Neurocysticercosis (NCC)
- Background
- Neurocysticercosis (NCC) is the most common parasitic infection of the central nervous system.
- MR imaging is very helpful in diagnosis, as serological tests can have significant false negative rates.
- Clinical Presentation
- Patients can present with headaches related with parenchymal disease mass effect, or with hydrocephalus due to intraventricular or racemose disease.
- Parenchymal disease is also associated with seizures.
- Intraventricular disease is associated with a higher morbidity and mortality.
- Racemose subarachnoid disease will present with meningitis, vasculitis, and/or hydrocephalus as well.
- Generally, patients are asymptomatic during the vesicular stage, until the larva degenerates.
- Key Diagnostic Features
- Up to 33% of cases are intraventricular, especially in the fourth ventricle, associated with non-communicating hydrocephalus.
- In this case, the patient had a cyst in the fourth ventricle that was found to have an alive scolex during surgery.
- Typical appearance: Cystic lesion with a nodule that is most diagnostic of a scolex when hyperintense on DWI. The 4 stages can overlap in the same patient:
- Vesicular Stage: Scolex is a mural nodule within a cystic lesion that usually does not enhance; the scolex is best confirmed when restricts on DWI, thought to be due to early cyst degeneration, genetic variations of the parasite, or host immune response.
- Colloid Vesicular Stage: Larva degenerates; host inflammatory response is associated with perilesional edema and rig enhancement.
- Granular Nodular Stage: Parasite dies; the cyst wall retracts and perilesional edema decreases.
- Nodular Calcified Stage: Calcification of the healed nodule.
- Differential Diagnosis (with imaging features that can be used to distinguish from NCC):
- Pyogenic abscess: Thin enhancing wall, strong restricted diffusion, dual GRE/SWI hypointense rim sign.
- Cystic tumors with enhancing mural nodule: Pilocytic astrocytoma (cerebellar in children) and hemangioblastoma (posterior fossa in adults); the enhancing nodule may have flow voids in these cases.
- Arachnoid cyst: Extra-axial, isodense/isointense to CSF in all sequences, nonenhancing, without mural nodule.
- Other parasitic infections: Hydatid cyst does not have scolex.
- Ventricular CSF pulsation artifact: On fast FLAIR, patients with aging or ventriculomegaly may have intraventricular hyperintense artifacts due to ghosting effect or inversion delay; these artifacts can resolve on perpendicular sagittal views and may not be visible in any other sequence.
- Treatment
- Albendazole and surgery are the accepted treatments for NCC.
