Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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October 24, 2019
Intraventricular Neurocysticercosis
- Background:
- Cysticercosis is the most common parasitic infection in the world, caused by the larval stage of the pork tapeworm Taenia solium, by ingesting its eggs from contaminated water or uncooked food or via fecal–oral contact.
- CNS lesions eventually develop in 60–90% of patients, most frequently in the intracranial subarachnoid spaces, followed by the brain parenchyma and ventricular system (usually as a fourth ventricle single lesion).
- Clinical Presentation:
- Isolated fourth ventricle neurocysticercosis can cause mechanical obstruction of CSF flow, resulting in hydrocephalus, or mass effect-induced focal neurologic deficits. In the setting of acute obstructive hydrocephalus, rapid clinical deterioration and sudden death can occur.
- Other mechanisms causing symptoms are ependymal inflammation associated with cyst degeneration or diffuse meningitis causing communicating hydrocephalus.
- Key Diagnostic Features:
- Imaging findings vary with the stage. The presence of cystic lesions demonstrating a scolex (seen in the vesicular or colloidal vesicular stage) can be considered pathognomonic. The scolex is visualized as a bright nodule within the cyst, producing a “hole-with-dot” appearance.
- Signal intensity of the cyst is slightly different from that of CSF, usually without enhancement in the vesicular (quiescent) stage. As the larvae begin to degenerate (colloidal vesicular stage), surrounding edema develops and there is typically ring enhancement of the cyst wall.
- Differential Diagnoses:
- colloid cyst: usually brightly hyperintense on T1 images; absence of scolex
- ependymal cyst and choroid plexus cyst: cystic but without a scolex
- intraventricular epidermoid cyst: shows restricted diffusion; absence of scolex
- arachnoid cyst: suppresses completely with FLAIR; absence of scolex
- Treatment:
- Treatment options include surgery, cysticidal agents, and corticosteroids and should be individualized on the basis of clinical presentation, location, and the evolutionary stage of cysts. Endoscopic or open microsurgical removal of cysts should be considered if there is mass effect, CSF obstruction, or fourth ventricular cysts, or if the diagnosis is uncertain.
- There is a possibility of the cyst migrating in the ventricular system between the time of diagnosis and surgery. Repeat imaging done just prior to the surgery may prevent unnecessary exploration.
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