www.elsevier.com/locate/jocn

Journal of Clinical Neuroscience 14 (2007) 856–859

Clinical study

Cystic meninigioma

Meng Liu, Yuguang Liu *, Xingang Li, Shugan Zhu, Chengyuan Wu

Department of Neurosurgery, Qilu Hospital of Shandong University, Jinan, 250012, P.R. China

Received 25 February 2006; accepted 4 June 2006

Abstract

To study the clinical characteristics of cystic meningiomas, we analyzed retrospectively 21 patients with cystic meningiomas andreviewed the literature with regard to clinical presentation, imaging features, preoperative diagnosis, surgical findings, and histopathol-ogical results. The cysts were classified into intratumoral and peritumoral cysts based on their relationship to the tumor, and also accord-ing to the classification method described by Nauta. For the 21 patients in our group, there were seven peritumoral cysts and 14intratumoral cysts. Various pathophysiological mechanisms contribute to the formation of cystic meningiomas. The diagnosis of cysticmeningiomas based on CT scan can be problematic, and differentiation from glioma or metastasis may be difficult. MRI scans show lowsignal intensity areas within the mass on T1-weighted images and high signal intensity areas on T2-weighted images, and the solid parts oftumors are contrast-enhanced after gadolinium administration. MRI with gadolinium enhancement dramatically increases the diagnosticaccuracy for cystic meningiomas and provides critical information for their surgical care. Total surgical resection of cystic meningioma isideal, but special attention should be paid to the cyst walls.� 2006 Elsevier Ltd. All rights reserved.

Keywords: Cystic meningiomas; Intrtumoral; Peritumoral; CT; MRI

1. Introduction

Meningiomas are generally solid tumors and their clas-sical appearance on CT scan and MRI usually leads to acorrect diagnosis. A problem in diagnosis arises when men-ingiomas have cystic components that cause confusion withother tumors, including glial or metastatic tumors withcystic or necrotic changes, neuroblastoma, or hemangio-blastoma.1–4 Cysts associated with meningiomas areuncommon. The incidence may vary from 1.6–10%.1,5–9

Twenty-one patients with cystic meningioma out of a seriesof 546 meningiomas were treated in our hospital from June1992 to June 2003, with diagnoses confirmed by operationand pathology. We analyzed retrospectively these 21 pa-tients and reviewed the literature with regard to clinical

0967-5868/$ - see front matter � 2006 Elsevier Ltd. All rights reserved.

doi:10.1016/j.jocn.2006.06.003

* Corresponding author. Tel.: +86 531 82169424; fax: +86 531 88382060.

E-mail address: lygqilu@126.com (Y. Liu).

presentation, imaging features, preoperative diagnosis, sur-gical findings, and histopathological results.

2. Clinical material

In this series there were nine male and 12 female pa-tients, with an age range of 31–58 years (mean, 42.6 years).The duration of initial symptoms prior to definitive diagno-sis was 25 days to 12 years. None of the cystic meningiomashad previous radiotherapy. The presenting clinical symp-toms in patients with cystic meningiomas included head-aches, nausea, vomiting, seizures, focal neurologicaldeficits, memory loss, and personality changes. The clinicalfindings are summarized in Table 1. Nauta et al.10 classifiedcystic meningiomas into four types according to the site ofthe cavity. Rengachary et al. recognize only two kinds ofcysts: intratumoral cysts and peritumoral cysts, dependingon whether the cyst is lined by meningothelial cells.11 Weclassified our patients based on Rengachary and Nauta’smethods. Of the 21 patients in our group, there were seven

Table 1Clinical details of 21 patients with cystic meningiomas

Cyst type No. Sex Age (years) Tumor locations Histological findings

M F

Intratumoral 14 6 8 31–56 Parietal conviexity (4), frontal convexity (3),frontotemporal convexity (1), parietooccipital convexity (1),sphenoid ridge (4), petrous ridge/posterior fossa (1)

Meningothelial (6), angiomatous (4),fibroblastic (3), anaplastic (1)

Peritumoral 7 3 4 35–58 Parietal conviexity (3), frontal convexity (2), tuberculum sella(1), olfactory groove (1)

Meningothelial (5), fibroblastic (2)

M. Liu et al. / Journal of Clinical Neuroscience 14 (2007) 856–859 857

peritumoral cysts and 14 intratumoral cysts. The Nautaclassification is shown in Table 2.

There were 14 intratumoral cysts. Six were Nauta type Iand eight type II. Out of the 14 patients, six were male andeight female. Nine of the 14 patients had convexity menin-giomas. Four were attached to the lateral sphenoid wingand one to the petrous ridge in the posterior fossa. Histop-athologically, six were meningotheliomatous, four angiob-lastic, three fibroblastic, and one anaplastic.

All patients with intratumoral cystic meningiomas hadplain and contrast-enhanced CT scans; MRI scans wereperformed in 10 cases. CT scan showed mixed densitymasses, which were isodense on plain scan with hypodenseareas. On contrast enhancement, the isodense part of thetumor enhanced. In Nauta type I cystic meningiomas,MRI scans showed small low signal intensity areas withinthe mass lesions on T1-weighted images and high signalintensity areas on T2-weighted images. The solid compo-nents of the mass lesions showed isointensity, hypointen-sity, or mixed signal intensity on T1-weighted images andisointensity, hyperintensity, or mixed signal intensity onT2-weighted images. The solid parts of tumors were con-trast-enhanced after gadolinium administration. In Nautatype II cystic meningiomas, the solid components showedisointensity to hypointensity on T1-weighted images andisointensity to hyperintensity on T2-weighted images. Thecystic components showed cerebrospinal fluid signal inten-sity on both T1- and T2-weighted images. Gadoliniumenhancement was demonstrated in the solid componentsas well as in the cyst walls.

Of seven patients with peritumoral cysts, three weremale and four female. Five of the seven patients had con-vexity meningiomas. One patient had a tuberculum sellaemeningioma, whereas another had an olfactory groovemeningioma. Histopathologically, five were meningothelio-matous and two fibroblastic. CT scans were performed inall patients and MRI scans in five. Five cysts were Nautatype IV and two type III. The imaging features of this

Table 2Classification of 21 patients with cystic meningiomas

Nautatype

Description No.

I Centrally located intratumoral cyst 6II Peripherally located intratumoral cyst 8III Peritumoral cyst in the adjacent parenchyma 2IV Peritumoral cyst between the tumor and the adjacent

parenchyma5

group were similar to those of the type II group, exceptthat no enhancement of the cyst walls was demonstratedon post-contrast studies.

All patients were surgically treated. Total resection wasachieved in 19 patients and subtotal in two. One was a pet-rous ridge/posterior fossa meningioma and the other atuberculum sellae meningioma. In six cases of Nauta typeI cystic meningiomas, irregular cystic or necrotic areas werefound within the tumor mass at the time of surgery and onhistopathology. Tumor involvement of the cyst wall waspathologically seen in eight patients with Nauta type II cys-tic meningiomas. Gliotic tissue lining the cyst walls withoutany tumor cells was the main histopathological character-istic in two cases of Nauta type III cystic meningiomasand five of Nauta type IV. The patients were followed upfor 1–12 years. One patient with petrous ridge/posteriorfossa meningioma recurred and re-operation was per-formed without new morbidity.

3. Discussion

3.1. Incidence

Penfield was the first to describe cyst formation in men-ingiomas. Cushing and Eisenhardt, in their series of menin-giomas, report that cysts were present in 4.2% of patients.5

Claveria et al. found six cysts out of 71 patients with men-ingiomas,12 and Russell et al. reported six intratumoral andthree arachnoid cysts in 131 patients with meningiomas.7

The incidence may vary from 1.6% to 10%. Fortunaet al. present the largest series, in which 22 cystic meningio-mas of 1313 intracranial meningiomas (1.7%) were oper-ated on in a 35-year period.1 In our hospital, we reviewedthe intracranial meningiomas operated upon in an 11-yearperiod and found 21 cystic meningiomas out of 546 totalmeningiomas, with an incidence of 3.8%. Cystic meningio-mas are more common in the pediatric age group than inadults. They are seen in 24% of all pediatric meningiomasand in 44% of meningiomas in the 0–2-year age group.13

The incidence of cyst formation in meningiomas ininfants is higher than in childhood, adolescence oradulthood.8,14,15

3.2. Classification and etiology

Various authors have classified cystic meningiomas.Nauta et al.10 classify them into four types according to

858 M. Liu et al. / Journal of Clinical Neuroscience 14 (2007) 856–859

the site of the cavity: (i) centrally located intratumoral cyst;(ii) peripherally located intratumoral cyst; (iii) peritumoralcyst in the adjacent parenchyma; and (iv) peritumoral cystbetween the tumor and the adjacent parenchyma. Reng-achary et al. recognize only two kinds of cysts: intratu-moral cysts and peritumoral cysts.11 Worthington et al.describe five types of cystic meningiomas.16 We find theclassifications of Rengachary and Nauta more useful andclassified our patients based on their methods. In our seriesof 21 patients with cystic meningiomas, six were Nautatype I, eight type II, two type III, and five type IV.

Pathophysiological mechanisms in the formationof meningioma cysts have been discussed by variousauthors.10,11,16–18 Penfield suggested that cyst formation oc-curs secondary to central degeneration.5 Cushing statedthat xanthochromic fluid appears to form at the peripheryof the tumors where coalescence forms fairly large cavitieswith no evidence of adjacent tumor degeneration.5 The cystmay produce a mass as large as the meningioma itself. Inseveral instances, the expansion of the cyst rather than thetumor is responsible for the increased mass effect and clini-cal deterioration. According to Fortuna,1 intratumoralcysts are the outcome of: (i) microcystic degeneration; (ii)ischemic necrosis; or (iii) hemorrhage. Microcystic degener-ation is considered to be the confluence of cellular degener-ative phenomenae such as vacuolar, myxomatous, mucoid,and fatty degeneration, leading to the formation first ofmicrocavitations and then of macrocavitations within thetumor. The necrosis is frequently seen in rapidly growingtumors. Meningiomas undergoing necrosis are more oftenof the meningothelial or angioblastic type and have aslightly higher rate of atypia and postsurgical recurrence.19

Peritumoral cysts are large, generally unilocular, and con-tain xanthochromic fluid with high protein content. A perit-umoral cyst of Nauta type III may be the outcome of areactive gliosis or fibroblastic proliferation or the final stageof intense peritumoral edema.3,11 The formation of peritu-moral cysts of Nauta type IV may be secondary to a widen-ing of the subarachnoid space or mechanical trapping of thecerebrospinal fluid spaces compressed by the tumor, andless commonly, true arachnoid cysts.3 It is possible thatmore than one process may be involved in formation ofthe cyst. It has been suggested that the term ‘cystic menin-giomas’ should be limited to those lesions with a cyst insidethe tumor, with the term ‘meningioma associated with cyst’being limited to those with a satellite cyst.5,20

3.3. Radiological appearance and diagnosis

Before the advent of CT and MRI scans, necrosis and itsresidua were thought to be extremely uncommon in un-treated relatively static tumors, such as meningiomas.9

More patients with cystic or necrotic meningiomas havebeen reported since the introduction of CT and MRI scans.The most frequent location of cystic meningiomas is on thecerebral convexity; the parasagittal region is the secondmost frequent location.1,6,21 The occurrence of a cystic tu-

mor in a typical location for a meningioma may be helpfulin the diagnosis, and the recognition of a relatively broadsurface of contact with the dura is of greater value.3,9 CTscans often show mixed density masses, which are isodenseon unenhanced scan with hypodense areas. On contrastenhancement, the isodense part of the tumors is enhanced.On CT scans, peritumoral cysts may be seen as a zone ofdiminished density of variable width surrounding the tu-mor. Pathologically, this zone of hypodensity could repre-sent edema, a widened subarachnoid space, loculated CSF,demyelination, an adjacent tumor, or a peritumoralcyst.8,22 Peritumoral cysts are often larger than the main tu-mor mass and may account for the mass effect produced onthe adjacent brain.11,16 Diagnosis of cystic meningiomasbased on CT scan can be problematic. Differentiation fromglioma or metastasis may be difficult. Worthington re-ported six patients with cystic meningiomas, of whom fivereceived computed tomography,16 and a correct preopera-tive diagnosis was made for only two of the five patients(40%). Dell reported eight patients with cystic meningio-mas and found that CT scan is inadequate for accuratediagnosis, with only four lesions correctly diagnosed beforesurgery (50%).18 In a recent review of the literature, Uman-sky stated that the diagnosis was correct for 56% of the pa-tients for whom CT scans were done.21

MRI with gadolinium enhancement has dramatically in-creased the accuracy of diagnosing cystic meningiomas as aresult of a combination of factors, including an increasedsoft tissue resolution, a multiplanar imaging capability,and a lack of artifacts. For Nauta type I cystic meningio-mas, MRI scans show small low signal intensity areas with-in the mass on T1-weighted images and high signal intensityareas on T2-weighted images, and the solid parts of tumorsare contrast-enhanced after gadolinium. For Nauta type IIcases, the solid components of the cystic meningiomasshow isointensity to hypointensity on T1-weighted imagesand isointensity, hyperintensity, or mixed intensity on T2-weighted images, and the cystic components show cerebro-spinal fluid signal intensity on both T1- and T2-weightedimages. Gadolinium enhancement is demonstrated in thesolid components as well as in the cyst walls. The imagingfeatures of peritumoral cystic meningiomas are similar tothose of the type II group, except that no enhancementof the cyst walls is demonstrated on post-contrast studies.MRI with gadolinium enhancement can provide importantinformation to distinguish the cyst wall containing tumorcells (type II) from the cyst wall composed of gliotic tissuewithout any tumor infiltration (type III). MRI may show adural attachment, extra-axial location, and cerebral edemabetter than CT, and MRI demonstration of the thickeningof the dura is sometimes a useful clue to the nature of a cys-tic meningioma.3,9,23

It was difficult to diagnose cystic lesions preoperativelybefore the introduction of the CT scan. Although it is easierto recognize the cysts with modern imaging techniques, thatrecognition can give rise to diagnostic errors in differentiat-ing cystic meningiomas from other intracranial tumors. Zee

M. Liu et al. / Journal of Clinical Neuroscience 14 (2007) 856–859 859

et al. reported accurate diagnosis was made on MRI scansfor 12 out of 15 patients (80%).9 In our series of 15 patientswith cystic meningiomas who underwent MRI scans, accu-rate diagnosis was made for 11 patients (73.3%). Of the 21patients who underwent CT scans, the diagnosis of cysticmeningioma was made for nine patients (42.9%). We believeMRI with gadolinium enhancement dramatically increasesthe diagnostic accuracy of cystic meningiomas and providescritical information for their surgical care.

3.4. Treatment and prognosis

Total surgical resection of cystic meningiomas is ideal,but special attention should be paid to the cyst walls. Dif-ferent opinions about cyst wall resection have been dis-cussed. Zee et al. believe total removal of the cyst wall isindicated in type II, but not type III meningiomas. In ouropinion, a total excision of the cyst walls with tumor infil-tration is necessary to prevent a recurrence. Surgically, typeII cystic meningiomas are the most difficult to remove withthe cyst walls, and gross total removal is often difficult. Onthe other hand, type III cystic meningiomas may possiblybe treated by cyst decompression and removal of the asso-ciated solid component. However, some authors think thatthe cyst walls consist of neoplastic meningothelial cells.Ruelle et al. suggest that intratumoral cyst walls are neo-plastic and that peritumoral cyst walls contain gliotic pro-liferation.24 Rengachary et al. report that extratumoral cystwalls consist of brain parenchyma with glial cell prolifera-tion as confirmed by the presence of glial fibrillary acidicprotein.11 Umansky et al. recommend total removal ofthe tumor, including the cyst walls, because complete exci-sion of the cyst walls will minimize the incidence of recur-rence of these benign tumors.21 We believe when the solidtumor has no a capsule against the cyst, it is advisable toremove the cyst because it may contain neoplastic cells;but when the meningioma has a capsule facing the cystand its walls are lined by typical arachnoid, excision isnot necessary. Multiple biopsies and frozen sections ofthe cyst walls are helpful in deciding cyst excision.

In conclusion, cysts associated with meningiomas,though uncommon, should be considered in the differentialdiagnosis of cystic lesions. Peritumoral and intratumoralcysts form separate subtypes with distinct characteristics.There are various pathophysiological mechanisms in theformation of cystic meningiomas. MRI with gadoliniumenhancement can dramatically increase the diagnosticaccuracy for cystic meningiomas and provides criticalinformation for their surgical care. Total surgical resectionof cystic meningiomas is ideal, and special attention shouldbe paid to the cyst walls.

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