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Primary
Spinal Epidural Hydatid Cyst - A Case Report
Miloudi Gazzaz, Ali Akhadar, Said Derraz, Driss Mdaghri, Abdelslam El Khamlichi |
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A rare case of primary intraspinal extradural hydatid cyst of the thoracic
region with spinal cord compression is reported. The diagnosis was established
preoperatively on the basis of the magnetic resonance imaging (MRI) findings.
The patient underwent surgery and antihelminthic treatment and recovered
completely.
Hydatid disease of the spine occurs in 1% of all cases with hydatidosis and is most commonly located in the thoracic spine. Isolated epidural hydatid cyst are rare and only a few cases have previously been reported.
A 10-year-old boy, with unremarkable past medical history, was referred to our institution in April 1999 with a history of slowly progressive weakness of lower limbs and sphincter dysfunction that had developed over a 6-month period. Physical examination revealed flaccid paraplegia, there was a T10 sensory level, hyporeflexia and position sense was affected. Magnetic resonance imaging (MRI) showed a cystic mass in the lower thoracic area facing T10-11. This mass is located in the epidural space compressing the spinal cord which was displaced anteriorly. Its signal intensities on both T1- and T2- weighted images corresponded to a cystic lesion (Fig. 1). Plain films and CT scans confirmed absence of bone's involvement. This radiologic aspect was suggestive of an arachnoid cyst. Biologic parameters were without abnormalities. At operation, the laminas of T10 and T11 were removed bilaterally confirming its cystic nature, adequate dissection permitted removal of an unruptured hydatid cyst. Chest x-ray and abdominal echography showed no other location of hydatidosis. Postoperative course has been uneventful with progressive resolution of neurologic symptoms. Postoperative treatment included rehabilitation and chemotherapy with Albendazole 10 mg/kg 1 day in four 1-month courses, separated by 15 days intervals. Partial recovery of his neurologic deficit was observed after a follow-up of 12 months.
Hydatid disease (HD) is prevalent in the developing countries. Due to travel and migration, this disorder, which is virtually unknown in western countries, is becoming more prevalent.12 It affects equally both sexes but mainly the younger population. An important point is that nearly 50% of the patients are under the age of 30 years.7-14 The infestation occurs either by direct ingestion of parasitic eggs from contact with dogs or indirectly from contamined water or food.4 There are no pathognomonic signs and symptoms of spinal hydatid disease.12 The diagnosis is considered if the patient lives in a geographic region where the infestation is known to occur or if he has migrated from or visited an endemic area.12 The parasite being carried through the porto-vertebral venous shunts when the intra-abdominal pressure increases (it often begins in the vertebral body).4,8,10 HD in bone differs from disease in soft tissue in that growth occurs along the line of least resistance, particularly along the interbecular spaces, with the formation of diverticulated cysts that may form by exogenous vesiculation.3 The parasite grows multilocularly because of a lack of defensive reaction of the bony tissue when the cyst breaks out of the vertebral body. It may extend into the extradural space or into any of the paraspinal tissues.4,10 As the larvae enlarge, there is dilatation of the bony spaces of the spongiosa and resorption of the cancellous bone. There is no development of an adventitious layer or pseudocapsule, which occurs in soft tissues where the cyst usually grows by endogenous vesiculation and radial expansion to produce a spherical cyst with compression of host tissue.3 However, cysts in paravertebral and intraspinal spaces behave as they do in soft tissues and produce a spherical cyst tissue.5 It is believed that the signs and symptoms often became worse once the cyst breaks out of the bone.12 As the primary site of the infestation and the precise extent of the disease are very difficult to verify, Braithwaite and Lees have classified this disease into 5 types:3 1) primary intramedullary hydatid cyst; 2) intradural extramedullary hydatid cyst; 3) extradural intraspinal hydatid cyst; 4) hydatid disease of the vertebra; and 5) paraspinal hydatid disease. We agree with this classification, which is quite useful and we can classify our patient as type 3. To our knowledge only one case of true intramedullary cyst has been reported in the literature.8 Intradural extramedullary cysts are also rare, only 14 cases have been collected until 1991.9 This rare observation requires some comments: Primary solitary epidural hydatid cyst affecting the spinal cord is an exceptional possibility.1,13 This disease has no specific characteristics as regards other more common causes of spinal cord compression, its diagnosis, as in our case, is often available only at the time of surgery.1 This would provide complete recovery if the cyst is delivered unruptured. MRI is used to delineate the anatomical relationships precisely and should be used for the diagnosis of spinal hydatid disease like many other types of spinal pathology. Hydatid cysts have an almost unique appearance on MRI.2 They are spherical and their walls are very thin and regular with no septation. On T1-weighted images the cyst wall may be isointense or give slightly lower signal than its contents and T2-weighted images demonstrates a low intensity rim surrounding the homogenous high-signal cyst content.2 Operative procedures are the treatment of choice for spinal cord compression by hydatid cysts. Vertebral hydatid disease can be considered a local malignant tumour.6 Ideally, treatment would be by total excision of all affected tissue, but this is impossible. Palliative resection of the diseased focuses through a posterior, or rarely an anterior approach, which is the usual surgical procedure chosen.5 Spinal cord decompression is the main purpose of the intervention.7 However, rare isolated intradural or epidural cysts without bone involvement could be removed unruptured.2 Antihelminthic treatment is indicated even when no breaking of the cyst is induced during surgery, because microinfiltration of the vertebrae cannot be shown on radiological exploration. Bone infiltration makes the radical excision difficult and subsequently there is a high incidence of re-currence.11 Among 20 cases of spinal hydatid disease treated in our department during the last 14 years, we found only one case of isolated epidural hydatid cyst without bone involvement. The antihelminthic treatment seems to change the course of this disease, 6 among our 20 patients who received it are still living without evidence of recurrence during a period ranging from between 1 to 6 years. |
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Correspondence: Dr. Miloudi Gazzaz, Department of Neurosurgery, Hopital des Specialites ONO, CHU de Rabat Sale, BP 6444, Rabat Instituts, Rabat, Morocco Fax: (202) 7 770 212 - Email: gazzazmiloudi@hotmail.com |
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http://www.panarabneurosurgery.org/ |
