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Ophthalmic presentations and long-term outcomes of subconjunctival and atypical orbital myocysticercosis

Purpose: To study the clinical presentation, radiological features, diagnosis, and treatment response in subconjunctival and atypical orbital myocysticercosis. Methods: 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 our study. A minimum of “post-treatment” follow-up of 12 months was observed. Results: 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). Conclusion: In the majority, the subconjunctival cysticercosis is found in proximity to the rectus muscle insertion, as a part of orbital myocysticercosis. In atypical scenarios, a satisfactory response to medical treatment can be considered as diagnostic of cysticercosis.

The radiological features may mislead in cases having cysticercosis cyst without typical scolex. [7,15,16] A fusiform or localized enlargement of the rectus muscle, absence of scolex, atypical location of the cyst, and severe localized inflammation are such scenarios. [8,9,15] There is a lacuna about the atypical presentations and diagnostic criteria of orbital myocysticercosis. Moreover, subconjunctival or conjunctival cysticercosis has been mentioned as unusual cases in research articles and case reports. [17][18][19][20][21] Hence, we conducted a study inferring the clinical and radiological features of suspected or diagnosed subconjunctival and atypical orbital myocysticercosis. Informed consent was obtained from all patients for the publication of their nonidentifiable clinical images in scientific journals. Our study adhered to the tenets laid by the Declaration of Helsinki.

Methods
Ours is a retrospective study of patients having subconjunctival and orbital myocysticercosis who presented to our institute Singh, et al.: Conjunctival and atypical orbital myocysticercosis from January 2014 to December 2018. The ethical clearance to conduct this study was duly obtained from department on 30.11.2019. The clinic record files and telephonic conversations with patients for additional information were used to fill the study sheet. All patients were clinically suspected to be subconjunctival [ Fig. 1a-d] or orbital myocysticercosis and orbital imaging was requested for its detection, confirmation, and/or monitoring of the disease.
T h e d a t a i n c l u d e d p a t i e n t d e m o g r a p h i c s (age, gender, laterality, and duration of presentation), clinical features (symptoms and signs), working diagnosis, imaging, treatment advised (medical only/medical + surgical), and clinical outcomes. The ophthalmic examination records included visual acuity, extraocular movements, eyelid and adnexal details, exophthalmometry (if required), and detailed ocular examination on slit-lamp biomicroscopy and indirect ophthalmoscopy. The detailed fundus examination of all patients ruled out intraocular cysticercosis before starting antihelminthic treatment to prevent vision decline. The patients having intraocular cysticercosis were excluded from our study.
The radiological features of ultrasonography (USG)/computed tomography (CT)/magnetic resonance imaging (MRI) were observed for extraocular muscle involved, location of cyst in the muscle (anterior half/posterior half), and presence of coexisting neurocysticercosis (cranial imaging) [ Fig. 2a-d]. The clinical and radiological images were retrieved from the image data bank of our clinic.
In the primary management, oral albendazole (15 mg/kg/day) with oral steroids (1 mg/kg, same day) was prescribed to all patients for 4-12 weeks depending upon the speed of response. Topical fluorometholone, 0.1% suspension, was used in all to reduce the ocular surface inflammation [Figs. 1b, 3b and 4a]. A few cases required surgical excision for subconjunctival and anterior myocysticercosis cysts. Histopathology was duly performed for the excised tissues and cysts. Medical treatment failure was described as minimal or no resolution of symptoms after 6 weeks of continuous treatment. The total duration of therapy, indications for surgical intervention, and the time taken for complete clinical and/or radiological resolution were noted. The patients having a minimum follow-up of 12 months after completion of the treatment were included in our study.

Results
Of 39 diagnosed patients, complete records were available for 35 patients having orbital myocysticercosis. The majority of patients were males (n = 22, 62.8%) with a median age at presentation of 16 years (range, 1-50 years). All had unilateral orbital involvement with a slight right orbital preponderance (n = 19, 54.3%). The rest of the demographic details, clinical symptoms, and signs are compiled in Table 1. The diagnosis at referral were conjunctivitis (n = 14), strabismus (n = 9), preseptal cellulitis (n = 8), and conjunctival retention cyst (n = 4).
Sixteen (45.7%) patients underwent orbital ultrasonography in the clinic, while all (n = 35) underwent orbital and cranial imaging. The latter was requested for detecting any neurocysticercosis lesion (active or inactive). The details of orbital imaging are mentioned in Table 1. Radiologically, the size of the cyst ranged from 4 mm to 18 mm in the longest dimension.
On presentation, 24 (68.6%) patients had reddish-yellow subconjunctival nodule representing the anterior part or complete lesion [ Fig. 1a-d]. Of these, 22 (91.7%) nodular lesions were located near the insertion of a rectus muscle. Coexisting neurocysticercosis was seen in 2 (5.71%) patients. One patient had an isolated subconjunctival nodulo-cystic lesion at the limbus without muscle involvement [ Fig. 1a]. None of our patients had disseminated cysticercosis. The diagnosis of cysticercosis was based on clinical features (n = 26, 74.3%), radiological findings (n = 18, 51.4%), and treatment response (n = 9, 25.7%). The combination of 2 of the 3 criteria was considered as diagnostic of conjunctival or atypical orbital myocysticercosis.
All 35 patients were primarily managed with medical treatment (albendazole + oral steroids), and of those, 22 resolved completely without any sequelae [ Fig. 3]. Five (14.2%) had residual extraocular muscle movement restriction in extreme gaze without clinically disturbing diplopia. Four (11.4%) patients having subconjunctival cysts showed spontaneous  Table 2.
Total 13 patients required surgical intervention, of which 5 had anterior subconjunctival lesions. Histopathology established the diagnosis of cysticercosis in 7 cases (53.8%), while in the rest, it was reported as an inflammatory cyst. Postoperatively, the majority (n = 8) showed satisfactory clinical outcomes, while five showed partial recovery with a residual deficit in extraocular motility. However, the residual diplopia was noted in extreme gazes and did not affect daily life activities. Of these, 2 patients showed clinical recurrence, which got resolved after a second course of albendazole and steroids of 4 weeks. After the medical resolution of the cysticercosis cyst, one patient had a residual scleral thinning at the same site, near the medial rectus insertion [Fig. 4]. One patient had a near-total resolution of the subconjunctival cyst and had a minimal yellowish inactive portion of the cyst, which remain the same at 12 months post-treatment follow-up [ Fig. 5a and b].  At a mean follow-up of 14.5 months, 30 patients showed complete clinical response without residual sequelae in terms of visual acuity, proptosis, and extraocular movements. Two patients showed partial clinical recovery (residual strabismus) and 3 showed no response to the medical + surgical treatment.

Discussion
Cysticercosis usually affects more vascularized tissues like the brain, the muscles of the head and neck, tongue, and heart. [22] The glucose or glycogen content of these tissues and the rate of blood flow are directly responsible for this preponderance. Orbital cysticercosis can have variable presentations, which may become a diagnostic challenge for primary ophthalmologists. Moreover, the anterior cysts present inside the rectus muscle bellies or near their insertion points have inconsistent presentations depending upon the acute or chronic stage. Hence, our study aimed to describe these atypical clinical and radiological features of orbital myocysticercosis.
As described in previous reports, the diagnosis of cysticercosis at referral is noted in around 7% of cases. [1] In orbital and adnexal cysticercosis, extraocular myocysticercosis has been reported as the most common variety. [2] Typical findings of cysticercosis cyst constitute inflammatory and mass effect features. [2,23] The masquerading clinical presentations of atypical orbital myocysticercosis in our study were blepharoptosis, yellowish subconjunctival nodule with inflammation, strabismus, diplopia, face turn, and pseudo-Duane's and pseudo-Brown's syndrome [ Table 1]. The incidence of cysticercosis has been found to be more common in the younger population and our results (mean age: 16 years) also supported the same. [1,2,22,16] 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. Honavar and Sekhar [16] have reported that around 50% of the cysts may show scolex on USG. Hence, fusiform enlargement of rectus muscle alone has been considered to be likely of cysticercosis by Sekhar and Lemke. [24] In our study, the scolex was not seen in 20 cases on orbital imaging. We experienced features like single muscle myositis (localized n = 12, and diffuse n = 6) and fusiform enlargement of muscle belly in 2 patients.
Escobar has described the pathology of neurocysticercosis as the vesicular stage, colloid phase of vesicular form, granular nodular stage, and nodular calcified stage. [25] Honavar and Sekhar [16] have described the stages of the cyst as viable, degenerative, and inactive on the basis of ultrasonography. However, the intracystic hyperreflective foci can be viable scolex or calcified inactive cysts. [16,22] These radiological masquerades should be backed by the clinical presentation and a response to the medical treatment for establishing a diagnosis of ophthalmic cysticercosis.
The differential for an ill-defined, multi-loculated, cystic lesion with thick peripheral enhancement with or without surrounding inflammatory change is a tuberculoma. Both tuberculosis and cysticercosis are endemic in India as well as other developing nations. [1][2][3][4][5][6][7][8]22,23] Classically, total and differential leukocyte counts, Mantoux test, chest X-ray, and sputum examination for acid-fast bacilli help in establishing the diagnosis of tuberculosis and help in starting appropriate treatment. For cysticercosis, blood investigations like peripheral eosinophilia, ELISA for anticysticercal antibodies, and stool examination for cysts can be helpful but are inconclusive, if negative.
Various authors have recommended considering the overall clinical presentation with available radiological features for making a diagnosis of orbital myocysticercosis and starting the treatment. [2,16,22] We have suggested the use of treatment response as the additional diagnostic criteria in perplexing situations where the clinical and radiological evidence is not sufficient for establishing the diagnosis of orbital myocysticercosis.
Subconjunctival cysticercosis is an interesting clinical entity due to its masquerading clinical features like acute conjunctivitis in the early inflammatory phase. [17][18][19][20][21] We have hypothesized subconjunctival cysticercosis to be a part of anterior myocysticercosis and have documented few cases. All had a close association between the rectus muscles of the complimentary orbital quadrant. In our study, 4 (11.4%) patients had spontaneous extrusion of the subconjunctival cysticercosis cyst. However, the role of medical treatment in spontaneous extrusion is not established, with anecdotal pieces of evidence in its favor.
The extraocular muscle myocysticercosis may masquerade any acquired motility disorder like paralytic or restrictive pathology and have presentations similar to double elevator palsy, Brown's syndrome, Duane's retraction syndrome, and sometimes total ophthalmoplegia. [11][12][13][14]22] However, a detailed strabismus evaluation with the clinico-radiological evidence of inflammatory pathology may provide clarity to the situation. The superior oblique muscle has been shown to have twin cysticercosis lesions, often probably due to its long course and closer proximity to the neuro-vascular bundle present at the orbital apex. [21] The management of orbital myocysticercosis is medical in >95% of cases and a few need surgical intervention for the removal of nonresponding cysts. [1][2][3][4][5][6][7][8]22,23] 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. Rath et al. [1] reported residual deficits in 21% of their patients at the final follow-up, while in our series, we experienced a residual deficit in 14.2% cases. Rath et al. believed that early diagnosis and treatment might limit the fibrosis and restriction of ocular movements. [1] Salim et al. [26] showed 9.83% cases to have orbital cysticercosis without the involvement of an extraocular muscle. They showed complete radiological resolution in 45% and partial resolution in 47.5% of cases. The equal importance of clinical, radiological, microbiological, and histopathological evidence has been suggested by Hamal et al. [27] for the diagnosis of cysticercosis. In treatment, the steroids have been shown to increase the plasma levels of albendazole, hence, supplementing the therapeutic response of the antihelminthic drug leading to an overall improvement in the outcomes. [28] Conclusion 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.