Neuroradiolngt]

Neuroradiology (1982) 23:207-209

© Springer-Verlag 1982

CT Findings in Malignant Meningiomas* J. L. Dietemann 1, N. Heldt 2, J. L. Burguet 1, L. Medjek 1, D. Maitrot 3 and A. Wackenheim ~ Departments of 1Neuroradiology, 2pathology, and 3Neurosurgery, University Hospital, Strasbourg, France

Summary. Recurrent meningiomas are due usually to incomplete removal as in the case of basal meningiomas where the tumour surrounding vessels and nervous structures cannot be completely excised. Recurrent meningiomas of the convexity are rare after resection. In most recurrent cases histological changes are noted which may explain the rapid growth, the aggressive nature and also the malignancy of the tumour. These changes include increased mitotic activity, necrosis and invasion of the adjacent brain parenchyma. CT findings in malignant meningiomas are related to the microscopic appearance of these tumours: tumoral necrosis determines heterogeneous enhancement; brain invasion explains the irregular outline of the tumour and sometimes the absence of surrounding low attenuation area. The authors report 5 malignant meningiomas in which the CT findings are correlated with the microscopic findings. Key words: Computed tomography - Meningiomas Brain, neoplasms

Recurrence of intracranial meningiomas occurs in 10-21% of cases. The rate of recurrence is higher in basal meningiomas and in most is usually related to incomplete resection. Histological malignancy is seldom noticed in these cases. Numerous papers have been devoted to the malignant meningiomas [1, 2, 5, 7, 9, 11] but only a few deal with their CT appearance [4, 6, 8, 10, 12]. Microscopic changes may explain the CT findings: in numerous cases malignancy may be suspected on pre-operative CT scans. * Presented in part at the 17th Annual Meeting of the German Society of Neuroradiology, Ttibingen, 8-10 October 1981.

Material and Methods

Between 1976 and 1981, 5 of our patients were operated on for malignant meningioma. Four had a recurrence; 1 died a few weeks after resecting the recurrent tumour. The malignancy and the aggressive nature of meningiomas are characterized by increased mitotic activity, extensive necrosis and by invasion of the brain parenchyma [1, 2, 5, 7, 9, 11, 12]. In Table 1 the clinical and pathological data are correlated with the CT scan findings.

Results (Table 1)

We observed 3 syncytial, 1 transitional and 1 fibroblastic meningioma. In all 5 cases the pathological study revealed increased mitotic activity; in 4 cases necrotic areas were present: in all 5 invasion of the brain parenchyma was observed. Four patients had recurrences 2 years after removal. CT findings after enhancement were as follows: heterogeneous enhancement in 4 with small areas without enhancement within the tumour; irregular outline was present in all 5 cases. Low attenuation in the surrounding brain tissue was observed in 3 patients only.

Discussion

It is not always possible to correlate the aggressive nature or malignancy of meningiomas with the histological type (syncytial, fibroblastic, transitional...). Only the angioblastic and papillary types are known to behave more aggressive than the average [1, 2, 11, 12]. However the presence of increased mitotic activity, small necrotic areas, and invasion of the brain paren0028-3940/82/0023/0207/$01.00

208 Table 1. CT and pathological findings in five cases of malignant meningioma Case

Age/ Sex

Location

First removal

Recurrence

CT features Attenuation

Enhancement

+

syncytial meningioma with necrotic areas, brain parenchyma invasion, increased mitotic activity

+

transitional meningioma with small necrotic areas, extensive brain parenchyma invasion, increased mitotic activity

no peripheral low attenuation area

+

syncytial meningioma with large necrotic and hemorrhagic areas, increased mitotic activity and extensive brain parenchyma invasion

homogene- low attenuous enation ring hancement with irregular outline

+

fibroblastic meningioma with increased mitotic activity, parenchyma invasion, no necrotic areas

frontotemporal conxity.

1977 (B 27750/77)

1979 hyperdense homogene(B 9897/79) with calcifi- ous 1980 cations (B 12575/80)

2

50 m

frontal falx

1977 (B 19386/77)

1979 (B 858/79 and 946/79)

3

70 m

sphenoidal ridge

1977 (B 23730/77)

1980 hyperdense heterogene(B 4450/80) ous autopsy enhancement 1980 (A 133/80) 1981 isodense (B 9698/81)

50 f

parietal convexity

1978 (B 18793/78)

5

70 f

olfactory groove

1979 no (B 2287/79) recurrence

isodense

Peripheral area syncytial meningioma with small hemorrhagic areas, necrotic areas, brain parenchyma invasion, marked mitotic activity

68 m

4

Pathology

+

1

isodense

Isotope scan

low attenuation

irregular irregular heterogene- low area ous

heterogeneous enhancement with small low attenuation areas

no

peripheral low attenuation area

Fig.1. Malignant parietal convexity meningioma. Contrast-enhanced CT scan. Heterogeneous enhancement. Absence of surrounding edema

Fig.2. Malignant sphenoidal-ridge meningioma. Contrast-enhanced CT scan. Irregular outlines of the tumour. Absence of surrounding edema

chyma may lead to the diagnosis of malignancy. The CT features are directly related to the 2 latter microscopic findings. The necrotic areas explain the absence of enhancement in these regions and are responsible for the heterogeneous appearance of the enhanced CT scans (Fig. 1). Invasion of the brain parenchyma explains the irregular outline of the malignant meningiomas [4, 12].

Smith et al. (1981) demonstrated the absence of any relationship between the histological groups of the meningiomas and the occurence of cerebral edema. They observed that the larger meningiomas which produced cerebral edema, were the less aggressive histologically. These authors believe that the size of the tumour explains the cerebral edema [10]. Vassilouthis and Ambrose on the other hand (1979) ob-

209

Fig. 3. Autopsy specimen (A 133/80); (same patient as in Fig. 2). The residual tumour (1) invades the temporal brain parenehyma (arrows). Absence of surrounding edema

served marked or moderate brain edema around 15 of their 16 aggressive meningiomas. Only 1 patient with an angioblastic cystic meningioma did not present edema [12]. In our observations peripheral edema was absent in 2 patients (Figs. 1 and 2); 1 of these had a particularly malignant meningioma with extensive invasion of the brain parenchyma (Fig. 3). We therefore believe that the absence of peripheral edema may be related to the invasion of the brain parenchyma in the most aggressive meningiomas. We considered as did Vassilouthis and Ambrose [12] that a malignant meningioma may be suspected by the following CT findings: Moderate and heterogeneous contrast enhancement with or without cystic components. Irregular outline of the tumour. Absence of surrounding edema.

References 1. Burger PC, Vogel FS (1976) Surgical pathology of the nervous system and its coverings. Wiley and Sons, New York 2. Crompton MR, Gautier-Smith PC (1970) The prediction of recurrence in meningiomas. J Neurol Neurosurg Psychiatry 33: 80-87 3. Henry JM, Schwartz FT, Sartawi MA, Fox JL (1974) Cystic meningiomas simulating astrocytomas. Report of three cases. J Neurosurg 40:647 650

4. Kazner W, Wende S, Grumme T, Lanksch W, Stochdorph O (1981) Computertomographie intrakranieller Tumoren aus klinischer Sicht. Springer, Berlin Heidelberg New-York 5. Lee KF, Lin SR, Whiteley WH, Tsai FY, Thompson NL, Sub JH (1976) Angiographic findings in recurrent meningioma. Radiology 119:131-139 6. Russell EJ, George AE, Kricheff II, Budzilovich G (1980) Atypical computed tomographic features of intracranial meningioma. Radiology 135:6734582 7. Sch~ifer ER (1965) Rezidivh~iufigkeitbei Meningeomen. Verlaufsbeobachtungen fiber 20 Jahre. Acta Neurochir 13: 186-195 8. Sigel RM, Messina AV (1976) CT: the anatomical basis of the diminished density surrounding meningiomas. AJR 127: 139-144 9. Simpson D (1957) The recurrence of intracranial meningiomas after surgical treatment. J Neurol Neurosurg Psychiatry 20: 22-39 10. Smith HP, Cahha VR, Moody DM, Kelly DL Jr (1981) Biological features of meningiomas that determine the production of cerebral edema. Neurosurgery 8:428433 11. Tytus JS, Lasersohn JT, Reifel E (1967) The problem of malignancy in meningiomas. J Neurosurg 27:551 557 12. Vassilouthis J, Ambrose J (1979) CT scanning appearances of intracranial meningiomas. An attempt to predict the histological features. J Neurosurg 50:320-327 Received: 14 May 1982 Dr. J. L. Dietemann Service de Radiologie I Unit6 de Neuroradiologie Pavillon Clovis Vincent F-67091 Strasbourg Cedex France