Spectral domain optical coherence tomography features of subretinal cysticercus cyst.

A 31-year-old man of Asian descent presented with loss of vision in his right eye from 6 months earlier. Best corrected visual acuity (BCVA) was limited to light perception in the right eye and was 6/6, N6 in the left one. Slit lamp examination revealed normal anterior segments bilaterally. Intraocular pressure was 8 and 14 mmHg in the right and left eyes, respectively. Fundus examination in the right eye showed a large subretinal cysticercus cyst, accompanied by total retinal detachment (RD), severe extensive subretinal fibrosis and membranes (Fig. 1A). B-scan ultrasound (Alcon Ultrascan, Alcon Laboratories, Fort Worth, Texas, USA) images illustrated total RD with a hyperechoic area within the cystic cavity suggestive of cysticercus scolex (Fig. 1B). Spectral domain optical coherence tomography (OCT) (Topcon 3D OCT-2000, Topcon Medical Systems, Oakland, New Jersey, USA) demonstrated a highly reflective cyst wall and a more hyper-reflective dome-shaped structure within the wall suggestive of the scolex (Fig. 1C). The posterior extent of the cyst could not be visualized due to its large size. T1-weighted contrast-enhanced magnetic resonance imaging (MRI) of the brain demonstrated a ring-shaped enhancing lesion in the left cerebellar hemisphere with perilesional brain edema suggestive of neurocysticercosis (Fig. 1D). The patient was referred to a neurophysician and received a three month course of oral albendazole and steroids. Eventually, he was recommended for follow-up care.

DISCUSSION

Ocular cysticercosis is caused by the growth of the larval form of Taenia solium within ocular tissues.1,2 The cysts may be located in descending order of frequency in the subretinal space (35%), vitreous (22%), conjunctiva (22%), anterior segment (5%) and orbit (1%).3

Intraocular cysticercosis usually presents with reduced vision and ocular inflammation. It is believed that the larva reaches the subretinal space through the posterior ciliary arteries.3-6 As the cyst develops, it may cause exudative retinal detachment.6

As long as the cyst remains viable, it evokes little or no inflammatory response. Once the cyst starts degenerating, an antigen, which may be a metabolic by-product or toxin, leaks from the cyst and induces an inflammatory reaction, manifesting as vitritis, uveitis and sometimes endophthalmitis.3-6

Most often, the characteristic intraocular cyst can be visualized by indirect ophthalmoscopy or detected by B-scan ultrasound in the presence of hazy media.3

B-scan ultrasonography will show a curvilinear echo corresponding to the cyst wall together with an eccentric hyperechoic dot suggestive of the scolex. A-scan analysis reveals two high amplitude echoes representing the anterior and posterior walls of the cyst.

Mahendradas et al7 highlighted the features of intraocular cysticercus cyst employing spectral domain OCT; they clearly delineated the hyper-reflective wall of the subretinal cyst with a more hyper-reflective portion within its wall suggestive of the scolex/larva.

CNS involvement can be observed in approximately 90% of patients with ocular cysticercosis and MRI is superior to computed tomography (CT) in detecting lesions of neurocysticercosis (NCC).8 In addition, MRI better illustrates cystic lesions in the base of the brain, cerebrospinal fluid (CSF) spaces as in ventricular NCC and cisternal NCC, and also with intramedullary lesions.9 The scolex may be more readily apparent on MRI than on CT. On MRI, contents of live cysts (vesicular stage) are isointense relative to CSF on T1- and T2-weighted images.10

Treatment of ocular cysticercosis is mandatory since it has been reported that 80% of untreated cases result in severe ocular damage.3 Antihelminthic drugs such as praziquantel or albendazole are effective in central nervous system and skin cysticercosis. However, antihelminthics are ineffective in ocular cysticercosis. Corticosteroids may be used in conjunction with these drugs to reduce the inflammatory response. Surgical removal of the cyst can also be performed through transretinal or trans-scleral routes.11 Systemic corticosteroid coverage is required before and after surgical removal of the cysticercus.3