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NEURORADIOLOGY Table of Contents   
Year : 2006  |  Volume : 16  |  Issue : 4  |  Page : 727-732
CT and MRI features of the typical and atypical intracranial hydatid cysts: Report of five cases


Department of Radio diagnosis & Imaging, B. J. Medical College, Civil Hospital, Ahmedabad, India

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Date of Submission07-Sep-2006
Date of Acceptance10-Aug-2006
 

Keywords: hydatid, intracranial, CT, MRI

How to cite this article:
Ravalji M, Kumar S, Shah A K, Vaghela D U, Makwana G J, Singh K. CT and MRI features of the typical and atypical intracranial hydatid cysts: Report of five cases. Indian J Radiol Imaging 2006;16:727-32

How to cite this URL:
Ravalji M, Kumar S, Shah A K, Vaghela D U, Makwana G J, Singh K. CT and MRI features of the typical and atypical intracranial hydatid cysts: Report of five cases. Indian J Radiol Imaging [serial online] 2006 [cited 2019 Aug 24];16:727-32. Available from: http://www.ijri.org/text.asp?2006/16/4/727/32333
Intracranial hydatid cysts are extremely rare, accounting for only 1-2% of all intracranial space occupying lesions [1], even in countries where this disease is endemic - the middle east, Mediterranean countries, South America, North Africa and Australia [2].

In India, the hydatid disease is more commonly seen in the Kurnool district of Andhra Pradesh, Madurai district of Tamil Nadu and in Punjab [3]. Incidence of intracranial hydatid in India is 0.2 % [3].

The typical intracranial hydatid cysts, caused by Echinocccus granulosus, present as well defined solitary cystic lesions in the middle cerebral artery territory [4], without surrounding edema, are non enhancing and show unremarkable mass effect unless large [5] when they can show significant parenchymal distortion, mass effect, hydrocephalus, and raised intracranial pressure.. Lesions can present as multicystic masses, with mass effect or with edema, when differentiation may be difficult from other entities like astrocytoma, infective lesions etc [5]. Multiple cysts can develop rarely either spontaneously, after trauma or post operatively [2],[5],[6].

Case 1: The typical large hydatid cyst: An eight year old boy presented with convulsions since two years and gradually increasing left hemi paresis without any significant constitutional symptoms. On CT scan, a large, well defined, oval, CSF density, non enhancing cystic lesion without any discernible wall and causing mass effect and midline shift towards the opposite side was seen [Figure - 1],[Figure - 2].

The cerebral hydatid cysts are slow growing and present late when they increase in size and become large. Growth rate has been variably reported between 1.5-10 cm/year [1],[7]. Hydatid cysts are generally found in middle cerebral artery territory (4) in the parietal lobes, although they can be seen in any location including skull vault, extradural, intraventricular, meningeal, posterior fossa and brainstem [5].

Children are more commonly affected than adults [1],[8].

Generally they are unilocular, CSF density(on CT) or intensity (on MRI) lesions with a fine fibrous wall which on T2WI MR scans appears as hypointense ring; this appearance being considered diagnostic [5].

Calcification is seen in less than one percent of cases [5] and is better seen on CT. Hemorrhage has not been reported.

The cysts lie just few millimeters below the cortex [7] and can protrude and adhere to the meninges [5],[6] and calvaria and erode the vault [5]. Surrounding sclerosis may be present as well at the periphery [5].

Case 2: A six year old girl had come with convulsions, headache and vomiting and papilloedema increasing since last four months. CT scan of the brain showed a large hemispherical cystic lesion in the right fronto-temporo-parietal region. Smaller cystic lesions were present on calvarial aspect of the cyst, these daughter cysts having had thicker walls. No peripheral wall could be seen. There was minimal enhancement of the walls of the daughter cysts but not of the mother cyst on post contrast study [Figure - 3],[Figure - 4].

Surgery revealed a large cyst with multiple daughter cysts within. The lesion was adhered to the dura and was eroding the skull. This patient had a liver hydatid as well while the other cases presented in this series had normal chest radiographs and abdominal sonograms.

Daughter cysts have similar features as the mother cyst though they are less hyperintense on T2W MR image than the mother cyst [5].

Intracranial hydatid cysts are classified as primary or secondary depending on whether other organs haven't/have been involved. Primary hydatid cysts contain brood capsule and scolices and their rupture can produce secondary cysts which lack scolices and brood capsules. Primary multiple cysts are rare [9],[10] most being secondary, whether they have developed spontaneously or after embolization from rupture of a primary cyst [7].

The scolices of the cyst are not seen on MRI [6],[9],[11].

Case 3: A 30 yrs old female patient presented with generalized headache since last three years without any fever, weakness, focal neurological deficits or other significant complains. Plain CT brain showed a well defined hypodense lesion with a smooth thin ring and moderate surrounding edema with mild midline shift towards opposite side.. There was enhancement of the ring on post contrast study. A diagnosis of abscess was given however during surgery an unruptured hydatid cyst popped out. Histopathology reconfirmed the diagnosis. There was no evidence of infection.

Edema is not a feature of intracranial hydatids. When present, edema and post contrast enhancement indicate ongoing inflammation [12]. Presence of significant edema may indicate rupture of the cyst and may be present in post operative cases. Such cases are difficult to differentiate from other cystic lesions with enhancement and peripheral edema such as abscesses, large granulomas or cystic gliomas [5].

Kohli et al [13] performed in vivo MR spectroscopy (MRS) studies in a patient of intracranial hydatid cyst and found, besides lactate, alanine and acetate, a large resonance for pyruvate. The MRS pattern appeared different from the other cystic lesions of brain and they have suggested MRS as an adjunct to imaging in the differential diagnosis of intracranial hydatids.

Garg M et al [14] have done ex vivo study on hydatid fluid and found that they donot contain creatine unlike cysticerus cysts, and if fertile, they also contain malate and,or fumarate.

There have not been complete in vivo MR spectroscopy studies to give an acuurate formulation of the findings although it has shown promise in differentiating hydatid didease from other confusing entities.

Case 4: A 14 year female presented with complains of nausea, vomiting and giddiness since last 4 months. MRI showed a multicystic lesion with thin septae involving the brainstem and fourth ventricle. The cyst contents were slightly hyperintense to CSF on T1WI and hyperintense on T2WI. There was no surrounding edema. Hydrocephalus was present. A differential diagnosis of epidermoid cyst, cystic glioma and hydatid was considered. Surgery revealed the diagnosis of hydatid cyst however. Patient had died on the first post-operative day.

Other differentials apart from infective lesions and astrocytomas are an epidermoid, an arachnoid cyst and a porencephalic cyst.

Arachnoid cyst has similar appearance as that of a hydatid but they are said to have an irregular inner border [15] and are not spherical shaped.

Epidermoids can be differentiated usually by their lobulated, vessel engulfing, self moulding behaviour however in certain situations, as the above example, diagnosis can be difficult.

Case 5: A 23 yrs old male presented with complain of convulsion since last six months. MRI brain showed a multicystic lesion in the left temporal lobe. The lesion appeared hypointense on T1WI and hyperintense on T2WI. No adjacent edema was evident. A differential diagnosis of glioma or hydatid was considered.

During surgery a firm tumour like lesion was seen and complete removal of the lesion needed some sacrifice of surrounding brain tissue as well.

The pathological sample had revealed multivesicular (alveolar) hydatid cyst which is caused by E. multilocularis.

Cerebral alveolar hydatid cyst is extremely rare. These lesions produce firm masses full of connective tissue and produce perilesional edema although they are well demarcated [16]. Solid enhancing areas and calcification are often present [17],[18],[19].

Intracranial extracerebral hydatid cysts are rare and may occur in three forms [4,16]: (i) cranial: usually the bony spongiosa is the first to be involved; (ii) cranial extradural: the extradural space may be infected by embolization of scolices or embryos via blood vessels, by extrusion of intracerebral cysts via healthy dura mater or by erosion of osseous hydatid into the extradural space; (iii) combined: there may be simultaneous intracerebral, extradural, and bony cysts. Of the three forms, extradural variety is extremely rare as the physiologic flow of blood to the brain is mainly through the internal carotid system, so the likelihood of the larvae travelling through the external carotid system is very low [20].

 
   References Top

1.Erashin Y, Mutluer S, Guzelbag E : Intracranial hydatid cysts in children. Neurosurgery 1993; 33 : 219-224.   Back to cited text no. 1    
2.Onal C, Orhan B, Metis O et al : Three unusual cases of intracranial hydatid cysts in paediatric age group. Pediatr Neurosurg 1997; 26 : 208-213.   Back to cited text no. 2    
3.Dharker SR : Hydatid disease. In : Text Book of Neurosurgery, 2nd edition. Eds. Ramamurthi B, Tandon PN. Churchill Livingstone, New Delhi 1996; 535-544.  Back to cited text no. 3    
4.Ba'assiri A, Haddad FS. Primary extradural intracranial hydatid disease. CT appearance. AJNR 1984; 5: 474 -475.   Back to cited text no. 4    
5.Pinar Polat, Mecit Kantarci, Fatih Alper et al. Hydatid disease from head to toe. Radiographics 2003;23:475-494.  Back to cited text no. 5    
6.Gupta S, Desai K, Goel A. Intracranial hydatid cyst : a report of five cases and review of literature. .Neurology India 1999; 47: 214-7.  Back to cited text no. 6    
7.Sierra J, Oviedo J et al. Growth rate of secondary hydatid cysts of the brain. Neurosurgery. 1985; 62: 781-782.  Back to cited text no. 7    
8.Jimenez-Mejias ME, Castillo-Ojeda E, Cuello-Contreras JA et al : Cerebral hydatidosis. Analysis of a series of 23 cases. Med Clin (barc) M 1991; 97:125132.   Back to cited text no. 8    
9.Nurchi G, Francesco F, Montaldo C et al : Multiple cerebral hydatid disease : case report with magnetic resonance imaging study. Neurosurgery 1992; 30 : 436-438.  Back to cited text no. 9    
10.Sharma A, Abraham J : Multiple giant hydatid cysts of the brain-case report. Neurosurgery 1982; 57 : 413-415.  Back to cited text no. 10    
11.Coates R, Von Sinner W, Rahm B : MR imaging of an intracranial hydatid cyst. AJNR 1990; 11 : 1249-1250.  Back to cited text no. 11    
12.Karak PK, Mittal M, Bhatia S et al : Isolated cerebral hydatid cyst with pathognomonic CT sign. Neuroradiology 1992; 34 : 9-10.  Back to cited text no. 12    
13.Kohli A, Gupta RK, Poptani H et al : In vivo proton magnetic resonance spectroscopy in a case of intracranial hydatid cyst. Neurology 1995; 45 : 562-564.  Back to cited text no. 13    
14.Monika G, Sanjeev C, Kashi N et al. Differentiation of hydatid cyst from cysticercus cyst by proton MR spectroscopy. NMR in Biomedicine 2002; 15: 320-326.  Back to cited text no. 14    
15.Banna M. Arachnoid cysts on computed tomography. AJR 1976; 127: 979-982.   Back to cited text no. 15  [PUBMED]  
16.Tahsiyn Erman, Metin Tuna, I˙skender Gocer et al. Intracranial intraosseous hydatid cyst, Case report and review of the literature. Neurosurg. Focus 2001;Volume 11:1-3.  Back to cited text no. 16    
17.Yasar B, Serdar K, Hasan N et al. Cerebral hydatid disease, CT and MR imaging findings. Swiss Med Wkly 2004;134:459-467  Back to cited text no. 17    
18.Tunaci M, tunaci A, Engin G. MRI of cerebral alveolar echinococossis. Neuroradiology 1999; 41: 844-846.  Back to cited text no. 18    
19.Bensaid AH, Dietemann JL et al. Intracranial alveolar echinococossis. Neuroradiology 1994; 36:289-291.  Back to cited text no. 19    
20.Sardana VR, Dharker SR, Mittal RS et al : Multiple intracranial hydatid cysts. Neurol India 1991; 39 : 205  Back to cited text no. 20    

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Correspondence Address:
M Ravalji
Room No-6, D-10, PG Doctor's Hostel, Civil Hospital Building, Asarwa, Ahmedabad-380016
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0971-3026.32333

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    Figures

  [Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5], [Figure - 6], [Figure - 7], [Figure - 8], [Figure - 9], [Figure - 10], [Figure - 11], [Figure - 12], [Figure - 13]

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