Orbital myocysticercosis: Ophthalmic presentation and long term outcomes

The extraocular cysticercosis can have a myriad of clinical presentations depending on the cyst stage, its site, size, and relation to adjacent vital ophthalmic structures. Orbital myocysticercosis masquerades various ophthalmic manifestations, both clinically and radiologically. It may mimic preseptal and orbital cellulitis, idiopathic orbital inflammatory disease, optic neuritis, acquired blepharoptosis, subperiosteal abscess, double elevator palsy, or double depressor underaction, Duane's retraction syndrome, and Brown's syndrome. Hence, the initial presentations may pose a significant diagnostic dilemma to primary ophthalmologists.

The radiological features may mislead in cases having cysticercosis cyst without typical scolex. A fusiform or localized enlargement of the rectus muscle, absence of scolex, atypical location of the cyst, and severe localized inflammation are such scenarios. There is a lacuna about the atypical presentations and diagnostic criteria of orbital myocysticercosis. Manpreet Singh and team conducted a study inferring the clinical and radiological features of suspected or diagnosed subconjunctival and atypical orbital myocysticercosis.

Retrospective analysis of diagnosed subconjunctival and atypical (strabismus, diplopia, and blepharoptosis) orbital myocysticercosis was performed. A diagnostic criterion (2 of the 3) among clinical features, radiological findings, and treatment response was used in study. A minimum of "post‑treatment" follow‑up of 12 months was observed.

Any 2 of the 3 below‑mentioned criteria were considered as diagnostic of orbital myocysticercosis. The criteria included:

1. Clinical features (in various combinations): orbital pain with restricted ocular motility, diplopia, blepharoptosis, proptosis, squint, localized conjunctival inflammation, and localized yellowish subconjunctival nodule.

2. Radiological findings (CT/MRI scans): the presence of cyst with or without scolex inside the rectus muscle, enlarged rectus muscle (myositis), fusiform muscle belly enlargement, with or without neurocysticercosis.

3. Desired treatment response: complete resolution of symptoms within 6–8 weeks and/or radiological evidence of the disappearance of cyst.

Thirty‑five patients were included with a mean age of 16 years having male predominance (n = 22, 62.8%). All had a unilateral presentation, with 24 (68.6%) patients having subconjunctival cysticercosis, of which 22 were located in close proximity of the rectus muscle insertion. At presentation, 10 patients had diplopia, 7 had strabismus, and 6 had face turn. Pseudo Duane's and pseudo‑Brown's syndrome were noted in 5 and 4 patients, respectively. Radiologically, single muscle myositis without scolex was seen in 12 (34.3%) cases. All patients first received medical treatment, and surgical intervention (cyst removal) was attempted after treatment failure. Complete resolution of symptoms was noted in 22 (after medical treatment only) and in 8 (after surgery).

Cysticercosis usually affects more vascularized tissues like the brain, the muscles of the head and neck, tongue, and heart. The glucose or glycogen content of these tissues and the rate of blood flow are directly responsible for this preponderance.

Typical findings of cysticercosis cyst constitute inflammatory and mass effect features. The masquerading clinical presentations of atypical orbital myocysticercosis in the study were blepharoptosis, yellowish subconjunctival nodule with inflammation, strabismus, diplopia, face turn, and pseudo‑Duane's and pseudo‑Brown's syndrome. The incidence of cysticercosis has been found to be more common in the younger population.

In atypical clinical presentation of orbital and adnexal cysticercosis, radiological investigations like USG, CT scan, or MRI of orbits may provide the diagnostic clues (like highly reflective or hyperdense scolex). The cystic or mass‑like lesions without scolex inside an extraocular muscle with surrounding inflammation may point toward myocysticercosis.In few occasions,there might be more than one cystic or mass‑like lesion inside or arising from the recti muscles.

The management of orbital myocysticercosis is medical in >95% of cases and a few need surgical intervention for the removal of nonresponding cysts. In either of the management strategies, residual restriction of extraocular movements in extreme gaze can be seen as the sequelae of orbital myocysticercosis. However, in the case of subconjunctival cysticercosis, the surgical management can be performed earlier at a stage when acute anterior inflammation has subsided. It may reduce the overall duration of the medical treatment and provide faster and effective relief from the symptoms. The chance of extraocular muscle movement restriction after the surgical treatment is also negligible in the case of subconjunctival cysticercosis.

Clinical and radiological features of patients having subconjunctival and atypical orbital myocysticercosis

Symptoms Signs

Conjunctival congestion Restricted extraocular movements

Orbital pain Subconjunctival cyst

Diplopia Orbital sulcus fullness

Proptosis Pseudo Duane's retraction

Strabismus Pseudo Brown's syndrome

Face turn Blepharoptosis

Best corrected visual acuity <6/60=3 patients; >6/60=32 patients

Orbital imaging features

Extraocular muscle involved Atypical features

Medial rectus Single muscle myositis without scolex

SR‑LPS complex Diffuse single muscle myositis

Superior oblique Pseudo‑abscess

Lateral rectus Multiple loculations

Inferior rectus Fusiform belly enlargement

Location of cyst in muscle belly: Anterior 1/3rd ; Central 1/3rd ; Posterior 1/3rd

The authors concluded, "With our experience of atypical and subconjunctival cysticercosis, we suggest keeping the odds of having a diagnosis of cysticercosis high in the younger population, especially in an endemic region like ours. Subconjunctival cysticercosis is a part of anterior myocysticercosis, which needs to be dealt with medical treatment followed by surgical intervention (if needed). A patient having diplopia with restrictive strabismus and inflammation may need orbital imaging as a part of the investigative protocol. Overall, in suspected orbital myocysticercosis patients, a satisfactory clinical response to the medical management may be considered as a diagnostic sign."

Source: Singh M, Sharma M, Chaurasia S, Grewal AM, Kaur S, Kaur M, et al. Ophthalmic presentations and long-term outcomes of subconjunctival and atypical orbital myocysticercosis. Indian J Ophthalmol 2021;69:2782-7.