Key-words:
Decompression - dorsal spine - hydatid cyst
Introduction
Hydatid cyst disease is a parasitic infection caused by the ingestion of larvae of
Echinococcus granulosus cestode.[[1]] The cestode's life cycle involves two hosts–
The definitive hosts: Dogs andThe intermediate or accidental host: Human beings.
Human beings become infected after the accidental ingestion of eggs of the cestode,
which are often found in the dog's fecal matter. The Larvae of the cestodes hatch
from the eggs in the human intestine. These larvae then erode the capillaries in the
intestine and migrate throughout the human body. The hydatid cysts are most commonly
found in the liver (60%–70%), followed by the lungs (10%–15%).[[2]],[[3]] Rarely it affects bone in around 0.5%–2% of cases and mainly involves the spine
in about 0.5%–1% of cases.[[4]] Out of all cases with involvement of the spine, thoracic spine involvement is most
common (50%) followed by the lumbar spine (20%), sacral spine (20%), and cervical
spine (10%).[[5]],[[6]] It can manifest local bone destruction, collapse, and instability leading to radiculopathy,
paraplegia, and quadriplegia.[[7]],[[8]] The diagnosis is usually late because of a painless asymptomatic lesion in the
initial stage of disease.[[9]] Here, we are presenting a case of hydatid cyst in the dorsal spine managed with
decompression at a tertiary health care institute.
Case Report
A 35-year-old male presented in the outpatient department (OPD) with a chief complaint
of mid-back pain for 4 years and intermittent history of fever. He also complained
of intermittent fluid discharge from a scar in the upper back. He had undergone a
surgery in his upper back 4 years ago. The details of the previous surgery were not
available with the patient. He was on presumptive anti-tubercular treatment therapy
for the past 6 months before vising us, taking into consideration of the endemic region
as prescribed by the previous physician. On examination, tenderness was elicited in
the upper dorsal vertebra, and kyphotic deformity was found. There was no deficit.
X-ray was found to be nearly normal except kyphosis in the region of D2–D6 and partial
collapse of D4. On magnetic resonance imaging (MRI), hydatid cyst disease was confirmed
to involve the D4 vertebra involving the paravertebral area [[Figure 1]]. Operative intervention was planned, and surgery was performed through the posterior
approach. D4 spinous process and part of lamina were found deficient due to previous
surgical intervention. Intact cysts in the paravertebral area were excised [[Figure 2]]. Intraoperatively, the vertebral column integrity was found to be intact after
the total excision of all the cysts and surrounding soft tissues without any loss
of stability. The wound was closed in layers after giving thorough wash. The excised
hydatid cysts were sent for histopathological examination and that further confirmed
the diagnosis [[Figure 3]]. The patient was subjected to perioperative and postoperative Albendazole treatment
for 6 months. He was mobilized postoperative day-1 with Taylor's brace, and the brace
was continued up to 6 weeks. He was followed up on an OPD basis at 2 weeks, 6 weeks,
3 months, 6 months, and 1 year. There was no recurrence till his last visit.
Figure 1: (a) Magnetic resonance imaging of the dorsal vertebra in the sagittal plane, T2 sequence
showing hydatid cysts in the D4 region with partial collapse of D4 vertebra. (b) Magnetic
resonance imaging of the dorsal vertebra in the sagittal plane, myelo sequence showing
hydatid cysts in the D4 region. (c) Magnetic resonance imaging of the dorsal vertebra
in an axial plane withT2 sequence showing hydatid cysts in the D4 region. (d) Magnetic
resonance imaging of the dorsal vertebra in an axial plane, T1 sequence showing hydatid
cysts in the D4 region
Figure 2: Intraoperative picture showing excised intact hydatid cysts
Figure 3: Histopathological examination. A - Scolex of the hydatid cyst. B - Cyst wall of the
hydatid cyst. C - Germinative layer of the hydatid cyst
Discussion
Patients of spinal hydatidosis usually are asymptomatic and generally present with
insidious onset of pain in the affected region. Few become symptomatic either due
to cord compression or due to the collapse of the vertebral body, which usually happens
after a prolonged infective period, causing a delay in diagnosis. However, half of
the patients with spinal hydatid cyst disease may have neurological involvement at
the time of presentation.[[10]]
Radiological investigations in the form of plain radiographs and computed tomography
(CT) scans can delineate bony destruction.[[11]],[[12]] MRI, however, is the investigation of choice.[[13]],[[14]] MRI provides detailed information on the extent of the lesion and the amount of
cord compromise. The cysts are hypointense on T1-weighted images and hyperintense
on T2-weighted sequences. The hydatid cyst usually contains a single thin wall, and
the cystic fluid has the same intensity as cerebrospinal fluid on MRI images. The
cyst walls or content do not show enhancement with gadolinium contrast. Biopsy or
aspiration of the cyst has a significant risk of diffusion and precipitating anaphylactic
reaction. Hence, these invasive investigations should not be done to establish the
diagnosis.[[15]]
Surgical resection of the cystic lesions en-bloc remains the treatment of choice.
The histopathological examination establishes the diagnosis, as the lesion may mimic
various other pathologies. The differential diagnosis can be a solitary bone cyst,
aneurysmal bone cyst, arachnoid cyst, giant cell tumor, chondrosarcoma, neurofibromatosis,
and tubercular spondylodiscitis. Misdiagnosis based on clinicoradiological findings
is common[[16]] and may have disastrous consequences because of intraoperative rupture of the cyst
wall. In our case, the patient was suspected of having tubercular spondylodiscitis
and had been on anti-tubercular drugs for a prolonged period. Definitive diagnosis
was made during surgery when the characteristic grape-like cysts were noted during
surgery.
A posterior approach with laminectomy provides access to the intraspinal lesion.[[5]] Anterior transthoracic approaches may be required if the cysts are predominantly
in the prevertebral or paravertebral location. In our case, laminectomy was done to
remove the intraspinal cysts. The paravertebral cysts were removed after costotransversectomy.
No instrumentation was done. A review of literature done after surgery, however, revealed
that reconstruction with transpedicular screws, metallic cages, or bone graft is usually
recommended for maintaining spinal stability.
Dew/Braithwaite and Lees[[4]] described a classification of spinal hydatid cystic lesions depending on its location
as (1) Primary intramedullary hydatid cyst, (2) Intradural extramedullary hydatid
cyst, (3) Extradural intraspinal hydatid cyst, (4) Intraosseous/vertebral hydatid
cyst, and (5) Paravertebral hydatid cyst disease. This classification helps in planning
the surgical approach for excision of the cysts. It also helps as a prognostic indicator
for recurrence after surgery. Turgut et al., in a series of 72 spinal cystic echinococcus
lesions, found that intradural lesions had the least recurrence rate (RR) after surgery
(0% in their series). They believed that this favorable outcome was because of solitary
intradural cysts. Vertebral (RR 32%) and paraspinal (RR 33%) lesions were associated
with far higher rates of recurrence than intraspinal extradural (RR 6%) location.
The two main factors determining the RRs after surgery are– complete resection and
unruptured resection of the daughter cysts. The intraoperative rupture of cyst causes
an increase in a relapse rate exceeding 40%.[[17]] Hence, spillage of the cyst contents and associated recurrence is often high.
Since the rupture of cysts and spillage of contents are almost inevitable during surgical
resection, various scolicidal agents are routinely used to sterilize the surgical
field and prevent contamination. These scolicidal agents are, however, not active
against intact daughter cysts and are only effective against spilled protoscolices
from the ruptured cysts. The intact daughter cysts require adjuvant chemotherapy with
various benzimidazole derivatives (albendazole or mebendazole). The scolicidal agents
in vogue are– povidone-iodine, hypertonic saline, hydrogen peroxide, formalin, silver
nitrate, cetrimide, and ethacridine lactate. Twenty percent hypertonic saline appears
to be the most popular and effective agent among these options. The reason behind
the popularity of hypertonic saline is its safety profile and easy availability.
Medical management with various benzimidazole derivatives like albendazole has been
in vogue based on their efficacy in visceral hydatid lesions. However, their effectiveness
in preventing recurrence in osseous lesions is debatable. Recently, few authors have
reported satisfactory results with their use in extensive or inoperable hydatid disease.
El Mufti et al., in their series of inoperable spinal hydatid disease, reported a
cure rate of 53% with albendazole treatment at 2 years follow-up. In the absence of
sufficient data regarding the use of albendazole in spinal lesions, most surgeons
follow a dosage regimen based on the WHO recommendations for visceral hydatidosis
(15 mg/kg/day). Few authors advocate the initiation of albendazole therapy 4 h before
surgery to ensure adequate blood levels during the perioperative period. Although
there is no evidence-based study on the optimal duration of albendazole therapy, most
authors use it for 6 months, with few advocating its use for longer. Indefinite use
of these benzimidazoles has also been reported in few cases with extensive or recurrent
hydatid lesions.
Treatment in the form of CT-guided Puncture of the cyst, aspiration of the cyst fluid,
injection of a scolicidal agent, and re-aspiration of the cyst content approach[[18]] and radiotherapy[[19]],[[20]] are also reported in the literature with variable success rate. Despite anthelmintic
therapy and aggressive surgical treatment, it has recurrence ranging from 30% to 100%.[[21]]
Conclusion
Hydatid cyst disease in the spine is a rare disease but associated with high morbidity
despite significant advances in diagnostic imaging techniques and surgical treatment.
It should be considered a differential diagnosis in the case of spinal canal compression.
For a provisional diagnosis, the MRI is the investigation of choice. Surgical decompression
is the main stray of treatment along with antihelminthic therapy. This disease has
high RRs, especially in cases with vertebral bone involvement. Hence, a close follow-up
is required after initial treatment.
Clinical message
The hydatid cyst disease in the spine is a rare pathology and diagnosis can be challenging.
This disease may mimic tuberculosis, which is one of the most typical diseases in
the endemic region. Confirmation should be made with MRI in such cases to avoid misdiagnosis.
