- Two main types – cystic and alveolar. Cystic more common
- Definitive host – dog
- Intermediate host – sheep and cattle
- Accidental host – man
- Infected via feco-oral transmission
- CNS involvement in 4% of cases
- Hematogenous spread of embryos from gastrointestinal tract
- Large, isolated, unilocular, well-defined and thin-walled cysts
- Small daughter cysts arranged peripherally within large maternal cyst – pathognomonic of hydatid cyst
- Cyst fluid follows CSF signal/density
- Active cysts: thin rim of enhancement and mild perilesional edema
- Late stage: calcification may be seen, dead cyst
- Alveolar form: high mortality rate, numerous irregular small cysts. Heterogeneous, nodular or cauliflower like enhancement
El-Shamam, Omran, Talal Amer, and Mohamed Abo El-Atta. “Magnetic resonance imaging of simple and infected hydatid cysts of the brain.” Magnetic resonance imaging 19.7 (2001): 965-974.
Pedrosa, Iván, et al. “Hydatid Disease: Radiologic and Pathologic Features and Complications 1: (CME available in print version and on RSNA Link).” Radiographics 20.3 (2000): 795-817.