Space occupying cystic lesion occupying most of the right lateral ventricle with content mildly FLAIR hyperintense compared to CSF is noted. It has a thin smooth wall, without suspicious nodularity or enhancement or susceptibility. The septum pellucidum is shifted to the left by 10 mm. The choroid is displaced to the right. The right temporal horn is moderately dilated comparison to the left, suspicious of some degree of trapping. The remainder of the examination is remarkable--minimal FLAIR hyperintense foci in the white matter and within age-appropriate limits.
Conclusion: Right lateral ventricular simple appearing cystic lesion almost certainly represents an intraventricular arachnoid/neuroepithelial cyst.