Isolated fourth ventricular cysticercus cyst: MR imaging in 4 cases with short literature review.

We describe the magnetic resonance imaging (MRI) signal characteristics of isolated (solitary lesion) intra fourth ventricular cysticercus cyst in 4 patients who clinically presented with obstructive hydrocephalus. All patients had routine MRI sequences (T1, T2, & proton density-weighted imaging), Fluid Attenuation Inversion Recovery (FLAIR), and post-gadolinium imaging followed by cerebrospinal fluid (CSF) flow study. It revealed a CSF signal intensity (on all pulse sequences), intra fourth ventricular cyst with a nidus (scolex), and wall enhancement. On T1-weighted and FLAIR images, the cyst wall and nidus (scolex) were seen in 3 cases, which were not seen in other routine sequences. The CSF flow study showed the intraluminal nature of the cyst. The MRI features suspected a cysticercus cyst, and per-operative findings and histopathological examination confirmed the diagnosis. The review of literature of the intra fourth ventricular cyst is briefly discussed.