Hydatid disease of the spine: A rare case.

Hydatid disease or hydatidosis is the most widespread zoonosis caused by Echinococcus granulosus. Liver and lungs are the most common sites. Bone involvement is rare and reported in 0.5%-4% with spinal involvement reported in 50% of these cases. We present a case of spinal hydatidosis in a 35-year-old male presenting with lower extremity weakness and numbness. Magnetic resonance imaging (MRI) of the spine showed multiple cystic lesions at the T9-T11 level with involvement of the paraspinal muscles. The lesion was seen intraspinal, intradural, intramedullary, and epidural. Radiological impression was aneurysmal bone cyst. The patient underwent laminectomy, and the excised cysts showed characteristic features of hydatid cyst (HC) on histopathology. The patient was started on antihelminthic therapy postoperatively. MRI is a diagnostic modality for HC, but the unusual location and absence of characteristic features can cause diagnostic difficulty. A high index of suspicion should be kept in patients residing in endemic areas and presenting with unusual cystic lesion of spine.

INTRODUCTION

Hydatid disease or hydatidosis is the most widespread zoonosis caused by Echinococcus granulosus.[1] The most common sites are liver and lungs.[2] Bone involvement is rare and reported in 0.5%–4% of the cases.[3] Rare sites of location with unusual findings can make the diagnosis difficult, clinically and on radiology. We report a case of spinal hydatidosis in a 35-year-old male with a radiological diagnosis of aneurysmal bone cyst.

CASE REPORT

A 35-year-old male complained of weakness and numbness of the left lower limb for 20 days. There was no history of trauma, fever, vomiting, altered sensorium, or loss of consciousness. No bowel or bladder complaint was present. There was no history of tuberculosis present. On examination, the patient was afebrile, conscious, and alert. There was no cranial nerve deficit. Neurological examination revealed increased tone in both lower limbs. Power in the right-sided lower limb was of grade +4/5 and left-sided lower limb was 4/5 proximally and 3/5 distally. Sensation was decreased by 20% in the left lower extremity. There were no cerebellar and meningeal signs. All the hematological investigations were normal. Magnetic resonance imaging (MRI) of the spine showed a well-defined expansile heterogeneous lesion approximately of size 9.3 cm × 3.8 cm × 4.6 cm, involving T9–T11 vertebrae and posterior end of the left 6th rib [Figure 1a and b]. The lesion showed intraspinal, intradural, intramedullary, and epidural involvement. It had well-defined hypointense rim with multiple small cystic areas and was also seen extending posteroinferiorly into the posterior paraspinal muscles. Radiological impression was aneurysmal bone cyst. The patient underwent a dorsal spine laminectomy and the excised lesion was sent for pathology examination. Microscopy showed typical laminated layered structure of hydatid cyst which was infiltrating the intertrabecular spaces [Figure 1c and d]. There were a few fragments of pericyst with exuberant inflammatory response. Postoperatively, the patient was treated with albendazole and kept on regular follow-up.

Figure 1

(a) Sagittal magnetic resonance imaging images demonstrating destruction of T10 vertebral body with extension across the intervertebral disc to T9 vertebral body. (b) Axial magnetic resonance imaging scans showing multiple hyperintense cysts. (c) Characteristic laminated membrane of hydatid cyst (H and E, ×400). (d) Cyst infiltrating the intertrabecular spaces (H and E, ×400)

DISCUSSION

Hydatid disease is a zoonosis, caused by the larval stage of the cestode, E. granulosus, and is highly prevalent in countries with temperate climates.[1] The lifecycle involves definitive and intermediate hosts while humans are the accidental host.[1] Liver and lungs are involved in 90% of the cases.[2] Bone involvement is rare and reported in 0.5%–4% with spinal involvement in 50% of the cases.[3] The thoracic and lumbar spine are involved in majority of them.[2] The cyst is usually located epidurally and rarely intradurally and extramedullary.[3] It is usually confined to a single vertebral body, owing to the relative resistance to the invasion of intervertebral space.[4] The patients can have a wide spectrum of signs and symptoms ranging from simple low backache to paraplegia.[5] They can present either with compressive myelopathy or radiculopathy.[6] MRI is the preferred diagnostic modality when there is a suspicion of hydatid disease.[7] The diagnostic feature is the presence of a markedly hypointense cyst wall on T1- and T2-weighted images.[6] However, rare location with unusual finding of involvement of intervertebral disc and absence of characteristic features make the diagnosis difficult as seen in the described case. The differentials on radiology include tuberculosis, aneurysmal bone cyst, synovial cyst, traumatic pseudomeningocele, arachnoid cyst, and hemangiomas.[4] The diagnosis is confirmed at surgery by demonstration of the characteristic laminated cyst membrane on histopathology. Although the surgical removal is the treatment of choice, it should be performed without the perforation of cyst wall to avoid dissemination and anaphylactic reaction.[8] In addition, antihelminthic therapy and prolonged regular follow-up with MRI in postoperative period are mandatory to prevent the recurrence.[6] Literature describes the recurrence rate of 30%–40% and a mortality of 45%–50% on an average of 5 years after the onset of symptoms.[39] Thus, early and correct diagnosis will improve the management and survival of patients. Spinal hydatidosis should be considered as a diagnostic possibility in patients residing in endemic areas and presenting with unusual cystic lesion of spine.

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Conflicts of interest

There are no conflicts of interest.