Ocular Cysticercosis

Ocular cysticercosis may affect any portion of the visual pathway from the orbit to the visual cortex. The common sites of ocular involvement include retina/subretinal space (41%), vitreous cavity (27%), subconjunctival space (21%), anterior segment (8%) and lids/orbit (4%) (Ziaei et al. 2011). The symptoms depend on the location and problems caused by the mass effect of the cyst or inflammation due to the dying parasite. Review of symptoms may reveal a history of epilepsy (Foster and Vitale 2001; Ziaei et al. 2011).

Intraocular cysticercosis may be asymptomatic or present with diminution of vision, floaters, pain, photophobia or red eye. Symptoms may occur for a few weeks or months before presentation. Visual acuity varies from a slight blur in vision in case of peripheral subretinal cysticercosis to hand movement in case of submacular cysticercosis. Cysts may be observed in the anterior segment, vitreous, subretinal and submacular locations (Figs. 24.2, 24.3 and 24.4) (Wender et al. 2011; Sharma et al. 2003; Mahendradas et al. 2007; Kruger-Leite et al. 1985). If the cyst is alive within the eye, it often induces a mild to moderate inflammatory reaction in the anterior chamber and/or the vitreous. It may be seen as spherical, translucent cyst with a scolex that undulates with evagination or invagination in response to the examining light. A dying parasite can lead to intense inflammatory reaction due to the liberation of chemical toxins, which can even lead to blindness and phthisis (Fig. 24.5). Retinal oedema, haemorrhages, subretinal exudates, sheathing of retinal vessels, exudative retinal detachment, retinal pigment epithelial disturbances and optic disc hyperaemia may also be seen. Optic nerve involvement is a very rare presentation. It usually presents with marked diminution of vision and field loss with or without proptosis. Papilledema or papillitis with a relative afferent papillary defect are common presenting signs (Sudan et al. 2005).

Subconjunctival involvement may be asymptomatic, present as recurrent conjunctivitis not responsive to topical antibiotics or a painful or painless swelling of the conjunctiva. The most common symptoms associated with orbital cysticercosis are diplopia (due to restrictive ophthalmopathy), recurrent pain and redness. Other presentations include gradually increasing non-axial proptosis, ptosis and lid nodules. Infection of the extraocular muscles usually causes problems due to the mass effect or the inflammatory response (Figs. 24.6 and 24.7). The most common muscle to be infected is the medial rectus (42%) followed by the superior rectus (18%), lateral rectus (15%), inferior rectus (13%), superior oblique and levator palpebrae superioris (5% each) and inferior oblique (1%) (Ziaei et al. 2011).

Diagnosis

Diagnosis is usually on the basis of history including travel to endemic regions of the world, ingestion of raw or undercooked pork or known previous infections with this tapeworm. A history of relapsing subconjunctival or orbital inflammations, subcutaneous nodules or neurologic symptoms may indicate infection with this parasite (Ziaei et al. 2011). Laboratory findings include eosinophilia in 71% cases. Enzyme-linked immunosorbent assay (ELISA) for the cysticercosal antigen is available. It has sensitivities of 65–98% and specificities of 67–100% in neurocysticercosis depending on the specific test, cyst burden, location and phase of the infection. A positive test needs to be interpreted in the context of the clinical picture (Ziaei et al. 2011; Coker-Vann et al. 1981; Rosas et al. 1986).

Imaging is the most useful test because of the highly specific appearance of the encysted parasites. The ‘Hanging drop’ sign of a sonolucent cyst with well-defined margins in orbital cysticercosis and a central circular cyst with a highly reflective scolex within the cyst in intraocular cysticercosis on ultrasonography (B scan) are highly suggestive of cysticercosis. Imaging can also be used for follow-up examinations to note the regression of the cyst following medical treatment (Ziaei et al. 2011; Honavar and Sekhar 1998; Murthy et al. 1990).

On CT scans, the cyst appears isodense to the vitreous humour while on MRI, it appears isointense to CSF on T1- and T2-weighted images. A live cyst does not enhance with contrast while the dying cyst enhances in contrast due to the surrounding inflammatory reaction. CT scan cranium shows multiple ring lesions in neurocysticercosis.

Ultrasonography of the eye reveals a cyst-like structure with a high-amplitude echo corresponding to the inner wall of the cyst and the overlying retina. A dot-like echo corresponding to the scolex may be seen in the cyst (Fig. 24.8).

Only gold members can continue reading. Log In or Register to continue

Share this:

• Click to share on Twitter (Opens in new window)
• Click to share on Facebook (Opens in new window)

Related

Related posts:

1. Ophthalmia
2. Inner Choroidopathy
3. Infection
4. Scleritis

Stay updated, free articles. Join our Telegram channel

Join