Female, 62 years old, with left arm and leg weakness, history of a right hemispheric cystic lesion in 1994 status post removal by neurosurgery. Evidence of right parietal craniotomy is seen. A cystic lesion is present situated within the parenchyma of the posterior right frontal lobe measuring up to 6 cm in maximal diameter. The lesion consists of a large primary cystic component with two or three small adjacent cystic locules medially and superiorly. There is no evidence of edema in the surrounding parenchyma.Posteriorly, the lesion appears to extend into the precentral gyrus with compression of the central sulcus. Inferiorly and medially, the lesion extends to the lateral ventricular margin but is separated from the margin by a thin membrane of soft tissue. The signal characteristics of the lesion follow CSF on all sequences. No associated pathologic enhancement is observed.At most, there may be one small focus of nonspecific subcortical FLAIR hyperintensity within the left frontal lobe. Otherwise, no significant parenchymal signal abnormality is seen. No restricted diffusion is demonstrated. There are no findings to suggest acute intracranial hemorrhage. Ventricular size and morphology are within normal limits apart from mild mass effect on the right lateral ventricle caused by the overlying cyst. No pathologic parenchymal or extra-axial enhancement is observed.
A large cystic lesion is evident occupying the posterior aspect of the right frontal lobe. The lesion extends from the brain surface peripherally to the ventricular margin at its deep surface but it does not appear to communicate directly with the ventricular system. Given the appearance and location of the lesion, the differential would include a neuroglial cyst or arachnoid cyst as the most likely entities. There are no findings to suggest that this lesion is neoplastic or associated with a neoplasm.