Hydatid disease is the most widespread human cestode infection in the world. In this serious parasitic infection, humans are incidental hosts and acquire the disease as a result of fecal-oral contamination either directly by ingesting the parasite eggs through contact with dogs or indirectly through consuming contaminated water or food (
Hydatid cyst involving the spine is a rare finding. Braithwaite and Lees (
6) categorized spinal hydatid disease according to the occurrence site: type 1, primary intramedullary hydatid disease; type 2, intradural extramedullary hydatid cyst; type 3, extradural intraspinal hydatid cyst; type 4, hydatid disease of the vertebrae; and type 5, paravertebral hydatid disease. Overall, the first 3 types are uncommon. Also, intradural hydatid disease presents at younger age, compared to extradural lesions and more frequently presents as a single cyst. The present case was a multiple intradural extramedullary type, which presented at younger age. Similar cases of intradural extramedullary spinal hydatidosis have been also discussed by M. Ahmad et al., Lotfinia I et al., and Senol N. et al. ( 7- 9).
There are various diseases and pathological conditions, which closely mimic spinal echinococcosis, thereby posing difficulty in diagnosis. The most important differential diagnosis in Indian population is tuberculosis of the spine, commonly known as Pott disease. However, the cystic nature of the lesion in hydatid disease, without sclerosis in the host bones, is typical. On the other hand, destructive and necrotic nature of the lesion, associated with damage to the disc surface, is common in Pott disease. Histopathological examination can differentiate these conditions.
The chance of misdiagnosis is higher in areas where both hydatidosis and tuberculosis are endemic (
10, 11). Other conditions, such as arachnoid cyst, pyogenic infection, mycosis, and spinal abscess, require proper evaluation, as they can closely mimic spinal hydatid cyst. Arachnoid cysts occur as single or multiple cysts and are frequently extradural. However, they can be easily ruled out, given the decreased inflammatory response on histopathological examination. In the present case, abundant inflammatory responses and giant-cell reactions were reported, thereby ruling out the diagnosis of arachnoid cyst. Also, spinal abscess and mycotic infection can be confirmed through culture and sensitivity tests ( 12).
An accurate preoperative diagnosis of spinal hydatid cyst is very difficult, as there are no pathognomonic signs or conclusive tests (
13, 14). There is a wide variety of clinical symptoms favoring hydatidosis, including urticaria, pruritus, edema, asthma, dyspnea, vomiting, diarrhea, colicky abdominal pain, and even anaphylactic shock, which occur as a consequence of cystic fluid spillage ( 15, 16).
Serological tests are often negative, with sensitivity as low as 25% - 56% (
11). A negative serology should not exclude the diagnosis of hydatid disease in case of suggestive imaging results. MRI is the best imaging modality for determining the location of the cystic lesion and the exact spinal levels involved. Therefore, a clinicoradiological correlation is needed to make a presumptive preoperative diagnosis of spinal hydatid cyst. However, histopathological examination of the excised cyst can finally confirm the diagnosis.
Depressive laminectomy with total radical excision of the cyst, aiming to decompress the epidural region without preoperative rupture of the cyst, remains the best curative procedure and treatment of choice for reversing the process of cord compression (
17). However, rupture of the cyst inevitably leads to the formation of multiple cysts with recurrences no treatment procedure would overcome. Therefore, meticulous care should be taken while performing surgery in such cases to avoid spillage of the cyst content.
Anthelmintics are prescribed postoperatively to prevent any dissemination or systemic involvement (
11). Albendazole doses, recommended by the world health organization (WHO) for visceral hydatid disease, range from 10 to 15 mg/kg/day. To achieve scolicidal blood levels, treatment with albendazole should be initiated 4 hours (or > 4 hours) before surgery, considering the high to inevitable risk of cyst rupture ( 18). Follow-up is advised for any recurrence or systemic involvement of hydatid disease. Although MRI is not specific to hydatid disease, it should be the modality of choice in the follow-up of spinal hydatid cyst to ensure early detection of recurrences.
In conclusion, spinal hydatosis is a rare phenomenon, which should be always considered in the differential diagnosis, especially in areas where echinococcosis is endemic. Detailed preoperative evaluation with MRI and CT scan is necessary in localizing the lesion and planning the surgical approach. Postoperative pharmacological administration of anthelmintics, commonly albendazole, is advised due to easy absorption and better efficiency according to WHO recommendations.
Accurate and conclusive diagnosis of hydatid disease is of great importance, as it facilitates suitable surgical planning and proper intraoperative measures to prevent spillage, which can be only assumed when there is already a preoperative suspicion. Decompression of a compromised spinal cord with stabilization may lead to the reversal of symptoms, associated with reduced morbidity and disability. Therefore, hydatid cyst should be always considered before planning a surgical approach while dealing with cystic pathologies of the spine.