Neuro-radiology

Neuroradiology (1994) 36:289-291

9 Springer-Verlag 1994

Intracranial alveolar echinococcosis: CT and MRI A. H. Bensaid 1, J. L. Dietemann 1, M.M. Filippi de la Palavesa 1, A. Klinkert 1, B. Kastler 1, A. Gangi 1, G. Jacquet 3, F. Cattin 2 1 Department of Radiology B, University Hospital, Strasbourg, France 2 Department of Radiology, University Hospital, Besan~on, France 3 Department of Neurosurgery, University Hospital, Besan~on, France

Abstract. Intracranial alveolar echinococcosis is u n c o m mon. We r e p o r t a patient with right frontal lobe and palpebral lesions s e c o n d a r y to a p r i m a r y hepatic focus with secondary lesion in the lung. T h e intracranial and p a l p e b r a l cystic masses were totally r e m o v e d and b o t h p r o v e d to be alveolar hydatid cysts. A n unusual feature in this case is C T and M R I d e m o n s t r a t i o n of dural and b o n y extension.

or c o n t a m i n a t i o n by plants or infected water. In h u m a n beings, the liver is the first site. O t h e r p r i m a r y sites are reported: kidney [3], brain [14, 15], and b o n e [4], but secondary lesions are m o r e f r e q u e n t in lung, h e a r t [1], brain, skull, ribs, m e d i a s t i n u m and even the lacrimal gland [16]. We r e p o r t a patient with intracranial and right p a l p e b r a l lesions t r e a t e d by surgery.

Key words: Brain - C T - M R - A l v e o l a r echinococcosis Echinococcns multilocularis

Case report

A l v e o l a r echinococcosis is a parasitic disease caused by E c h i n o c o c c u s multilocularis. This infection is w i d e s p r e a d in cold countries, such as A l a s k a [1-3], several n o r t h e r n central states of the U S A [4, 5], central E u r o p e [6, 7], Russia [3, 8], China [9] and T u r k e y [10, 11]. G a b r i e l [12] rep o r t e d 153 F r e n c h cases. Canines are the m a i n host, esped a l l y the fox, b u t in France also the m u s k r a t [13]. M a n is accidentally infected either by direct contact with rodents

A 48-year-old farmer from a rural area complained of headache and a right palpebral mass. He had undergone a right upper lobectomy 8 years previously for a pulmonary alveolar hydatid secondary to a liver infection, treated by right hepatectomy. There was no neurological deficit and no eosinophilia was found. CT (Fig. 1) revealed a right frontal mass containing ring and nodular calcification and small cysts, surrounded by marked oedema and causing mass effect (displacement of the lateral ventricle, corpus callosum and falx cerebri). This mass showed heterogeneous contrast enhancement. Frontal bony erosion was present. MRI (Fig. 2) showed a large frontal mass,

Fig. la-c. Contrast-enhanced CT. A rounded right palpebral mass is seen (1). There is a large right frontal mass, with posterior displacement of the corpus caiiosum, posterior and contralateral displacement of the right frontal horn and contralateral displacement of the falx cerebri. The mass contains nodular and ring calcification, shows partial contrast enhancement and is surrounded by oedema (2). Unenhancing and noncalcified areas represent parasitic cysts (3). Anterior to the mass the inner table of the skull is irregular (4)

Correspondence to: J.L.Dietemann, Service de RadiologieB, Hfpital Civil, Pavilion Clovis Vincent, Hfpitaux Universitaires, F-67091 Strasbourg Cedex, France

290 posterofrontal areas. Dissemination is thus p r o b a b l y not haematogenous type; white or grey matter and the cortex m a y be affected. The lesions m a y be multifocal [10, 14, 17, 18, 21] or solitary [9, 11, 22, 23]. Two features distinguish brain from liver lesions: extirpation of masses in the brain is easier, due to their better defined margins [24]; a higher proportion of cases show protoscoleces [7, 9, 10, 21, 24, 28]. Brain lesions m a y appear as late as 10 years after the onset of the disease. The CT and M R I appearances of echinococcosis multilocularis have rarely been reported [10, 23, 29]. O n CT, Echinococcus rnultilocularis appears as a grape-like, multilocular, cystic mass with definite margins; calcification and surrounding o e d e m a are common; contrast e n h a n c e m e n t occurs within the inflammatory reaction around the cysts [10, 23]. Differential diagnosis f r o m glioma, particularly oligodendroglioma m a y be considered; however, the grape-like appearance should lead to the diagnosis of Echinococcus multilocularis. W h e n calcification is absent, ring-like enhancement m a y be seen [10], raising the p r o b l e m of differential diagnosis f r o m bacterial abscess and tuberculoma; the latter generally have lower central attenuation than alveolar hydatid cysts.

Fig.2. On a Tl-weighted MR image (a) the mass gives heterogeneous low signal; it shows heterogeneous contrast enhancement (b,c). The inner table of the cranial vault appears irregular (1) and dural enhancement (2) is seen. The calcified areas give Iow signal. There is ring enhancement of the low intensity palpebral mass, which gives high signal on a T2-weighted image (d). On proton density (e) and T2-weighted images a grape-like low signal frontal mass was demonstrated; the surrounding oedema gives high signal

with heterogeneous low signal on Tl-weighted sections. T2weighted images revealed a multilocular low intensity mass surrounded by a large area of high signal, corresponding to oedema. A sagittal section confirmed the right palpebrat cystic mass. There was heterogeneous contrast enhancement, which extended to the dura mater and frontal bone. The two masses were removed at surgery, which confirmed bony and duralinvolvement. Flumendazol medication was given. Six months later MRI showed no sign of recurrence.

Discussion

The first alveolar hydatid lesion in the brain was reported in 1884 [17]. M a n y necropsy series were described subsequently [7, 18] but the incidence of this disease is difficult to assess. Clement et al. [19] reported 37 cases ( 6 % ) of intracranial alveolar echinococcal disease a m o n g 600 cases collected in G e r m a n y and Russia between 1936 and 1960; Allemand and Miguet [20] estimated the frequency to be 5 %; in Gabriel's series it was 3.9 % [12]. Only 16 surgically treated cases are reported [9, 10, 15, 21-27]. However, the location of the lesions, documented in only 11 cases, was as follows: four in the parietal region, three in the t e m p o r a l lobe and four in the frontal and/or

The CT and M R I appearances of alveolar hydatic disease involving the brain are characteristic, and diagnosis is simple when the primary location is known. Correlation with serological tests (immunofluorescence, passive haemagglutination tests, E L I S A , immunoelectrophoresis with antigenic extracts of Echinococcus muttilocularis) [1, 29, 30, 31] m a y be important. Treatment includes surgical removal and flumendazol medication to prevent recurrence. Disseminated, multifocal brain lesions, development of distant implantations and failure to remove the primary focus are three main causes of a p o o r outcome.

References

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