more malignant tumors is much higher, up to 80%, and radiation may be used for such tumors. SRS is particularly useful for tumors where surgical removal of the tumor is difficult, such as the cavernous sinus. Atypical and malignant meningiomas are associated with an increased risk of local recurrence and decreased overall survival compared with grade I meningiomas. Asymptomatic meningiomas may be followed with repeat imaging. For patients with atypical meningioma, close surveillance serial MRIs are obtained at 3, 6, and 12 months postoperatively, then every 6 to 12 months for 5 years, and then every 1 to 3 years.

References

1.  Stessin AM, Schwartz A, Judanin G, et al. Does adjuvant external-beam radiotherapy improve outcomes for nonbenign meningiomas? A Surveillance, Epidemiology, and End Results (SEER)-based analysis. J Neurosurg. 2012;117:669.

2.  Perry A, Louis DN, Scheithauer BW, et al. Meningiomas. In: Louis DN, Ohgaki H, Wiestler OD, eds. WHO Classification of Tumours of the Central Nervous System. Lyon: IARC Press; 2007:164.

3.  Longstreth WT, Dennis LK, McGuire VM, et al. Epidemiology of intracranial meningiomas. Cancer. 1993;72:639–648.

4.  Hsu DW, Efird JT, Hedley-Whyte ET. Progesterone and estrogen receptors in meningiomas: prognostic considerations. J Neurosurg. 1997;86:113–120.