Purpose: To describe a unique case of orbital hydatid cyst that was located solely within the medial rectus muscle.
Design: Retrospective, interventional case report.
Methods: A 20-year-old woman presented with right periocular pain induced by ocular movements. Magnetic resonance imaging studies showed a focal, well-circumscribed intramuscular cystic lesion of the right medial rectus muscle. The cyst was completely extirpated from the muscle, but some of the fluid content escaped into the surrounding tissues. Irrigation with hypertonic saline was performed.
Results: Histopathologic examination showed an acellular cyst wall with inner germinal layer, diagnostic for hydatid cyst. Two cycles of oral albendazole were administered with no recurrence.
Conclusions: In the orbit, hydatid cyst may be localized primarily within an extraocular muscle and produce painful eye movements. Hydatid cyst must be considered in the differential diagnosis of solitary cystic enlargements of extraocular muscles.