Clinically silent choroid plexus cyst: evaluation by diffusion-weighted MRI

We retrospectively reviewed diffusion-weighted magnetic resonance images of 57 patients with a choroid plexus cyst diagnosed by contrast-enhanced T1-weighted imaging. All the cysts appeared to represent incidental findings. Thirty-eight of 57 patients had bilateral cysts and 19 had unilateral ones. On diffusion-weighted images, 78 of 95 cysts showed homogeneously high signal intensity, 12 showed focal high signal areas, and 5 had no portion with a high signal. The apparent diffusion coefficient of the high signal areas in the cysts was (1.46±0.14) ×10⁻³ mm²/s, intermediate between the apparent diffusion coefficients of cerebrospinal fluid and cerebral white matter, (3.15±0.67) ×10⁻³ and (0.79±0.22) ×10⁻³ mm²/s, respectively. Pathological correlation was available in one case, showing high signal intensity areas in the glomera of the choroid plexuses in the lateral ventricles on diffusion-weighted images corresponding to gelatinous cysts with highly proteinaceous content.