Specific Imaging Findings

The vesicles in this racemose type of neurocysticercosis (NCC) are extra-axial and may be located throughout the CSF-containing spaces. Fluid in racemose cysts has CT attenuation values and MR signal properties closely paralleling CSF. Intraventricular cysticerci can cause rapidly progressive and potentially fatal non-communicating hydrocephalus but are typically not seen on standard CT and MR imaging studies. Racemose cysts lack the usual scolex and are seen as single or, more commonly, multilobulated cystic masses, best depicted on 3D high-resolution heavily T2-weighted images (CISS, DRIVE, FIESTA, etc.). FLAIR images obtained following continuous inhalation of 100% oxygen show increased signal intensity of the CSF, leading to much better conspicuity of cyst walls, because the cyst contents do not increase in signal. A thin subependymal or subpial rim of high T2 signal due to inflammatory tissue reaction may be present along with a thin peripheral contrast enhancement. The subarachnoid cysts may also lead to vasculitis of the adjacent arteries and associated infarcts. MR spectroscopy demonstrates presence of lactate and a large resonance at 2.4 ppm corresponding to pyruvate within racemose NCC cysts.