Echinococcus in the orbit: an unusual hideout

Isolated involvement of the orbit by hydatidosis is extremely rare. It is a parasitic infestation due to a tapeworm called Echinococcus Granulosus. It is an uncommon disease in head and neck region as it commonly manifests in the lungs and liver. When seen in head and neck, it has been found in the orbit, paranasal sinuses and salivary glands. Orbital hydatidosis per se forms only 1% of all types of hydatid disease. It is endemic in Africa, Middle East and Southeast Asian countries including India. In orbital hydatid disease, patients usually present with unilateral proptosis and diminution of vision. Proptosis is classically painless. Total surgical removal remains the mainstay of treatment. A 30-year-old female belonging to lower socio-economic status, presented with left eye proptosis since 2 years. There was a gradual increase in proptosis associated with diminution of vision over the last 4 months. This finally led to complete loss of vision in a period of two months. Computed tomography scan showed two soft homogenous non-enhancing cystic structures present in the orbit abutting the optic nerve without any intracranial extension; most likely differentials are a developmental cyst, hydatid cyst, epidermoid cyst, rhabdomyosarcoma or a nerve sheath tumor. Magnetic resonance imaging showed two T1 hypointense non-enhancing, T2 hyperintense soft cystic capsulated space-occupying lesions present in the extraconal compartment of orbit abutting the optic nerve, likely to be lymphangioma or a hydatid cyst. Surgery was planned and endoscopic orbital decompression was done. Sago grain-like granules were seen pouring out of the cysts. Cyst walls were completely removed in piecemeal and the specimen was sent for histopathology. Immediate intra-operative reduction of proptosis was seen. The final histopathological report was suggestive of hydatid cyst.