Neurosurg Focus 17 (6):E8, 2004
Recurrent spinal hydatidosis in North America
Case report and review of the literature
GREGORY D. SCHNEPPER, B.S., AND WALTER D. JOHNSON, M.D.
Division of Neurosurgery, Loma Linda University, Loma Linda, California
Spinal hydatidosis is an uncommon manifestation of the parasite Echinococcus, affecting fewer than 1% of patients
with hydatid disease. The authors report on a 34-year-old Turkish woman who presented with recurrent primary spinal
hydatid disease. The patient originally presented with progressive numbness and paraparesis that was reversed after
T5–6 laminectomy and cyst removal. Pathological findings indicated parasitic infection and she underwent treatment
for cysticercosis. Nevertheless, she returned 4 years later with back pain, numbness, and monoparesis. Neuroimaging
studies revealed spinal cord compression with multiple cysts that were again resected. Pathological findings were consistent with Echinococcus.
Although this disease is uncommon, particularly in North America, the authors conclude that spinal hydatidosis
should be considered in the differential diagnosis of any patient who has lived or traveled within endemic areas and
who presents with spine lesions and cord compression. The authors review the literature pertaining to the epidemiological features, presentation, diagnosis, neuroimaging characteristics, recommended treatments, and overall prognosis of spinal hydatidosis.
KEY WORDS • hydatid cyst • Echinococcus • spinal infection • myelopathy
Hydatidosis affecting the spine comprises less than 1%
of the total cases of hydatid disease and is particularly uncommon in North America. Often the diagnosis is difficult
to make by either neuroimaging or immunohistochemical
modalities, yet successful management relies on precise
diagnosis in combination with appropriate and thorough
treatment. Without this combination, recurrence is generally predictable. We report such a case of recurrent hydatid disease of the thoracic spine, which was partly due
to misdiagnosis and, consequently, inadequate treatment.
CASE REPORT
History and Examination. This 34-year-old Turkish
woman presented on March 21, 2000, with a 4-month history of tingling in both feet, numbness from her waist to
her ankles, and bilateral lower-extremity weakness. She
reported back pain, a burning sensation in her hips, and
sore calf muscles. On examination, she had mild paraparesis with a sensory level at T-5 as well as tenderness at
that level, 1 bilateral patellar and Achilles reflexes, and
an unsteady gait.
Neuroimaging. Admission MR imaging demonstrated
an epidural mass at T-5 that was projecting 1.5 cm into the
spinal canal and eroding the left pedicle and portions of
Abbreviations used in this paper: CT = computerized tomography; MR = magnetic resonance.
Neurosurg. Focus / Volume 17 / December, 2004
the body, lamina, and proximal T-5 rib head (Figs. 1 and
2). At least five separate cystic areas were evident. The
principal working diagnosis was spinal cord tumor.
Operation and Subsequent Treatment. Surgery involved a thoracic laminectomy of T5–6 and resection of
the tumor, with spinal cord and T-5 nerve root decompression. The surgical specimen measured 1.5 2 cm and
was described as a whitish, pearllike, semitranslucent,
cystic material, which was thought to be parasitic. Results
of pathological testing were not definitive, but indicated
there were features of hydatid cyst (Echinococcus granulosus), or cysticercosis. The decision made at that time
was to treat her according to the presumed diagnosis of
cysticercosis.
Repeated Presentation and Examination. The patient
returned in early 2004; her chief symptom was back pain
that had continued for 3 months, associated with numbness in her left breast, axilla, and bilateral lower extremities. Clinical findings included 4/5 motor strength in the
right lower extremity causing a limping gait. She had a
limited range of motion because of pain.
Findings on Repeated Neuroimaging. On repeated MR
imaging and CT scanning, a 3.8 1.8 3–cm multiloculated cystic structure was demonstrated at the T4–5 levels
(Figs. 3 and 4). The preoperative diagnosis was an epidural paracystic mass at T-5.
Second Operation and Postoperative Course. Surgery
involved an extracavitary approach with excision of the
1
G. D. Schnepper and W. D. Johnson
Fig. 1. Sagittal precontrast (left) and postcontrast (right) T1weighted MR images demonstrating a large, minimally enhancing
mass with spinal cord compression at T-5.
head of the fifth rib and the transverse process for resection of the epidural mass at T-5. The mass was composed
of multiple cysts of varying sizes containing scolices (Fig.
5). Postoperatively, the patient was able to move all four
extremities well. When she was discharged home in 7
days, she was ambulatory and had complete resolution
of her numbness. Her discharge diagnosis was spinal hydatidosis consistent with Echinococcus. Her follow-up
visits have been routine, with no recurrence of her symptoms; she is being followed closely in the Infectious Disease Clinic. She is currently receiving a minimum 6month course of albendazole.
DISCUSSION
Hydatid disease is caused by two forms of the parasite
Echinococcus: E. granulosus, and less commonly E. multilocularis, the latter primarily causing alveolar echino-
Fig. 2. Sagittal T2-weighted MR images highlighting cyst fluid
and spinal cord compression.
2
coccosis. Bidloo9 first reported osseous hydatidosis in
1708, in a case involving the humerus. In 1807, Chaussier14 reported the first case of spinal hydatid disease, and
Reydellet34 is believed to have performed the first surgical
intervention for spinal hydatidosis in 1819. Lloyd26 reported the first North American case of vertebral hydatidosis
in 1896.
The definitive hosts of Echinococcus are dogs, wolves,
and other carnivorous animals, in which the adult parasite
lives within the intestine and the ova are subsequently
passed in the stool. Intermediate hosts, such as sheep, cattle, horses, and hogs, ingest the ova, which then hatch into
embryos (hexacanth) in the duodenum. The embryos reproduce asexually and form multiloculated cysts. Humans
contract the disease by contamination through direct contact with the definitive host or its feces, or by ingesting
food infected with ova.3,48
The parasite is most commonly found in livestock-raising areas in Mediterranean countries, Africa, South America, New Zealand, and Southern Australia,42 but has a
worldwide distribution. Although rare in North America,
cases have been reported in California, Utah, the Lower Mississippi valley, Alaska, and northwest Canada.36
In countries where the disease is endemic, it is a major
public health concern, a fact reflected by the 21,303 cases
of hydatid disease reported between 1987 and 1994 in
Turkey.4
The most common sites of infection are the liver (75%),
lungs (15%), and brain (2–4%).20,35,42 Bone involvement is
uncommon, but when present it affects the vertebrae 44%
of the time.5 In total, however, only 0.5 to 1% of hydatid
disease cases involve the spine.13 Vertebral hydatid disease
is more likely to be caused by a primary process than a
secondary one, although there have been case reports of
local spinal invasion from pulmonary hydatidosis.21,40
Spinal involvement has been classified by Braithwaite and
Lees10 into five types: 1) primary intramedullary hydatid
cyst; 2) intradural extramedullary hydatid cyst; 3) extradural intraspinal hydatid cyst; 4) hydatid disease of the
vertebrae; and 5) paravertebral hydatid disease. Of these
five, the first three types are considered rare. In our review
of 232 reported cases, the vertebral level involved was
documented in only 129 patients, establishing thoracic involvement as the most common level (52%), followed by
lumbar (37%), and then cervical and sacral involvement
(5.5% each). There was one case of thoracic involvement
stemming from the seventh rib.
Spinal involvement is believed to occur through vertebral–portal venous anastomosis.21 Infestation of the spine
is described to progress as a multivesicular infiltration of
cancellous bone that involves the vertebral bodies, pedicles, and laminae to varying extents.47 The intervertebral
discs, however, are usually spared because the cyst growth
is confined within the periosteum.46
Histologically, E. granulosus can be identified by its
multilayered cyst wall containing hooklet-bearing scolices. The thick outer laminated wall may calcify and is
composed of layers of chitin.43 The innermost germinal
layer produces hydatid fluid and may contain numerous
embryonal scolices termed “hydatid sand.”
A review of reported cases of spinal hydatidosis reveals
a greater rate of infection in men (62%) than in women
Neurosurg. Focus / Volume 17 / December, 2004
Recurrent spinal hydatidosis in North America
Fig. 3. Axial T2-weighted MR images demonstrating a multiloculated cystic structure with spinal cord compression.
(38%). The patients’ age ranged from 6 to 74 years, with
a mean age of 36 years. This disease is found primarily in
adults because of its slow progression; however, cases in
children have been reported. The most common signs and
symptoms include paraparesis (62%) or paraplegia (26%),
back or radicular pain (55%), sensory loss or disturbance
(36%), and sphincter disturbance (30%).
Diagnosis is usually difficult, and often is not made
Fig. 4. Sagittal T2-weighted MR images revealing recurrence of the cysts.
Neurosurg. Focus / Volume 17 / December, 2004
3
G. D. Schnepper and W. D. Johnson
Fig. 5. Photomicrograph showing a scolex.
until clinical signs and symptoms of spinal cord or nerve
compression appear. Even then, spinal hydatidosis is often
misdiagnosed. The differential diagnosis for vertebral hydatid disease includes Pott disease, syphilis, bacterial and
fungal osteomyelitis, osseous angioma, chordoma, sarcoma, and hyperparathyroidism.12 There is little documented
success with the use of serological or skin tests as diagnostic tools,13,32 but immunochemical and molecular techniques have been used to confirm the diagnosis.11 Use of
indirect hemagglutination or the enzyme-linked immunosorbent assay to detect serum levels of Echinococcus may
be helpful for preoperative diagnosis.37 Although diagnosis may be difficult, the best approach probably consists of
a detailed history and clinical evaluation of the patient
combined with precise neuroimaging.
The neuroimaging methods of choice are CT scanning
and MR imaging. Plain x-ray films are nonspecific and
may fail to show changes in the spongy bone related to
initial multivesicular infiltration.31 Myelography, now
mostly replaced by MR imaging, is considered invasive
and can be dangerous because of possible dissemination
of the disease intradurally; it is also limiting because it only shows the mass effect on the dural sac.50
The CT scanning modality is useful for clearly demonstrating destructive bone changes and paraspinal soft-tissue involvement.2 It has an advantage over MR imaging in
demonstrating subtle osteolytic changes,31 but CT scanning is limiting because it cannot be used to distinguish
between cystic lesions and the dural sac.16 Multiple cysts
create additional difficulties, because larger cysts may disguise smaller ones. The CT modality is most useful combined with either MR imaging or myelography.
Magnetic resonance imaging is the best single neuroimaging modality for precise determination of the anatomical relationship of the cystic lesions and their exact
level, as well as allowing imaging of the entire neuraxis.6
Fahl, et al.,16 have described the characteristics of hydatid cysts on MR images, reporting that cysts generally
have two dome-shaped ends, have no debris in the lumen,
and usually look like flattened sausages, with thin, regular
walls without septations. Intradural cysts may be single or
multiple; extradural cysts are always multiple and involve
4
the bone. The T1-weighted MR images are particularly
sensitive for identifying cystic lesions and their relationships to surrounding structures. Tekkok and Benli,45 using
proton density–weighted images, were able to characterize a viable cyst as one containing low-intensity fluid with
iso- to mildly hyperintense cyst walls. A dead cyst was
identified by a decrease in hyperintensity and an increase
in hypointensity from collapsed cyst walls. Postoperative
MR imaging is invaluable for determining the completeness of resection as well as for documenting any recurrent
or newly developing cysts.
Surgery is the most common initial treatment for hydatid disease, with total removal of the cyst(s) the primary
goal.23,29,30 For spinal hydatidosis, laminectomy with simple decompression is used most frequently, yet it is not
without accompanying risks. Complications often arise
due to excessive local mass effect on critical neural structures, combined with a cyst growth rate of up to 7 mm per
month.3 Also, the cyst’s thin walls may easily rupture,
either spontaneously or due to trauma or surgery, resulting
in recurrence of multiple cysts, or the development of
an anaphylactic reaction secondary to contact with intracystic fluid.3,28 Rupture occurs most frequently in spinal
hydatidosis because the cysts are contained in narrow
spaces within bone boundaries, making removal particularly difficult. Rupture rates have been reported to be as
high as 44.4%, particularly if the cyst is in an extradural
location.3 No specific surgical technique has been found to
avoid this problem completely, although the operating microscope can be helpful.
Chemotherapy is often used in conjunction with surgery
to prevent recurrence and to protect the patient from dissemination of a ruptured cyst. Albendazole and mebendazole are the two most commonly used anthelmintic drugs.
Studies have indicated that albendazole is more effective
because it is better absorbed and has increased efficacy.27,44
Albendazole acts by blocking glucose uptake and depleting the glycogen stores of the parasite.38 No long-term
studies have documented potential side effects of albendazole or mebendazole, although albendazole may cause a
temporary, minor elevation in liver enzymes that usually
does not require discontinuation of the drug if the patient’s
condition is closely monitored.19 The appropriate duration
of antibiotic therapy has not been established, but studies
show a mean recommended course duration of 3 to 4
months.6,13,17,33,39 In one study investigators suggested at
least 1 year of albendazole therapy after neural decompression.7
Reports also indicate that irrigating the wound with hypertonic saline or a diluted Betadine solution after cyst removal helps osmotically destroy and disrupt the parasites,
although this remains unproven.6,15,29 In a few studies,
researchers have detailed treatment alternatives for inoperable cases or patients in whom surgery is contraindicated. Lam, et al.,25 describe a case of inoperable vertebral
hydatidosis treated with albendazole and praziquantel that
resulted in a reversal of imminent paralysis. Patients have
also been reported to have been successfully treated using
CT-guided needle aspiration and hypertonic saline irrigation.41
Recurrence remains a major problem in spinal hydatidosis; the literature cites rates of 30 to 100%. Given this
Neurosurg. Focus / Volume 17 / December, 2004
Recurrent spinal hydatidosis in North America
high rate of recurrence, spinal hydatidosis has a poor
prognosis, and has been compared to spinal malignancy.18
Reported mortality rates vary, with a range from 3% to
more than 50%.1,8,24,49 In one study researchers suggest a
mean life expectancy of 5 years after onset of spinal
involvement.22 Nevertheless, with improved neuroimaging, aggressive resection, and more extensive experience
with current anthelmintic drugs, the recurrence rates may
decline.
CONCLUSIONS
We report on a patient with a recurring thoracic extradural hydatid cyst; the recurrence was presumably due to
misdiagnosis and therefore inadequate treatment. A literature review concerning presentation, diagnosis, neuroimaging, treatment, and prognosis of spinal hydatidosis is
presented. Hydatid disease of the spine is rare, especially
in the US, but should be considered in the differential
diagnosis of patients presenting with progressive myelopathy secondary to intraspinal masses and who have had
contact with areas in which hydatidosis is endemic. The
diagnosis must be clearly established, appropriate surgical
therapy instituted, and anthelmintic chemotherapy administered with vigilant follow-up review maintained to
achieve optimal and lasting results.
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Manuscript received October 15, 2004.
Accepted in final form November 4, 2004.
Address reprint requests to: Walter D. Johnson, M.D., Division
of Neurosurgery, 11234 Anderson Street, Room 2562, Loma Linda,
California 92354. email: [email protected].
Neurosurg. Focus / Volume 17 / December, 2004