Unlocking Rare Cerebral Hydatid Cysts in 8-Year-Old Girl
Authors: Daghistani Ghaida 
Published: February 2025

Brief medical history: An 8 year old girl, previously healthy, presented to ER with 20 days h/o blurred vision + right eye progressively increasing in size. Intermittent headache mainly on the right side of head, but no history of fever, vomiting, neurological deficit, urinary retention or incontinence. On examination she was found to have Papilledema.

Diagnostic hypothesis: When formulating a differential diagnosis for an enlarging eye size it is important to know if the sinuses are involved, optic nerve, ocular muscle, cavernous sinus and the brain parenchyma.

Radiological findings with clinical outcome: A CT scan performed and it showed a large left frontal intra-axial cystic lesion measuring 9 x 9 cm with multiple peripheral solid nodules and mass effect on the brain parenchyma.

Differential diagnosis: The differential diagnosis of enlarging globe size and blurred vision includes Orbital cellulitis as it shows soft tissue swelling, diffuse edema and abscess formation. Optic neuritis will show optic nerve enhancement on MRI with gadolinium contrast. Orbital tumors as it will cause mass effect in the orbits displacing the optic nerve. Thyroid eye disease as it shows enlarged extra ocular muscle with no tendon involvement. Cavernous sinus thrombosis as it shows non-opacification of cavernous sinus with venous congestion. Brain tumor with mass effect are involved in the differentials.

Outcome, with definitive pathological diagnosis: Based on radiology finding the pathway was leading toward cerebral hydatid cyst with mass effect pushing the globe forward. The patient subsequently underwent surgical excision of the mass and the surgical specimen was sent to the pathology department.

Axial contrast-enhanced CT scan demonstrates a large left frontal intra-axial cystic lesion measuring 9 x 9 cm with multiple peripheral solid nodules.

Illustrative images of macroscopic and/or microscopic should be inserted, such as specimen photograph

The cyst is large around 15 to 16 cm in diameter encapsulated in a transparent plastic bag, roughly spherical, and has a milky, translucent appearance. It likely represents a cyst formed by the parasitic infection of *Echinococcus*.

The surface appears smooth and glossy, typical of the outer pericyst layer.
There are also visible pale or whitish circular spots, which represent internal brood capsules or daughter cysts.

Gross appearance of a hydatid cyst after it has been surgically opened.

The cyst membrane is visible and has a translucent, gelatinous appearance. This likely represents the *laminated layer*, which is part of the cyst's outer wall.

There are whitish nodules or masses within the cyst, which are likely protoscoleces or brood capsules. These are the larval stages of *Echinococcus*.

The opened membrane has a thin, floppy appearance.

Conclusion:

Hydatid cysts present as well- circumscribed, fluid-filled, round lesions that may cause mass effect and compression of the surrounding parenchyma particularly the brain and orbit.

Hydatid cysts are non enhancing, homogenous appearing cyst.

Early detection is crucial to prevent complication, as cyst rupture or expansion can lead to severe outcomes such as increase intracranial pressure or secondary infection.