Spinal hydatid disease.

As the title of the article by Sapkas et al indicates, spinal hydatid disease is rare and very few physicians will encounter this condition in North America. However, two strains of Echinococcus granulosus are endemic in animals in North America. The cervid strain is prevalent in the holarctic zones of the tundra and boreal forests of Alaska and Canada, while the sheep strain occurs sporadically in parts of Utah, Arizona, New Mexico, California and other western states. (1) Hydatid disease is not a reportable disease in the United States, so the extent of its prevalence is not known. Historically, the majority of patients diagnosed with the sheep strain of E. granulosus in the USA have been immigrants, who acquired the infection in their counties of origin. Until 1970, the majority of patients were of Italian and Greek origin, whereas in recent decades, patients from the Middle Eastern and South American countries have been the majority. (2,3) Indigenous infections occur sporadically in the north and in other parts of the USA, mainly in populations at relatively high risk, such as sheep farmers in endemic areas. It would be of interest to know whether the patient in the case reported was an immigrant, whether the infection was acquired in the US and whether there were any risk factors.

Recommendations for treatment of rare conditions cannot benefit from randomized controlled trials or cohort studies, and one will have to depend on case series and occasionally, only on case reports. It is abundantly clear from the many case series and reports that the outcome of posterior decompression and laminectomy for intraosseous spinal hydatid disease is poor. Historically, when spinal metastases were similarly treated with posterior decompression and laminectomy, the outcome was similarly poor. Thereafter, posterior surgery was mostly abandoned and anterior surgery was advocated. However, since the development of rigid posterior fixation devices, the majority of surgery for spinal metastasis is now performed with posterior decompression and stabilization, although anterior surgery still has its indications and proponents. A similar trend has occurred with surgery for spinal hydatidosis. So far, there is only limited evidence that the surgical outcome in spinal hydatidosis has improved with the use of stabilization devices or using combined anterior and posterior surgery. (4,5)

As the authors point out, intramedullary, intradural extramedullary, and only extradural disease, without involvement of the vertebral body, such as the case presented, are all rare. In such cases, the bones are not affected and the only bone that needs to be removed is that necessary to expose the spinal cord, nerve roots and the hydatid cysts. Although there are some controversies regarding the indications for stabilization and fusion, if only partial or complete laminectomy without excessive facet joints excision is performed, no fusion or stabilization is recommended. The authors felt that instability may occur with the extensive posterior laminectomies, and therefore stabilization was necessary. Obviously, instrumented fusion from T2 to L5 is major surgery with serious risks of blood loss, wound and neurologic complications. It must be clear that whereas spinal decompression and excision of the cysts is absolutely necessary in most such cases, the decision to add instrumented fusion depends on whether instability is already present or created by the necessary surgical decompression.

If stabilization with pedicle screws is performed, the surgeon should be aware that theoretically the disease may be iatrogenically seeded into the vertebral bodies if viable scolices are present at the time when the pedicles are probed before inserting the screws. The authors should be congratulated on their meticulous decompression and well-performed instrumented fusion.

The diagnosis is frequently made during or after surgery, (4) but fortunately in the case presented, the diagnosis was suspected preoperatively as the patient had previous surgeries for hydatid cysts. This article is a reminder that surgeons should pre- and intraoperatively keep an open mind regarding the many causes of spinal cord compression including rare infections, such as Hydatidosis.

The authors review the diagnosis and treatment of spinal hydatid disease. However, as the seriousness of this condition is clear, it is obvious that control or eradication of the disease, as has occurred in islands such as New Zealand and Tasmania, or measures of prevention of the disease, (1) would be much more effective than treatment.

References

1. Eckert J, Schantz PM, Gasser RB, et al. Geographic distribution and prevalence. In EckertJ, Gemmell MA, Meslin F-X, Pawlowski ZS (eds): WHO/OIE Manual on Echinococcosisin humans and animals: a public health problem of global concern, 2001. Available at: http://whqlibdoc.who.int/publications/2001/929044522X.pdf.

2. Rao S, Parikh S, Kerr R. Echinococcal infestation of the spine in North America. Clin Orthop 1991;271:164-169.

3. Donovan SM, Mickiewicz N, Meyer RD, et al. Imported echinococossis in southern California. Am J Trop Med Hyg 1995;53:668-671.

4. Pamir MN, Ozduman K, Elmeci I. Spinal hydatid disease. Spinal cord 2002;40:153-160.

5. Karray S, Zlitini M, Fowles JV, et al. Vertebral Hydatidosis and paraplegia. J Bone Joint Surg 1990;72:84-88.

Rabi M. Khazim, MD, MPH, FRCSC 

From the Southend Hospital Westcliff on Sea, Essex, United Kingdom.

Reprint requests to Rabi M. Khazim, MD, MPH, FRCSC, Southend Hospital Westcliff on Sea, Essex, England SS0 0RY. Email: rkhazim.hotmail.com

Accepted October 10, 2005.