We report a very rare case of a hydatid cyst in the infratemporal fossa, causing visual loss over a 10-day period, which disappeared with rapid surgical and medical treatment.

A 14-year-old girl presented with right exophthalmos and visual loss. Over a 10-day period, her visual acuity had decreased to detection of hand motion only, due to pressure on the optic nerve caused by a parapharyngeal cyst pressing through a inferior orbital fissure on the right side. A craniotomy had previously been performed for a right frontoparietal hydatid cyst. The patient had been treated intermittently with albendazole. The patient was primarily diagnosed with hydatid cyst, on the basis of her previous medical history and radiological findings, and underwent surgery. Three cysts were carefully removed from the right maxillary sinus, via a standard Caldwell–Luc approach, and the surgical area was irrigated with hypertonic saline.

Infratemporal hydatidosis is very rarely reported in the world literature, although hydatid cysts are endemic in many countries, including Iran. We discuss the common presenting features, investigation and treatment options for infratemporal hydatosis. Constant evaluation of adjacent organs is necessary, with treatment as required, due to the propensity of hydatidosis to recur in essential organs. Immediate surgery is recommended, both to prevent the development of disease and to improve the prognosis.