Inverse Duane’s retraction syndrome: rare presentation of orbital myocysticercosis

<i>Introduction</i>: Cysticercosis is a systemic parasitic disease caused by the larvae of the tapeworm Taenia and has varied clinical manifestations. Ocular involvement can be intraocular or extraocular and can mimic various etiologies and patterns of strabismus. This study reports 3 cases of orbital myocysticercosis mimicking clinical presentation of inverse Duane's retraction syndrome and discuss the clues to the clinical diagnosis. <i>Methods</i>: Retrospective review of medical records of three patients with medial rectus muscle cysticercosis with clinical findings mimicking acquired inverse Duane's retraction syndrome. <i>Results</i>: Review of medical records identified 3 patients with myocysticercosis presenting as inverse Duane's retraction syndrome with exotropia, esotropia and orthophoria in primary gaze, restricted horizontal movements and globe retraction in abduction. Ultrasound B scan or orbital computerized tomography scan confirmed the diagnosis of medial rectus muscle cysticercosis in all patients. All 3 patients were treated with oral albendazole with resolution of the cyst on follow up imaging and improvement in clinical findings. <i>Discussion</i>: Cysticercosis is a common parasitic infection in India and responds well to medical management. These 3 cases highlight the unusual presentation of medial rectus muscle cysticercosis presenting as acquired inverse Duane's retraction syndrome. Sudden onset strabismus and restricted extraocular movements along with signs of orbital or adnexal inflammation in a child or young adult residing in endemic areas should be evaluated to rule out myocysticercosis. Inflammation is usually painless with minimal tenderness despite marked signs of orbital or adnexal involvement. Diagnosis relies on high clinical suspicion and imaging such as ultrasound B scan, MRI, or CT, which can reveal the cyst and scolex within the muscle. Relative rarity of this presentation of myocysticercosis as inverse Duane's retraction syndrome makes it imperative for clinicians to be aware of this entity to clinch the diagnosis early and initiate prompt treatment.