Intradural extramedullary spinal hydatidosis: case report

Hidatidosis espinal intradural extramedular: presentación de un caso

A. Kaen; A. Lagares; A. Perez-Nuñez; J.J. Rivas; A. Ramos* and R.D. Lobato

Department of Neurosurgery and Neuroradiology*. Hospital 12 de Octubre. Madrid. Spain.

Correspondence

The parasitic tapeworm Echinococcus granulosis causes hydatid disease, which is rarely encountered in nonendemic regions. It is a progressive disease with serious morbidity risks. Rarely, these cysts are found in the spine. They are mainly found epidurally, originating from direct extension from pulmonary, abdominal or pelvic infestation. Nevertheless, the main mechanism for intradural involvement is not yet clear. Antihelminthic treatment should be administered for a long period following early decompressive surgery. We report a case of recurrent hydatid disease that presented unusual intradural dissemination. Prognosis for spinal hydatid disease remains very poor and comparable to that of a malignant neoplasm.

Key words: Hydatid cysts. Intradural. Spine. Echinococcus.

RESUMEN

El Equinococcus granulosis es el parásito causante de la hidatidosis, que se encuentra de forma muy poco frecuente en regiones no endémicas. Es una enfermedad quística progresiva con riesgo de causar morbilidad importante, afectando principalmente al hígado y al pulmón. Muy raramente se encuentran quistes a nivel espinal. La hidatidosis espinal afecta sobre todo al espacio epidural por extensión directa de infección existente a nivel pulmonar, abdominal o pélvico. No obstante, el mecanismo para la afectación intradural todavía no está aclarado. El tratamiento antihelmíntico ha de ser administrado durante largo tiempo tras la cirugía descompresiva. Presentamos el caso de una hidatidosis espinal recurrente que presentó una diseminación intradural inusual. El pronóstico de la hidatidosis espinal continúa siendo muy pobre, comparable al de una enfermedad neoplásica maligna.

Palabras clave: Hidatidosis. Intradural. Espinal. Echinococcus.

Introduction

Hydatid disease is caused by the larval form of Echinococcus granulosis and the most common form of presentation is by lung and liver cysts. Spinal hidatidosis is extremely⁶rare and cysts are most frequently located at the epidural level, originating from direct extension from pulmonary, abdominal or pelvic infestation². Although the standard treatment is total surgical removal of the cysts without inducing any spillage, it not may be possible to perform this in patients with multiple and fragile cysts. In such cases, the neural structures should be satisfactorily decompressed and albendazole should be administered promptly. However, the success in the treatment of vertebral hydatidosis represents a challenge due to its invasive nature; consequently its poor prognosis has been compared with that of malignant spinal tumor. We report the case of a patient with recurrent hydatid disease who had an unusual intradural dissemination without cerebral involvement.

This 59-year-old man consulted because of back pain and progressive difficulty in walking. He had been both pharmacologically (the patient received mebendazole 40 mg/kg) and surgically treated for more than twenty years for recurrent hydatid disease affecting the lungs and liver. One year before admission he had been implanted a lumbar catheter for infusion of opioids, but it was removed because of poor analgesic response. His pain had progressively increased for 4 months. Physical examination showed local tenderness at the middle and lower thoracic regions, bilateral lower extremity weakness (4/5), bilateral Babinski sign, and hypoesthesia below T6. Bowel and bladder functions were intact. A MR of the thoracic and lumbar spine revealed several multiloculated non calcified cysts in the spinal canal which were clustered at two levels; some located at T6 in connection with intrathoracic hydatid infestation which protruded into the canal through the destroyed right T6 pedicle an apparently extradural; others at T10 and T12 level seemed extradural too (fig. 1). Routine laboratory results were normal with the exception of a high erythrocyte sedimentation rate. With the diagnosis of epidural spinal hidatydosis he was operated on performing a T5-T6 and T9-T12 laminectomy. Although cystic lesions that had been found at T6 were extradural and connected to those present in the chest, no epidural lesions were found at T9-T12 level. To prevent the disease spreading intraduraly the operation was terminated and a control MR confirmed the intradural presence of hydatid cysts. The surgical field was irrigated with hypertonic saline (20%) and povidone iodine. Histopathological examinations confirmed hydatid disease.

Figure 1. MR images demonstrate thoracic hydatid
cysts that extend through the right T6 neural foramen
into the vertebral canal compressing the cord (A and B);
and another group of cysts at T10-T12 that were
erroneously diagnosed as extradural disease (C).
Sagittal T2-weighted image of the thoracic spine (D)
shows several multiloculated cysts (white arrows).

Figure 3. Intraoperative photograph showing multiple intradural cysts (A)
covered by a thick arachnoid reaction, displacing and distorting the
roots of the cauda equine. Thereafter, a durotomy was performed (B and C), 
and hydatid cysts were carefully removed between lumbo-sacral nerves (E).

The patient had to be readmitted three months later because he reported that he had suffered several falls in the last week. He also complained of pain in the lower extremities without a clear radicular pattern, increasing instability 3/5 motor strength in both legs. A spinal MR showed recurrent intradural hydatid disease in the thoracic and lumbar spine with the development of new intradural lesions from C6 to T4, which posteriorly compressed the spinal cord. These new cervical lesions were operated on through a C5T4 laminectomy, but despite the evacuation of these cysts, the patient's neurological condition gradually worsened and three weeks after the operation he remained paraplegic with a T10 sensory level and new multiple intradural cysts below the level of the last surgery.

Hydatidosis is caused by two larval forms of Echinococcus, E. granulosus and less commonly E. multilocularis. The most common site of infection is the liver (74% of the cases) and lungs (15% of the cases)². This disease is extremely uncommon in developed countries, like North America and Europe, and more frequent in countries with poor socio-sanitary conditions¹⁹.

Infection of the central nervous system is unusual, and only between 2 and 4% of the patients with hydatid disease present brain cysts^10,18. Bone involvement occurs in 1% of the patients, and approximately half of them show spinal involvement. Any segment of the spine can be affected, including the thoracic (50%), lumbar (20%), sacral (20%) and cervical (10%) regions^7,8. These segments can be affected by an isolated or by multiple cysts. Infestation may occur at any location, primarily or by metastatic seeding of protoscolices released from another location.

The clinical presentation of spinal hydatidosis is variable, including paraparesis (62%) or paraplegia (26%), back pain or radicular pain (55%), numbness or sensitivity loss (36%) and sphincter disturbance (30%)². Morphologically, spinal involvement has been classified by Braithwaite and Lees⁵ (Figure 4) into five types: 1) Primary intramedullary hydatid cysts; 2) Intradural extramedullary hydatid cysts; 3) Extradural intraspinal hydatid cysts; 4) Vertebral hydatidosis; and 5) Paravertebral hydatidosis. The intradural and extramedullary involment, like our case, is extremely rare^{1,4,9,10,13,14,16}, especially in non-endemic countries.

Figure 4. Braithwaite and Lees classification.

Diagnosis has been improved with the use of MR.

Hydatid cysts have an unique appearance on MR. On T1weighted images viable cysts appear to contain a low intensity fluid surrounded by an iso- to mildly hyperintense wall which on T2-weighted images appears as a low-intensity rim surrounding the high signal cyst content. The appearance of the cysts on T2-weighted images indicate their viability, as a decrease in the intensity of the signal of the content and an increase of the signal of the cyst walls indicate a dying cyst¹⁷.

One of the main points regarding our case is the occurrence of intradural extramedullary spinal hydatidosis without macroscopic involvement of the brain. In our case the initial spinal hidatidosis spread to the intradural space, so he deteriorated from type III to type II of Braithwaite and Lees classification⁵. The route of spread of the disease to the spine is still not fully determined. Spinal hydatidosis usually begins in the marrow of a vertebral body and may progress around the neural arch, through adjacent ribs, reaching the spinal canal or the intervertebral discs; thus spinal involvement is believed to occur through vertebral-portal venous anastomosis¹⁹. In addition, extradural disease may spread through the neural foramen into the surrounding soft tissues as in the initial upper thoracic involvement in our case. However, the main mechanism for the intradural extramedullary involvement is not yet clear. Primary hematic dissemination is regarded as the most plausible mechanism², but dural tearing during surgery or during an aggressive invasion of spinal space, like lumbar puncture, may have a role in the etiology of the spreading of the infestation into the intradural space. This mechanism is well known for bacterial dissemination, but not for parasite spread¹². Although in our case there was such an antecedent, the dural puncture was located far away from the initial side of infestation. Moreover, during the first surgery we were not able to detect any dural defect. Therefore, the most plausible mechanism of the intradural spread of the disease in our case is hematic dissemination.

Pharmacological treatment of hydatid disease, especially when combined with surgical treatment, has reached some degree of success¹³. Albendazole and mebendazole are the main anti-helmintic drugs used. Nevertheless, bony involvement has demonstrated a less favorable response than other sites³.

Despite the increasing use of surgical and medical treatment, prognosis for spinal hydatid disease remains very poor and it is comparable to that of a malignant neoplasm.

References

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Correspondence:
Ariel Kaen. ]]> Servicio de Neurocirugía.
Hospital 12 de Octubre.
Avda. Córdoba s/n.
28041. Madrid. Spain.

Recibido: 12-03-08.
Aceptado: 1-09-08.

Comentario al trabajo Intradural extramedullar spinal hydatidosis: case report de Ariel Kaen y cols.

Los autores Ariel Kaen y cols., presentan un caso de hidatidosis espinal con diseminación intraespinal tras la cirugía, con un pronóstico funcional fatal. Parasitosis como la hidatidosis o la neurocistiercosis suponen en la actualidad un grave problema de salud pública en países subdesarrollados donde esta enfermedad es endémica. Las fuertes corrientes migratorias así como el acceso constante de viajeros de nuestros países a dichas zonas han sido responsables de la reaparición de la citada patología en nuestros hospitales. La hidatidosis suele afectar a la columna vertebral en menos de un 1% de los casos. El tratamiento quirúrgico realizado por los autores suele ser el indicado en la literatura; aunque el tratamiento de elección es la exéresis total de los quistes, muchas veces el neurocirujano tiene que conformarse con realizar una descompresión del canal espinal. Es fundamental no romper los quistes durante la cirugía para evitar la diseminación de la enfermedad, en este aspecto, maniobras como la irrigación con suero salino hipertónico son de dudosa eficacia. Es mandatario el tratamiento con albenzadol durante un periodo mínimo de 3-4 meses. Los autores recogen una afirmación de la literatura donde comparan el pronóstico final de la enfermedad con una neoplasia maligna. En nuestra experiencia, encontramos algún caso de hidatidosis pulmonar con invasión espinal en los que hemos conseguido mediante descompresión y tratamiento el control de la enfermedad durante varios años. En este tipo de casos donde el riesgo de rotura de las vesículas es alto (cercano al 44%) y la recurrencia de la enfermedad es del 30 al 100%, a veces sería preferible adoptar posturas menos agresivas y realizar descompresión y tratamiento médico.

J. Enseñat Nora