Intracranial meningiomas: how frequent are indicative findings in CT and MRI?

External beam radiation therapy for meningioma

Radiation therapy (RT) plays an important role in the management of meningioma. Surgery often remains the initial treatment of choice as it reduces mass effect and confirms the diagnosis and grade. However, RT has frequently been successful in the primary setting and is commonly employed as adjuvant therapy for incompletely resected tumors as well as for high-grade meningiomas regardless of resection extent. Some meningiomas develop in locations less amenable to resection or in patients who are poor surgical candidates, in which circumstances RT is particularly appropriate as primary treatment. Recent cooperative group studies including RTOG 0539 have better established the role of RT for meningioma. These studies suggest a role for adjuvant RT for completely resected Grade II meningioma, which was less clear historically. Ongoing clinical trials such as NRG BN 003 and ROAM will further clarify this. This chapter reviews the role of fractionated external beam RT for various grades of meningioma.

Incidental Meningiomas: Management in the Neuroimaging Era

The number of patient imaging studies has increased because of precautious physicians ordering scans when a vague symptom is presented; subsequently, the number of incidental meningiomas detected has increased as well. These brain tumors do not present with related symptoms and are usually small. MRI and computed tomographic scans most frequently capture incidental meningiomas. Incidental meningiomas are managed with observation, radiation, and surgical resection. Ultimately, a conservative approach is recommended, such as observing an incidental meningioma and then only radiating if the tumor displays growth, whereas a surgical approach is to be used only when proven necessary.

Lesions masquerading as acute stroke

Rapid and accurate recognition of lesions masquerading as acute stroke is important. Any incorrect or delayed diagnosis of stroke mimics will not only increase the risk of being exposed to unnecessary and possibly dangerous interventional therapies, but will also delay proper treatment. In this article, written from a neuroradiologist's perspective, we classified these lesions masquerading as acute stroke into three groups: lesions that may have "normal imaging," lesions that are "symptom mimics" but on imaging clearly not a stroke, and lesions that are "symptom and imaging mimics" with imaging findings similar to stroke. We focused the review on neuroimaging findings of the latter two groups ending with a suggestion for a diagnostic approach in the form of an algorithm.

Intracranial meningiomas of atypical (WHO grade II) histology

Atypical (WHO grade II) meningiomas occupy an intermediate risk group between benign (WHO grade I) and anaplastic (WHO grade III) meningiomas. Although grade II meningiomas have traditionally been recognized in only about 5% of cases, after changes in diagnostic criteria with the current 2007 WHO standards, they now comprise approximately 20-35% of all meningiomas. Given the magnitude of this change, much work is now needed to solidify the adoption of these standards, to render inter-observer and inter-institutional comparisons more uniform, and to more carefully define the incidence of grade II histology. However, it is clear that they carry a several-fold increased risk of recurrence, as well as an increased rate of mortality. We will discuss the definition, diagnosis, and treatment of patients with atypical meningioma; review the current phase II cooperative trials; and draw attention to some questions timely for pre-clinical and clinical research.

Magnetic resonance imaging and diffusion-weighted images of cystic meningioma

BACKGROUND AND PURPOSE

Cystic meningiomas are quite rare, accounting for between 2% and 4% of all intracranial meningiomas. To better understand all the types of cystic meningiomas with magnetic resonance imaging (MRI), diffusion-weighted imaging (DWI) and histopathology, we attempted to correlate the MRI and DWI features of cystic meningiomas with the histopathological findings.

METHODS

We collected 15 cases of cystic meningiomas diagnosed between 1993 and 2000 (5 men and 10 women, 41-80 years old). Fifteen patients had conventional MRI and 14 patients had CT scan. DWI was also performed in three patients. Apparent diffusion coefficient (ADC) images were also done. In the classification of cystic meningiomas, we adopted Worthington's classification, which divides cystic meningiomas into five groups.

RESULTS

Tumor resection was performed in all patients. Tumor locations were as follows: convexity (10), falx (2), pterion (2) and lateral ventricle (1). Regarding the types of cystic lesion, type I (3), type II (3), type III (3), type IV (1) and type V (5) were found. Histopathologically, there were six atypical, four meningothelial, two malignant, one fibroblastic, one angiomatous and one transitional. Intratumoral cystic meningiomas were more common in atypical types. Peritumoral cystic meningiomas were more common in meningothelial and atypical types. The cystic portion of the three cystic meningiomas was hypointense or mildly hyperintense on DWI. ADC ratio (ADCR) of DWI for cyst part of two type I cystic meningiomas was 1.25 and 0.82; for cyst part of one type III was 4.04.

CONCLUSIONS

It is important to recognize the neuroimaging features of the cystic meningiomas. Conventional MRI and DWI may play an important role in the preoperative radiological evaluation and the recognition of these types of cysts for proper surgical treatment.

Primary ectopic meningioma in the right ethmoid sinus: a case report

A 29-year-old female with primary ectopic meningioma in the right ethmoid sinus was reported. She was treated by a right lateral rhinotomy with total removal of the tumor and the subsequent clinical course was good. Contrast enhanced magnetic resonance image (MRI) was most informative to define the tumor and decide the surgical procedure, in which it was demonstrated as well circumscribed mass lesion with considerable homogeneous contrast enhancement.

MRI in the diagnosis of cystic meningiomas: surgical implications

Nine cases of cystic meningioma diagnosed by MRI are described. All cases were surgically confirmed. The lesion was extra-axial with a clear dural attachment. On T1-weighted images the solid component was iso-hypo-intense in 6 cases and iso-hyperintense in 3; on T2-weighted images it was hyperintense in 7 cases, iso-intense in 2. After i.v. injection of gadolinium, the solid component enhanced in all cases and a "dural tail" were visible in 8 cases. No gadolinium enhancement of the cyst wall was observed in Nauta's types II and III. The authors found MRI to be very useful for diagnosis of cystic meningioma but insufficient for differential diagnosis between types II and III according to Nauta. This aspect requires further study, especially in view of the implications of this differentiation in terms of surgical management.

Management of posterior cranial fossa meningiomas

Posterior cranial fossa meningiomas are relatively common extra-axial tumors with important relationships to the cochleovestibular system, facial nerve, and/or cranial base. Nevertheless, objective reporting of auditory and vestibular function is rare for this patient population, and a full discussion of the nonsurgical management is all but totally discounted in the otolaryngology literature. Nine cases (8 operative cases) are presented, with the purpose of correlating neurotologic function with precise anatomic tumor location, available by magnetic resonance imaging and computed tomography. The usefulness of this information for diagnosis and meaningful scrutiny of the operative results is discussed. A comprehensive review of posterior fossa meningiomas in terms of epidemiology, etiology, and pathology, as well as nonsurgical treatment alternatives, is provided.

Preoperative differentiation between meningioma of the cerebellopontine angle and acoustic neuroma using MRI

Preoperative differentiation between acoustic neuroma (AN) and meningioma of the cerebellopontine angle (CPA) is important in selection of the surgical approach, successful tumor removal, and preservation of hearing and facial nerve. We retrospectively reviewed the magnetic resonance imaging (MRI) findings associated with 30 meningiomas involving the CPA (MCPA) encountered between 1987 to 1991 at the University of California, San Francisco. Magnetic resonance imaging was critical in differentiating meningioma from AN in the CPA. Typical findings on MRI associated with MCPA, differentiating them from ANs, include: meningiomas are sessile, possessing a broad base against the petrous face, whereas ANs are globular; they are often extrinsic and eccentric to the internal auditory canal (IAC); when involving the IAC, they usually do not erode the IAC; MCPAs demonstrate hyperostosis of the subjacent bone and possess intratumoral calcification; they involve adjacent intracranial spaces and structures; and meningiomas are characterized by a distinctive dural "tail" extending away from the tumor surface. While any one finding may not be diagnostic by itself, taken together the constellation of these findings is strongly indicative of meningioma. In our experience, MRI with gadolinium enhancement was able to distinguish MCPA from AN in nearly every case.

Clinical presentation of meningioma in the elderly

OBJECTIVE

To compare presenting manifestations of meningioma in elderly patients with those in younger patients.

DESIGN

Retrospective survey.

SETTING

Tertiary care center.

PATIENTS

All hospitalized adult patients with the primary diagnosis of meningioma over a 5-year period (n = 116). Nine patients with recurrence of a previously resected meningioma were excluded. Fifty-two percent (56/107) of patients were > or = 65 years of age.

MEASUREMENTS

Presenting symptoms were classified as asymptomatic, focal, non-specific, or both focal and non-specific. Presenting neurologic signs on physical examination were classified as focal, non-focal, or normal. Duration of symptoms was classified as < or = 1 week, 1 week to 1 month, 1 to 6 months, and > 6 months.

RESULTS

Older patients presented more commonly with confusion (32% vs 4%) and dystaxia (28% vs 10%) than younger patients and presented less commonly with headache (23% vs 49%) and visual changes (21% vs 43%). While 2% of patients were asymptomatic at presentation, the remainder had symptoms categorized as focal (38%), non-specific (26%), or both (34%). There was no significant difference between older and younger age groups in the proportions of patients having focal symptoms. Duration of symptoms for all patients was categorized as < or = 1 week (15%), 1 week to 1 month (16%), 1 to 6 months (23%), and > 6 months (44%). In general, older patients were diagnosed earlier than younger patients. The presence of focal neurologic signs was not significantly different between older and younger patients.

CONCLUSIONS

Presenting manifestations of meningioma differ between older and younger adult patients, but focality of symptoms and signs is similar. In this case series, the duration of symptoms prior to diagnosis was shorter in older than in younger patients.