Female, 3 years old, with arachnoid cyst. A cystic lesion is redemonstrated which seems to originate in the right aspect of the quadrigeminal plate cistern and which follows CSF on all sequences. The lesion measures no more than 21 x 16 mm in the axial plane showing no increase in size from the prior examination. The lesion causes mild mass effect upon the adjacent right thalamus, and causes leftward displacement of the pineal gland and internal cerebral veins.Brain parenchymal morphology is otherwise within normal limits. No areas of pathologic signal abnormality are seen. No parenchymal edema is detected. There are no findings to suggest intracranial hemorrhage. The ventricular system is otherwise normal in size. A normal variant cavum vergae is noted.
Stable appearance of a cystic lesion centered on the right quadrigeminal plate cistern which is favored to represent an arachnoid cyst.