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Year : 1999  |  Volume : 9  |  Issue : 2  |  Page : 73-76
Images - primary spinal echinococcosis


Department of Radiology, B.J.M.C. and Civil Hospital, Asarwa, Ahmedabad-380016, Gujarat, India

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Keywords: Spine, Echinococcus, MRI, CT

How to cite this article:
Desai HJ, Bhatt CJ, Dave BA. Images - primary spinal echinococcosis. Indian J Radiol Imaging 1999;9:73-6

How to cite this URL:
Desai HJ, Bhatt CJ, Dave BA. Images - primary spinal echinococcosis. Indian J Radiol Imaging [serial online] 1999 [cited 2019 Nov 12];9:73-6. Available from: http://www.ijri.org/text.asp?1999/9/2/73/28337
Spinal echinococcosis is rare even in areas where echinococcosis is endemic. We present a case of primary thoracic spinal echinococcosis with resultant cord compression. Imaging findings on plain radiographs, myelography, CT-myelography and MR are discussed. We emphasize that echinococcosis of the spine should be considered in the differential diagnosis when radiological findings suggest spinal infection or tumor. MR is the study of choice in the diagnosis of spinal echinococcosis.

A forty-nine-years old man presented with complaints of backache for two months, weakness in both lower limbs for one month and inability to walk at the time of admission. Neurological examination revealed spasticity in both lower limbs, absent muscle power in the lower limbs and hyperreflexia in the knee and ankle joints. Plantar reflexes were extensors. There was hypoesthesia below D12 and anesthesia below D10 with involvement of the bladder and bowel.

Plain radiographs of thoracic spine showed well-defined osteolytic areas in multiple vertebral bodies in the upper and mid-dorsal regions. [Figure - 1]. No collapse of the vertebral bodies was seen. The inter-vertebral disc spaces were normal. An abnormal right-sided paraspinal soft tissue mass was seen. Skeletal survey and US of the abdomen revealed no abnormality. This was followed by myelography, which showed a complete block at D5-D6 with a characteristic brush-border appearance suggestive of an extradural lesion [Figure - 2].

CT-myelogram showed multiple osteolytic lesions in the vertebral bodies from D2 to D9 with extension into some of the appendages. The right fifth and sixth ribs were involved. A lobulated paravertebral soft tissue mass was seen on the right side with intraspinal extension from D4 to D7. There was no enhancement of the soft tissue mass or bony margins on intra-venous contrast injection. The density of the central component of the soft tissue mass corresponded to cystic areas (12 HU). The spinal cord was pushed to the left and posteriorly by the intraspinal soft tissue mass [Figure - 3]. MR of the dorsal spine showed multiple well-defined, rounded hypointense areas involving the D3 to D9 vertebral bodies on the axial and sagittal T1W SE [Figure - 4] images which appeared hyperintense on T2W images [Figure - 5]. The vertebral appendages and the right fifth and sixth ribs showed multiple cysts. Intraspinal extension of the cyst was seen from D4 to D7 with cord compression. Multiple loculated cysts were seen in the right paraspinal region at D4-D5. MR findings were diagnostic of echinococcosis of the thoracic spine with multi-level involvement. The patient was operated and histopathological findings confirmed the diagnosis. The patient was put on antihelminthic therapy.

Echinococcosis is a condition caused by the cyst stage of infestation by the tape-worm Echinococcus granulosus. The adult form of the parasite lives in the intestinal tract of the canines, whereas sheep, cattle and humans are intermediate hosts. Echinococcal cysts are mostly located in the liver but can affect any organ of the infected host except hair, teeth and finger nails [1] The liver and lung are commonly involved. Echinococcus affecting the bone is a rare condition. Its incidence ranges from 0.5% to 2% of all cases of echinococcosis. The bones most often involved are vertebrae (44%) [2]. Echinococcal disease in the bones occurs mostly in vascularized areas. The vertebrae, long bone epiphyses, ilium, skull and ribs are involved in decreasing order of incidence. In the spine, the thoracic region is most commonly affected [3]. In bones, there is no pericyst formation and the parasite expands by exogenous proliferation in an irregular branching pattern along the lines of least resistance, especially the bony canals. Bone resorption is due to pressure erosion and local necrosis caused by impairment of blood supply. Bone disease presents later than soft tissue echinococcal disease. It produces well-defined, multiloculated osteolytic lesions resembling a bunch of grapes on plain radiographs [4]. Spinal disease involves vertebral bodies, appendages, contiguous ribs and paravertebral tissue. Involvement of contiguous ribs is highly suggestive of echinococcosis. There is expansion of the bone with absence of periosteal reaction and sclerosis. Intervertebral disc spaces are spared but may occasionally be involved [5]. In our case, these features were well demonstrated. The intervertebral disc spaces were normal.

CT in spinal echinococcosis shows multiple osteolytic lesions in the vertebral bodies, appendages and ribs. Intravenous administration of contrast medium does not show enhancement of the paraspinal and intraspinal soft tissue mass and bony margins. This is characteristic of echinococcal disease [6]. CT myelogram helps to demonstrate cord compression. CT thus provides precise anatomical localization of the lesion. These features were well-demonstrated in our patient. The differential diagnosis of multiple myeloma, metastases and spinal infection should be considered when such features are seen on CT.

MR in spinal echinococcal disease shows multiple cysts, isointense to CSF on T1 and T2W images [7]. These are seen in the vertebral bodies, appendages and ribs with intraspinal extension of the lesion. These findings were well-characterized in our patient. Echinococcosis in paravertebral soft tissues behaves as in other soft tissues and grows by endogenous vesiculation with radial expansion to produce spherical cysts with daughter cysts within the parent cysts. The soft tissue component is better seen and characterised on MR. On T1W images the daughter cysts have a lower signal intensity than the mother cyst. On the first echo of the T2W images, the mother cyst has a signal higher than that of the daughter cyst, both having similar signal intensities on strong T2W images [9]. In our case the mother cyst showed increased signal intensity on strong T2W images which was different from the signal intensity in the daughter cyst. A well-defined, low intensity continuous rim is often seen surrounding the echinococcal cyst on T1W and T2W images composed primarily of collagen [10]. In our case this was well demonstrated.

 
   References Top

1.Ismail MA, Al-Dabagh MA, Al-Janabi TA et al . The use of computerised axial tomography (CAT) in the diagnosis of hydatid cysts. Clin Radiol 1980; 31: 287-290.   Back to cited text no. 1    
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5.Claudon Michel, Bracard Serge, Plenat Francois, Regent Denis, Bernadac Pierre, Picard Luc. Spinal involvement in alveolar echinococcosis: assessment of two cases. Radiology 1987; 162: 571-572.   Back to cited text no. 5    
6.Braithwaite Peter A, Lees Richard F. Vertebral hydatid disease: radiological assessment. Radiology 1981; 140: 763-766.   Back to cited text no. 6    
7.Coates R, Von Sinner, W. Rahm R. Magnetic resonance imaging of an intracranial hydatid cyst. Am J Neuroradiol 1990; 11: 1249-1250.   Back to cited text no. 7    
8.Kalovidouris-A, Gouliamos-A, Vlachos-L et al . MRI of abdominal hydatid disease. Abdom Imaging 1994; 19: 489-94.   Back to cited text no. 8    
9.Taourel P, Marty-Ane B, Charasset S, Mattei M, Ph.Devred and Bruel JM. Hydatid cyst of the liver:comparison of CT and MRI. J Comput Assist Tomogr 1993; 17: 80-85.   Back to cited text no. 9    
10.Severino A, Marani Davolio, Canossis Giancarlo C, Nicoli Franco A, Alberti Gianpiero P, Monni Sebastiano G et al . Hydatid disease: MR imaging study. Radiology 1990; 175: 701-706.  Back to cited text no. 10    

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Correspondence Address:
Hemali J Desai
211/B, Kothawala Flats, Pritamnagar, Ellisbridge, Ahmedabad 380 006
India
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Source of Support: None, Conflict of Interest: None


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[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5]

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