A Typical Low-Back Pain Caused By an Atypical Etiology

By Ergin, Atilla; Toker, Tansel; Yanarates, Omer; Kurt, Ercan; Guzeldemir, M Erdal

Objective: Pain arising in the lumbar spine can have many etiologies, nearly 80% of which cannot be established with certainty. We present a very rare cause of back pain.

Case Report: A 54-year-old woman presented with a 2-month history of low-back pain and right-sided sciatica. Conventional analgesics, physiotherapy, and epidural steroid application had failed to provide relief. She had tenderness of the right sacroiliac joint. Diagnostic fluoroscopic-guided sacroiliac-joint injection with lidocaine did not produce symptomatic relief. Pelvic ultrasonography and magnetic resonance imaging showed septated multilocular hydatic cysts along the sciatic nerve. Surgical exploration noted multicystic lesions along the sciatic nerve woven to the nerve. Her low-back pain disappeared completely after the operation. She received oral albendazole for 6 months to prevent any recurrence of the disease and remains asymptomatic.

Conclusion: Hydatid cyst can be included in the differential diagnosis of lumbar back pain, especially in the endemic areas. Reg Anesth Pain Meet 2007;32:89-92.

Key Words: Low-back pain, Hydatic cysts, Hydateidosis.

Hydatidosis, also known as echinococcosis, has been documented since the time of Hippocrates. Hydatidosis involves several parasitic dis eases that are caused by the larval stages of 4 species of the cestode Echinococcus. These cestodes begin their life cycles in the intestines of definitive hosts, such as dogs, from which they are excreted in feces and subsequently ingested by cattle and sheep (and, rarely, humans), which serve as intermediate hosts. Once ingested, the organism penetrates the intestinal wall of its intermediate host and migrates through the host’s circulatory system, eventually depositing into an organ and forming a cyst. When the intermediate host is eaten by a new definitive host, the cycle repeats. Hydatidosis has a characteristic geographic distribution with a high prevalence in sheep-raising and cattle-raising regions.1,2 It is rarely reported in developed countries, except when it is imported from endemic areas.

In humans, Echinococcus granulosus most commonly deposits itelf in the liver (55% to 70%), lungs (18% to 35%), or uncommon locations such as the brain, bones, muscles, adrenals, and the as the brain, bones, muscles, adrenals, and present with many different clinical symptoms that generally result from enlarging cysts. Cyst leakage or rupture carries the potential risk of triggering severe allergic reactions to parasite antigens. Diagnosis of a cyst on a peripheral nerve is very rare; symptoms are often absent and, in many cases, cysts are only discovered accidentally by imaging studies. This case report describes a rare instance of a hydatid cyst that caused severe and progressive low-back pain (LBP) with associated neurologic dysfunction.

Case Report

A 54-year-old woman presented with a 2-month history of LBP and pain radiating down her right sciatic nerve. The pain was associated with numbness and weakness in her right leg and foot. Primary-care practitioners concluded that her systoms were caused by nerve-root irritation. Despite conservative treatment, she did not obtain relief from her symptoms.

A physiatrist performed lumbar epidural steroid injection, but 2 weeks later, the severity of her pain had increased and new diminished sensation on the right L4 to L5 dermatomes was noted. Magnetic resonance imaging (MRI) study showed bulging of the L4-L5 intervertebral disc and that was felt not to be producing nerve- root pressure.

The patient was then sent to our pain clinic for consultation. The patient exhibited right paravertebral muscle spasm with tenderness over her right sacrum and sacroiliac joint. Lumbar spinal movements were painful; the pain radiated to her right buttock, posterolateral thigh, and calf and could be reproduced with sciatic- nerve stretching. Neurologic examination revealed 4/5 quadriceps weakness when, as well as decreased sensation in the right L4-L5 dermatomes. Her right ankle reflex was decreased. Anal reflex and anal sphincter tone were normal.

Diagnostic fluoroscopy by use of a 2-mL 2% lidocaine injection into the left anteroinferior sacroiliac joint did not relieve the symptoms. Pelvic ultrasonography (US) revealed septated multilocular hyperechogenic cysts situated in the pelvic inlet along the sciatic nerve. Pelvic MRI also revealed septated multiloculoar cysts in the presacral region (Fig 1). Ultrasound of the liver and spleen were normal. A Casoni test,6 used to diagnose hydatidosis, was negative, but because Casoni tests may yield false-negative results, an indirect hemagglutination (IHA) test7 was performed. The IHA test result was also negative. No indication of the primary source of the infestation by E. granulosus was evident after chest radiography and computerized tomography (CT) of the thorax, abdomen, and head.

Fig 1. Right posterior fat sat-T2 weighted coronal MRI shows multilocular biseptated lesion along the sciatic nerve. (1) Multilocular, septated cyct hydatic; (2) sacral vertebrae; (3) rectum; (4) pelvic muscles.

Fig 2. Exisional hydatic cyst.

The patient underwent explorative surgery, during which surgeons found a multilocular lesion (Fig 2) intertwined with the sciatic nerve. The patient’s LBP improved dramatically within 24 hours. She was given twice daily oral albendazole 200 mg for 6 months, an antiparasitic medication from the benzimidazole family to prevent disease recurrence. The patient is still asymptomatic at the time of this report.

Discussion

Hydatid disease is caused by infection with tapeworm larvae (metacestodes) from the genus Echinococcus. Within the genus, 4 species are recognized: E. granulosus, which causes cystic hydatid disease; E. multilocularis, which causes alveolar hydatid disease; and E. vogelii and E. oligarthrus, both of which cause polycystic hydatid disease. E. granulosus has at least 6 genetically distinct strains, 2 of which are involved with human infection. The sylvan strain propagates in wolves and wild ungulates in Northern Alaska, Canada, Scandinavia, and Eurasia. The pastoral strain propogates in dogs and domestic ungulates throughout the world. Most human infections are caused by the pastoral strain. Endemic regions of human cystic hydatid disease include the southern parts of South America (Uruguay and Argentina), the Mediterranean region, the Middle East, many parts of Africa (especially Kenya), Southern and Central Russia, Central Asia, and many regions in China (especially the Xinjiang Province). The majority of reported patients in Austria, Germany, and Switzerland are immigrants from the Mediterranean region. In the United States, most infections are seen in immigrants from endemic areas, but transmission has been noted in Alaska, California, Utah, Arizona, and New Mexico. Hydatid cysts are most commonly found on the right lobe of the liver (75%), but may affect other organs such as the lungs (2% to 5%), muscles (5%), brain (5%), spleen (2% to 5%), kidneys (2%), heart (1%), pancreas (1%), and central nervous system (1%).8 Manifestation of the disease depends on the location and size of the hydatid cyst.8 The occurrence of hydatidosis in soft tissues is very rare, and its epidemiology has not been welldocumented. In humans, hydatidosis may be serious, with a reported mortality of 4%, usually caused by anaphylactic shock from cyst rupture.9

In our case, sacroiliac disease as a source of the patient’s complaints was eliminated by a negative anteroinferior sacroiliac- joint injection. The necessity of performing sacroiliac injections after pelvic US is controversial. In this case, accidental cyst puncture and subsequent rupture leading to anaphylaxis could have been catastrophic.

Physicians should consider hydatid disease in the differential diagnosis of cystic lesions, particularly in endemic areas. Human hydatidosis still poses a significant public-health problem, especially in countries with a migrant population from endemic areas. The lack of specific prophylactic measures and the latency of the disease may hinder its eradication from the human population. Prophylaxis is more effective than treatment. Elimination of the disease can only be achieved by breaking the life cycle of the parasite among its hosts through implementation of preventative measures.

The most important factor in the diagnosis of pelvic hydatid disease is an awareness of its possibility. Clinicians usually reach the diagnosis of hydatid disease on the basis of imaging studies such as US, CT, and MRI. Imaging examinations should be confirmed by serologic tests, which are 80% to 100% sensitive and 88% to 96% specific for liver hydatid disease but are less sensitive for lung and other organ involvement. Therefore, US should be the first line of screening for abdominal and pelvic hydatidosis.3 The sonographic analysis of the morphology and structure of the cyst is thought to correspond to evolutionary stage of the hydatid cysts.10 In our case, we determined the cysts as type III (fluid collection with septa), according to Gharbi’s classification.

Before surgical excision or biopsy and extirpation of a cyst, diagnosis of hydatidosis should be excluded to avoid leakage of cyst contents and the accompanying risks of anaphylaxis. Preoperative diagnosis of musculoskel\etal E. granuhsus infection is difficult, both clinically and radiologically. It may resemble any soft-tissue tumor. Garcia-Diez reported MRI examinations of 7 patients with musculoskeletal hydatidosis. Typical signs of hydatidosis were multivesicular lesions with or without a hypointense peripheral ring (rim sign). According to the presence of viable daughter cysts, the MRI findings are high signal intensity or low signal intensity on T2- weighted images.11 Proton density-weighted images generated by gradient echo sequences as a sign of biological activity were suggested by Tekkok et al.12

Surgical excision of the cyst remains the treatment of choice. Removal of the main cyst mass, however, may not be effective because a small daughter cyst can be left behind.9 Chemotherapy and percutaneous treatments are widely available. Several reports have shown that the use of mebendazole often results in cestode death and shrinkage of the cyst, thereby avoiding the need for surgical intervention. Albendazole, an absorbable derivative of mebendazole, shows even greater effectivenes, because it has a higher degree of penetration into the cyst and is particularly indicated for reducing the risk of recurrence.13-14 The medication should be given during the preoperative and postoperative periods to decrease the chance of anaphylaxis, decrease the tension in the cyst wall, and reduce the postoperative recurrence rate.

In conclusion, hydatid cyst should be considered in the differential diagnosis of LBP, especially when treating patients in or from areas where E. granulosus is prevalent.

References

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13. Bartloni C, Tricerri A, Guidi L, Gambassi G. The efficacy of chemotherapy with mebendazole in human cystic echinococcosis: Long term follow up of 52 patients. Ann Trop Med Parasitai 1992;86:32493256.

14. Teggi A, Lastilla MG, De Rosa F. Therapy of human hydatid disease with mebendazole and albendazole. Antimiaob Agents Chemother 1993;37:1679-1684.

Atilla Ergin, M.D., Tansel Toker, M.D., Omer Yanarates, M.D., Ercan Kurt, M.D., and M. Erdal Guzeldemir, M.D.

From the Gulhane Military Medical Faculty, Department of Anesthesiology and Reanimation, Ankara, Turkey.

Accepted for publication September 14, 2006.

Reprint requests: Atilla Ergin, M.D., GATA Medical Faculty, Department of Anaesthesiology and Reanimation, 06018 Etlik, Ankara, Turkey. E-mail: aergin@gata.edu.tr

2007 by the American Society of Regional Anesthesia and Pain Medicine.

1098-7339/07/3201-0001$32.00/0

doi:10.1016/j.rapm.2006.09.008

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