Fundus photograph showing a cysticercus cyst in the vitreous
Fundus photograph showing subretinal cyst
Fundus photograph showing mushrooming of the cyst from the subretinal layer into the vitreous
Fundus photograph showing severe inflammation in a dead cyst
External photograph and CT scan orbits showing ptosis and restriction of elevation in the right eye before medical treatment (a) and improvement after medical treatment (b). Arrow showing the location of cyst
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 nonaxial proptosis, ptosis and lid nodules. Infection of the extraocular muscles usually causes problems due to the mass effect or the inflammatory response. 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 palpebral superioris (5 % each) and inferior oblique (1 %) .
17.5 Systemic Cysticercosis
The most common systemic manifestation is neurocysticercosis (Fig. 17.6). It is the cause of epilepsy in 50 % of partial seizures in adults. The patients may present with seizures, recurrent headaches, increased intracranial pressure or as a psychiatric disorder. Signs of meningoencephalitis may occur in case of multiple cysts. Subcutaneous nodules and inflammatory cells in the muscles may be seen [1, 2, 6].
CT scan of the brain showing multiple ring lesions in neurocysticercosis
The 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 inflammations, subcutaneous nodules or neurologic symptoms may indicate infection with this parasite . 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 [7, 13, 14].
Imaging is the most useful test because of the highly specific appearance of the encysted parasites. The characteristic “hanging drop” sign of a sonolucent cyst with well-defined margins in orbital cysticercosis is characteristic. A central circular and highly reflective scolex within the cyst is highly supportive of the diagnosis of cysticercosis. It can also be used for follow-up examinations to note the regression following medical treatment [7, 15, 16].
On CT scans, it 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 (Figs. 17.7 and 17.8).
Ultrasonography of the eye showing a globular cyst with high reflectivity inner wall and a high reflective echo corresponding to the scolex in the centre