Spinal hydatid disease, a rare but existent pathological entity: case report and review of the literature.

Abstract: Spinal hydatid disease is a not uncommon cause of spinal cord compression in endemic countries; however, involvement of the epidural space with sparing of the vertebral column is rare. Early diagnosis and surgical decompression with total removal of the hydatid lesion, when possible, is generally considered the standard of care for this disease. The authors describe a case of massive epidural hydatid disease without involvement of the vertebral column in a 62-year-old male patient, treated with a 2-stage surgical operation and administration of systemic albendazole. The literature is reviewed regarding the clinical features, diagnosis, treatment and prognosis of spinal echinococcosis.

Key Words: albendazole, cauda equina, epidural, laminectomy, spinal hydatid disease

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Hydatid disease (echinococcosis), although rare in northern Europe and the United States, is a considerable cause of morbidity in large geographic regions. The disease is endemic in the Middle East, the Mediterranean, South America, Australia, India and Northwest China, (1-5) with an incidence that ranges from 3 to 50 cases per 100,000 inhabitants. (6-8) Hydatidosis is located in the bones in 0.5 to 2% of all cases; (9-13) approximately 50% of these involve the spine. (1,5,9,11,12,14)

Infestation with the tapeworm Echinococcus granulosus accounts for the overwhelming majority of cases of hydatid disease. Echinococcus multilocularis may be the causative agent in rare cases. Dogs and rarely other carnivores are the definitive hosts of E. granulosus. Sheep and other herbivore animals may become infected by ingesting ova passed in the feces of the dog; these are the intermediate hosts. The cycle is completed when dogs eat the infected meat of sheep. Humans may occasionally acquire the infection by ingesting food or water contaminated by ova in the excreta of the dog.

We present a case of spinal hydatid disease involving the epidural space without involvement of the vertebral column. The relevant literature is reviewed.

Case Report

A 62-year-old man presented to our institution in August 2003 complaining of severe lumbar pain. According to the patient, he had sought medical treatment for the same symptoms from a general practitioner about 1 month prior. He received reassurance at that point that this was probably not something serious and was advised to rest for 15 days and take NSAIDs. At the time of his admittance to a hospital, there were no neurologie symptoms or signs. There were no bony abnormalities on plain x-rays. Laboratory data including total blood cell count, erythrocyte sedimentation rate, biochemical serum and urine parameters and coagulation tests were normal. CT scan of the lumbar region revealed a minimal disk protrusion at the level of L3-4 and L4-5 and an undefined hypodensity in the right erector spina (Fig. 1). Magnetic resonance imaging of the lumbar spine revealed numerous cystic lesions inside the spinal canal. These lesions appeared isointense on T1- and hyperintense on T2- weighted images and did not enhance after contrast administration. No involvement of the vertebral bodies was evident. On further investigation, the patient gave a history of previous removal of a hydatid cyst located paravertebrally on the right side, at the level of the scapula, as well as of a hydatid cyst of the liver 13 years ago. At this point, we performed an MRI of the entire spinal axis, demonstrating a large number of lesions in the spinal canal, extending from the level of T6 to S1 (Fig. 2). There was no abnormality in the bony vertebral column. The search for systemic disease included MRI of the brain, CT scan of the thorax, CT scan of the abdomen and a bone scan, and revealed a scarred calcified element in the liver and multiple cystic lesions in the upper left and especially upper right lung lobe. Serologic testing for Echinococcus was positive.

Systemic treatment with albendazole 400 mg X 2 was initiated and the surgery was planned within one week. Three days after admittance to our hospital, the patient developed a fever of 39[degrees]C and antibiotic treatment was initiated. One day later, he complained of weakness of his left leg, which within hours evolved to a complete paralysis of his left lower extremity with clinical symptoms of cauda equina syndrome, ie, saddle anesthesia and urination problems. Immediate surgical intervention was undertaken.

Operative Findings

A 2-stage operative procedure was employed. First, a posterior approach was performed. The patient was positioned prone and a longitudinal midline incision was made, extending from T3 to S1. A large cyst (15 X 15 cm) was identified embedded in the paravertebral musculature, on the right side, at the level of T12-L4. The cyst was meticulously removed intact along with the surrounding soft tissue. Posterior decompression with extensive T5-L5 bilateral laminectomies and S1 right-sided hemilaminectomy was performed, which revealed numerous small epidural cysts (Fig. 3). The size of the cysts ranged from a few millimeters to 1.5 cm. The dural sac was markedly displaced anteriorly. A meticulous micro-surgical removal of all of the cysts was followed by extensive irrigation of the surgical area with hypertonic saline (15%) and closure of the wound in anatomic layers. No dural tear was noted during the procedure. Histopathological analysis confirmed the diagnosis of E. granulosus. During the first postoperative days, the lumbar pain and the saddle anesthesia subsided and the patient was able to move his left leg again (muscle strength 3/5). The patient became afebrile postoperatively.

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Two weeks postoperatively, another posterior approach was employed. The patient was positioned prone and a longitudinal midline skin incision extending from T2-S1 was performed. The surgical area was copiously irrigated with hypertonic saline (15%) and the spine was stabilized with pedicle screws and rods using the Monarch System (Depuy-Acromed, Raynham, Mass, USA) from T5 to L5 bilaterally (Fig. 4 and 5). Fusion was performed with matchstick autograft harvested from the iliac crest.

Albendazole was continued for four months. Postoperatively, the patient complained of cramps in the left leg and the motor power in the left leg was 2/5. He was advised to begin physiotherapy. At the last follow-up visit to date, 9 months later, a marked improvement of the muscle strength (4/5) in the affected side was noted, with only sporadic cramps.

Discussion

Spinal hydatid disease, although an infrequent entity of Echinococcal infestation, constitutes an important cause of neurologic disability in endemic countries, accounting for up to 3.8% of spinal cord compression cases in Turkey (9,15) and 14% in Tunisia (5,16-18). In recent years, frequent traveling of people throughout the world, along with massive migration, have resulted in an increasing occurrence of the disease even in nonendemic countries, demanding a high level of alertness from the physician in the western world.

Echinococcosis predominately affects the liver and the lungs, but cysts may develop in various tissues and organs in the body. (5,19) The first description of spinal hydatidosis was made by Churrier in 1807, (5,19,20) almost a century after Bidloo had confirmed the existence of a bony form of the disease. (5) In 1928, Dew (21) introduced a 5-tier classification system for spinal hydatid disease based on the anatomic location of the cyst: 1) intramedullary hydatid cyst; 2) intradural extramedullary hydatid cyst; 3) extradural intraspinal hydatid cyst; 4) hydatid cyst of the vertebra; and 5) paravertebral hydatid cyst. Approximately 90% of spinal hydatidosis cases are located extradurally, most commonly in the vertebral body; (5) from the vertebral column, the infection may then spread into the epidural space or the paravertebral soft tissues. Primary spinal hydatidosis occurs through a hematogenous route. Parasites are considered to reach the highly vascularized center of the vertebral body through the portal vertebral venous shunts. (9,14,22-24) Lodging of the parasites and development of cysts occurs most often in the thoracic spine (49-82%), but the lumbar (18-39%), sacral (2-12.5%) and less frequently, cervical segments may be involved. (2,15,18,19) Secondary disease may occur through direct extension from paravertebral or pulmonary lesions. (5,13,23) Interestingly, our patient had a paravertebral lesion together with multiple epidural lesions from the level of T6 to S1, without evidence of bony involvement. This may indicate the relative resistance of bone to contiguous infection, probably provided by the periosteum and the spinal ligaments. Primary intradural extramedullary hydatid cysts are very rare and most often solitary, (13,25) secondary involvement of the intradural space may result from a ruptured IC cyst and subarachnoid spread of scolices or from a dural tear during operation or lumbar puncture. (5,19,22,26) Intramedullary hydatid disease has also been reported in the literature. (27)

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Spinal hydatidosis, in contrast to the cerebral form of the disease, (28) is predominately seen in adults, usually men 21 to 40 years old. (29,30) Patients most commonly present with a long history (several months to a few years) of back or radicular pain, depending on the exact localization of the cysts. (4,5,20) Lower extremity weakness, paraplegia, sensory deficits, altered deep tendon reflexes, sphincteric dysfunction and cauda equina syndrome are frequently seen in the course of the disease; (5,17) atypical clinical presentations, such as palpable cysts in the soft tissues on either side of the vertebral column, are not seldom encountered. (17,31) Interestingly, in 20% of the cases, (2) symptoms are elicited by trauma. Suspicion should arise in cases of persistent back pain or progressive neurologic signs suggestive of spinal cord compression in endemic countries.

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Definitive diagnosis of hydatid disease remains a histopathological one. Casoni and other serodiagnostic tests are inconclusive, especially in extrahepatic disease, with sensitivity being as low as 25 to 56%. (5) Plain x-rays may reveal the characteristic vertebral "moth eaten" lesions with surrounding sclerosis and calcification of the adjacent soft tissues, which is indicative but not diagnostic of the disease. (5,20) Myelography fails to visualize the extent of the disease into the paravertebral tissues (13) and carries the risk of cyst rupture with subsequent spillage of cyst fluid and dissemination of the disease. (26,32)

CT scan and MRI are the current diagnostic modalities of choice. Irregular bony erosions along with multilocular, non-enhancing "flattened sausage" shaped lesions with very thin, nonseptated walls are the hallmark of vertebral hydatid disease. (1,20,33) In more advanced stages, fragmentation of the vertebral body, the pedicles and the adjacent ribs may be seen. (20,34) Extraosseous lesions are usually unilocular with thicker cystic walls and acquire a spherical shape due to the lack of resistance from the hard bone tissue during their growth; calcifications may develop as the disease progresses. (24) On MRI, the lesions appear isointense to the cerebrospinal fluid (CSF) (hypointense on T1-weighted images and hyperintense on T2-weighted images). (24,33-35) It has been suggested that T2-weighted MRI sequences may be useful in assessing the viability of the cysts; (10,13,25) a decrease in hyperintensity and an increase in the intensity of the cystic wall signal are indicative of a succumbed cyst. MRI is superior to CT scan when there is involvement of soft tissues or neural involvement due to its higher soft tissue resolution and the better delineation of CSF and the spinal cord. (13,24) Concurrent extraspinal infection is commonly reported in up to 46% of cases, (1,2) necessitating further scanning of the head, thorax and abdomen in search for systemic disease. (5)

A number of pathologic conditions may pose difficulties in the diagnosis of spinal hydatid cyst. The most important among them is Pott disease, or tuberculosis of the spine, which closely resembles vertebral hydatid disease. (14,19,36,37) The risk of false diagnosis is particularly high in regions where both tuberculosis and hydatidosis are endemic. Evidence of intervertebral disk involvement, very atypical for echinococcosis, (20,36,38,39) and increased bony reaction, as well as sparing of the pedicles, the posterior arch and the contiguous rib are suggestive of Pott disease. (37) Primary or metastatic, especially lytic, lesions resembling uniloculated, complicated hydatid cysts need to be considered. (14,24,36) Arachnoiditis may be differentiated because of its septations and shape irregularity. (26) Pyogenic or fungal infections, abscesses, fibrous dysplasia and hyperparathyroidism should also be included in the differential diagnosis. (5,14)

Surgical intervention with extirpation of the lesions is the current therapeutic modality of choice. A correct preoperative diagnosis is of paramount importance for the successful planning of surgery. However, in up to 50% of cases, accurate diagnosis is obtained only after surgery. (12) The lack of a defensive reaction from the bone results in a microvesicular infiltrative growth of the hydatid lesions, making in toto surgical removal almost impossible in cases of vertebral involvement. (5,13)

In cases where there is significant spinal cord, cauda equina or nerve root compression by the cysts, posterior decompression and laminectomy should be performed as part of the surgical treatment. This was performed as an emergency in our case because of cauda equina development. In addition, where there is bony involvement, removal of the affected vertebral body along with adjacent healthy tissue through an anterior approach seems to be the most appropriate surgical intervention. (5,12,39) Radical bone resection has been reported to prevent recurrence of the disease, but it has not been proven to prolong survival. (36) The surgical area should always be irrigated with hypertonic saline to reduce the risk of recurrences. (4) Formalin should be avoided due to the risk of toxic myelitis whenever the CNS is involved. (2) Spinal stabilization is indicated for instability either as a result of surgery or as a result of bony destruction by the hydatid cysts. Despite the controversy regarding the necessity of stabilization and fusion after laminectomy, and although there is a risk of spreading the disease into the vertebral body by using pedicle screws, the authors felt that the multiple extensive laminectomies performed for decompression may cause instability. Therefore, we elected to perform stabilization at the second stage. Perioperative rupture of the hydatid lesions carries a great risk of disease dissemination; a carefully planned procedure should therefore be employed. MRI has greatly contributed to a more successful surgical outcome, by delineating the exact anatomic borders of the lesion and its relations to adjacent tissues. Unfortunately, rupture of microvesicles is almost inevitable in cases affecting the bone. (5,13) Recurrence rate in the literature reaches 30 to 40% within the first years after the initial operation. (5,19,20,40) The disease thereafter usually follows a malignant course with multiple recurrences, yielding a median survival of about 5 years (2,41) after the onset of symptoms; Deve therefore named it "cancer blanc" in 1948. (42) Contrariwise, a successful removal of unruptured epidural or intradural cysts can lead to a complete cure. (22) The risk for anaphylactic shock due to spillage of fluid should be taken into consideration. Other surgical complications include secondary bacterial infection, CSF fistula to the skin and neurologic compromise. (15,43,44) Results are considered to be better if early surgery is employed, when focal neurologic symptoms have not yet developed. In cases of recurrence, perioperative mortality may rise to 15%. (17)

Medical treatment with mebendazole, (45) and more recently, albendazole, (43,46) has been advocated to decrease the risk of recurrence in cases of intraoperative cyst rupture or to alleviate the neurologic symptoms by decreasing the size of the lesions in inoperable cases. Praziquantel has been used in combination with albendazole with promising results. (1,17,47) Garcia-Vicuna (43) et al reported a case of a patient with primary solitary echinococcosis of the cervical spine that has remained recurrence-free for 9 years after operation following a cyclic albendazole treatment regimen. Our patient received albendazole 400 mg x 2 for a total period of 4 months. We recommend the use of albendazole for all patients who undergo surgery, regardless of evidence of intraoperative cyst rupture.

Conclusion

Spinal hydatid disease should be considered in the differential diagnosis of spinal cord compression. A high index of suspicion is required even in nonendemic regions of the world, since early intervention and thorough preoperative workup are essential for the treatment of this disease. Although in the vast majority of cases, spinal hydatid cysts are located in the vertebral column, extensive involvement of the epidural space without bone affection may occur. Meticulous surgical extirpation of the lesions and systemic administration of antiheliminthic agents, such as albendazole, are recommended to provide the best outcome for the patients.

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47. Keller TM, Schweitzer JS, Helfend LK, et al. Treatment of Progressive Cervical Spinal Instability Secondary to Hydatid Disease. A case report. Spine 1997;22:915-919.</p> <pre> I'm a great believer in luck, and I find the harder I work, the more I have of it. --Thomas Jefferson </pre> <p>George S. Sapkas, MD, Theofilos G. Machinis, MD, George D. Chloros, MD, Kostas N. Fountas, MD, PHD, George S. Themistocleous, MD, and George Vrettakos, MD

From the First Orthopaedic Department of Athens University School of Medicine, Athens, Greece; the Department of Orthopaedic Surgery, Metropolitan Hospital, Athens, Greece; and the Department of Neurosurgery, The Medical Center of Central Georgia, Mercer University School of Medicine, Macon, GA.

Reprint requests to Kostas N. Fountas, MD, PhD, 840 Pine St. Suite 880 Macon, GA 31201. Email: [e-mail]

Accepted October 24, 2005.

RELATED ARTICLE: Key Points

* Spinal hydatid disease may be a cause of cauda equina syndrome, especially in endemic countries.

* Massive affection of the epidural space without involvement of the vertebral column is possible.

* Removal of cysts in toto is possible when the vertebral bodies are not affected and should be considered the standard of care, along with antiheliminthic agents to decrease the risk of recurrence.