Primary Orbital Hydatid Cyst in an Elderly Patient

Case Report

A 74-year-old previously healthy man, member of a poor farming family living in close contact with dogs, presented with a 10-month history of painless proptosis and gradual loss of vision of the left eye. On admission, ophthalmologic examination showed conjunctival chemosis and severe proptosis of the left eye (grade III), which was displaced superiorly. Ocular motility was restricted in all directions, and visual acuity of the left eye was 0/10. The left eyeball was nonreducible and nonpulsatile. Fundoscopic examination revealed a blurred optic disc of the left eye. The contralateral eye was within normal limits. General physical examination of the patient showed no abnormalities, and laboratory tests were normal. Hydatid serologic tests were negative. Ultrasonography of the left orbit demonstrated a 40 × 18 mm well-defined, unilocular, anechoic lesion. Computed tomography (CT) scan (Fig. 1) showed a well-delineated, hypodense, retrobulbar cystic mass pushing the globe anteriorly and causing erosion of the orbital floor, roof, and sphenoid bone with mass effect on the ethmoid bone. This lesion did not enhance after injection of contrast medium. On the basis of radiological findings, a hydatid cyst was suspected preoperatively. A frontoparietal craniotomy and orbitotomy were performed and the cystic mass removed totally, but the cyst wall ruptured during the resection. Histopathological examination of the surgical specimen confirmed the presence of hydatid cyst. Chest radiograph and abdominal ultrasonography showed no evidence of the hydatid disease involving any other organ system. Postoperative course was uneventful, but the patient did not show significant improvement in his visual acuity. Medical treatment with albendazole was prescribed (200 mg once daily for six weeks), but the patient was lost to followup.

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FIG. 1.

Axial computed tomography scan demonstrating a voluminous, hypodense, unilocular, retrobulbar cystic mass enlarging the orbital cavity and pushing the eyeball anteriorly with erosion of the sphenoid bone and mass effect on the ethmoid bone.

Discussion

Hydatid disease is endemic in cattle- and sheep-raising regions of the world, including Tunisia, where it constitutes a serious health problem. The orbit is among the uncommon sites of echinococcal infestation, even in hyperendemic areas. Orbital hydatid cyst is a primary echinococcosis and is generally unilateral [2]. It is uncommon to find other simultaneous hydatid cysts elsewhere in the body [2,3]. Patients with orbital hydatidosis are mostly children or young adults with a mean age of 16 years, with both sexes affected equally [4]. A preponderance of left orbital involvement over the right has been observed [1]. As a rule, the symptoms are insidious and the clinical picture progresses over a period of several months, as was the case in our patient. The cystic growth may be occasionally preceded by trauma [5]. The majority of patients with intraorbital involvement present with unilateral proptosis, and in some patients there is mechanical restriction of ocular movements and visual impairment. Other clinical features include ocular tension or pain, chemosis, lid edema, papilledema, and optic atrophy [4]. In our patient, loss of vision was probably related to optic nerve dysfunction secondary to the pressure effects caused by the large size of the cyst. Usually, orbital hydatid cysts are located in retrobulbar tissues, either within the muscle cone (up to 60%) or outside in the superolateral or superomedial angles [4,6]. According to their anatomical locations, hydatid cysts may erode the orbital walls toward different directions as observed in our patient [4,6,7]. Because of the integrity of the cyst wall in the orbit, serologic test results may be inconsistently positive in 50% of cases and an elevated eosinophil count is present in only 25% of cases [4,7]. In the present case, serologic tests were negative and there was no increase in eosinophil count. Computed tomography (CT) and magnetic resonance imaging (MRI) have now become the radiological modalities of choice in the diagnosis of orbital hydatid cyst. CT describes the cyst as a hypodense, unilocular, well-defined, thin-walled, homogenous mass with a hyperdense rim, whereas MRI shows a cystic lesion with a low-intensity signal on T1-weighted images and a high-intensity signal on T2-weighted images [4]. Color Doppler study of the orbit is a new imaging modality for making a correct diagnosis. It may give more detailed information about the changes in blood flow in the central retinal artery and vein, posterior ciliary artery, and ophthalmic artery owing to compression by the cystic mass [8,9]. The differential diagnosis includes any well-circumscribed, non-pulsatile, and non-reducible lesion such as an abscess, an (epi)dermoid cyst, a hematocele, a teratoma, an encephalocele, or a mucocele. Careful radiological evaluation coupled with the clinical findings usually allows differentiation among these lesions. The only definite treatment for orbital hydatid cyst is surgical removal. Unfortunately, delay in establishing diagnosis and management of the disease causes complete loss of vision, as was the case in our patient. Because of the restricted area inside the orbit, total extirpation of the cyst without rupture is almost impossible. This causes spillage of the contents of the cysts, leading to secondary dissemination with local recurrence. Postoperative treatment is therefore of great importance. Albendazole has been shown to be effective in such cases [1,4,7]. The diagnosis of hydatid cyst is relatively easy in patients from endemic countries, based on the clinical features, radiological investigations, and sometimes serology. Nevertheless, in some cases, a definite diagnosis must depend on histopathological examination of the surgical specimen.

Hydatid cysts should be included in the differential diagnosis of unilateral proptosis in patients from countries where hydatidosis is endemic. Early preoperative diagnosis of the disease is important to avoid cyst rupture so that severe allergic inflammatory reactions, seeding, and recurrence of the disease can be prevented.