Neurocysticercosis is caused by infection with the pork tapeworm Taenia solium, and undergoes specific clinical and imaging changes at it progresses through four stages of infection.
1. Vesicular - viable parasite with intact membrane and therefore no host reaction. Cyst is CSF density / intensity, and a hyperintense scolex on T1WI can sometimes be seen. No enhancement is typical, although very faint enhancement of the wall and enhancement of the scolex may be seen.
2. Colloidal vesicular - parasite dies and the cyst fluid becomes turbid (hyperdense and hyperintense on T1WI). As the membrane becomes leaky oedema surrounds the cyst and the wall becomes thickened and brightly enhances - scolex can often still be seen as an eccentric focus of enhancement.
3. Granular nodal - Oedema decreases as the cyst retracts further. Enhancement persists.
4. Nodular calcified - endstage quiescent calcified cyst remnant. No oedema.
For more information about neurocysticercosis, a photo of a scolex and DDx please visit Radiopaedia.org here.
Reference: Osborn A. et al. Diagnostic imaging: Brain. Amirsys 2004
Credit: Dr Frank Gaillard