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| LETTER TO EDITOR |
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| Year : 2012 | Volume
: 60
| Issue : 2 | Page : 242-243 |
Posterior fossa extradural hydatid cyst with septae and calcification
S Bhaskar, Ajay Choudhary, Amit K Singh
Department of Neurosurgery, PGIMER and Dr. RML Hospital, New Delhi, India
| Date of Submission | 09-Mar-2012 |
| Date of Decision | 10-Mar-2012 |
| Date of Acceptance | 11-Mar-2012 |
| Date of Web Publication | 19-May-2012 |
Correspondence Address:
S Bhaskar
Department of Neurosurgery, PGIMER and Dr. RML Hospital, New Delhi
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/0028-3886.96426
How to cite this article:
Bhaskar S, Choudhary A, Singh AK. Posterior fossa extradural hydatid cyst with septae and calcification. Neurol India 2012;60:242-3 |
Sir,
Hydatid disease is a zoonosis caused by larval stage of Echinococcus granulosus or Echinococcus multilocularis and is common in sheep farming countries in Asia, Africa, South and Central America, and the Mediterranean area. [1] Central nervous system (CNS) echinococcosis is rare and accounts for 2-3% of total body localizations. [2] Among these, the posterior fossa lesions, particularly the extradural ones, are very rare and only five cases have been documented till date. Calcification is also seen in only 1% of the cysts. [3]
A 40-year-old woman presented with 1 year history of holocranial headache which had increased in severity over the past few days with vomiting. She also reported disturbances in her gait over the past 5 months. On examination, she had papilledema with right-sided cerebellar signs and gait ataxia. Computed tomography (CT) head revealed a large cystic extra-axial mass lesion with internal septations and peripheral calcification in the right posterior fossa with obstructive hydrocephalus [Figure 1]a. Patient underwent emergency ventriculoperitoneal shunt. Magnetic resonance imaging (MRI) of brain revealed a large cystic extradural lesion in the right posterior fossa, which was hypointense on T1-weighted image [Figure 1]b, hyperintense on T2-weighted image with hypointense peripheral rim [Figure 1]c, without restriction on diffusion weighted image [Figure 1]e, and with a thin rim of contrast enhancement on post-contrast images [Figure 1]d. Contrast CT chest and abdomen did not reveal any hydatid cysts. Patient underwent right suboccipital craniectomy with excision of cyst. There were multiple cysts in the extradural space with thin walls, containing transparent fluid. Postoperative course was uneventful [Figure 2]a. Histopathologic examination of the cyst revealed hydatid cysts characterized by laminated and germinal layer with multiple protoscolices attached to germinal layer [Figure 2]b. Patient was prescribed albendazole 400 mg twice a day for 4 weeks. There was minimal gait problem at 2 months follow-up. She is doing well at 6 months follow-up and is without any recurrence of symptoms.  | Figure 1: (a) NCCT head axial images showing extradural multiseptate hypodense cystic lesion in posterior fossa with peripheral and septal calcification. (b) T1W image showing hypointense lesion (c) T2W image showing hyperintense lesion with thin hypointense periphery. (d) T1 post-contrast image revealing thin peripheral rim of enhancement. (e and f) DWI and apparent diffusion coefficient showing no restriction
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 | Figure 2: (a) Postoperative NCCT head showing total removal of the cyst. (b) Photomicrograph of tissue specimen showing multiple protoscolices attached with inner germinal layer and laminar layer external to germinal layer, suggestive of hydatid cyst
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Three forms of intracranial CNS hydatid disease occur: intracerebral, cranial extradural, and a combined form. [1] Cranial epidural hydatid disease is extremely rare as the physiologic flow of blood to brain is mainly through the internal carotid system, and therefore the likelihood of the larvae traveling through the external carotid system is very low. The E. granulosus cycle involves two hosts: intermediate hosts, usually sheep, camel, or swine, and the definitive hosts such as dog or fox. Occasionally, humans can be accidental intermediate hosts through contact with infected dogs or by oral ingestion of garden vegetables infected by the eggs of the parasite. Liver and lungs act as a big filter of the portal system. Usually, CNS hydatid disease is associated with or followed by hydatid disease of other body organs (liver 59-75%, lungs 8.5-43%). Occurrence of cranial posterior fossa extradural hydatid disease without involvement of other body organs is extremely rare as seen in our patient. In hydatid cysts, absence of surrounding edema is usual and calcification is rare. [3] In our patient, there were multiple internal septations as well as peripheral and internal septal calcification. Alveolar echinococcus (E. multilocularis) is more associated with calcification, perilesional edema, and enhancement, as compared to the more common E. granulosus. Intracranial hydatid cyst may also be classified as primary or secondary. The primary cysts are formed as a result of direct infestation of the larvae in the brain without demonstrable involvement of other organs. The primary cysts are fertile as they contain scolices and brood capsules; hence, rupture of primary cyst can result in recurrence. The secondary multiple cysts result from spontaneous, traumatic, or surgical rupture of the primary intracranial hydatid cyst, and they lack brood capsule and scolices. Only 28 cases of cranial epidural space have been described till 2009. [1] Among these, only five cases of posterior fossa extradural cysts have been reported till date. [4] Brain manifestations of hydatid cysts are seven times more common in children than in adults. Cerebral hydatid cysts are usually located supratentorially in the middle cerebral artery territory. However, cranial epidural hydatid cysts seem to have a tendency to occur around the midline. It has been hypothesized that this may be due to the existence of a rich venous vascularization in the midline. In our patient, hydatid cyst was in the epidural space in the posterior fossa, away from the midline, and with septae and calcification.
| » References | |  |
| 1. | Cemil B, Tun K, Gurcay Ag, Uygur A, Kaptanoglu E. Cranial epidural hydatid cysts: clinical report and review of the literature. Acta Neurochir (Wien) 2009;151:659-62. 
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| 2. | Turgut M. Intracranial extradural hydatid cysts: Review of the literature. Acta Neurochir 2010;152:1805-06.
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| 3. | Tlili-Graiess K, El-Ouni F, Gharbi-Jemni H, Arifa N, Moulahi H, Mrad-Dali K. Cerebral hydatid disease: Imaging features. J Neuroradiol 2006;33:304-18.
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| 4. | Lakhdar F, Arkha Y, Bourgrine M, Derraz S, El Ouahabi A, El Khamlichi A. Posterior fossa extradural and extracranial hydatid cyst. Neurochirurgie 2010;56:391-4.
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[Figure 1], [Figure 2]
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