venerdì 22 gennaio 2010
Neurocysticercosis (Calcified stage)
CT with contrast images showed a 7 mm calcified enhancing lesion within the posterior aspect of the left frontal lobe with a small amount of surrounding oedema. MRI images confirm the presence of a calcified ring enhancing lesion within the left posterior frontal lobe.
Cysticercosis is caused by larvae of the pork tape worm Taenia solium. Infestation occurs via the fecal-oral route. It is the most common parasitic infection involving the central nervous system in developing countries with 90% of patients present with seizures. Parenchymal cysticercosis is the most common type with lesions most commonly being peripherally distributed near the grey-white matter junction. The parasite goes through different stage of involution, each of which has different imaging features on CT and MRI.
These include the following:
- Vesical stage: CT shows hypodense non enhancing lesions. On MRI cysts follow CSF signal; T2 hyper intense scolex may be seen. No edema. Usually no enhancement.
- Colloidal stage: CT shows hypodense/isodense lesion with peripheral enhancement and perilesional edema. On MRI Cysts are hyperintense to CSF; surrounding edema, cyst wall enhances.
- Granular stage: CT shows nodular enhancing lesions. On MRI the cyst wall thickens and retracts, there is a decrease in edema, and there is nodular or ring enhancement.
- Calcified stage: When the parasite dies, nodular parenchymal calcifications are seen. These findings are best seen on CT.