The midline pineal "eye": MR and CT characteristics of the pineal gland with and without benign cyst formation.

The purpose of this study was to evaluate the magnetic resonance imaging characteristics of pineal cysts and pineal calcifications and to determine the incidence of benign pineal cysts. Two-hundred-fifty magnetic resonance examinations were retrospectively examined for the incidence of pineal cysts. In addition, 60 collected cases of pineal cysts were evaluated with regard to cross sectional diameter and magnetic resonance signal characteristics. Finally, the magnetic resonance signal characteristics of pineal tissue in 50 patients were compared to companion computed tomographic scans that were scrutinized for the presence or absence of calcification. The incidence of pineal cysts as revealed by magnetic resonance imaging in this study was 10.8%. The minimal and maximal measurements ranged from a low of 2 x 2 x 2 mm to a high of 10 x 12 x 10 mm. The magnetic resonance signal intensities of pineal cyst as compared to cerebrospinal fluid were iso- or hyperintense on all magnetic resonance sequences in the majority of cases. Calcifications of the pineal gland as revealed by computed tomography tended to be isointense to gray matter if the calcifications were small and hypointense to gray matter if large on all magnetic resonance acquisitions. A careful analysis of the magnetic resonance signal characteristics enables the recognition of moderate- to large-sized pineal calcifications and their differentiation from large pineal cysts. However, small cysts of the pineal gland can be difficult or impossible to distinguish on magnetic resonance imaging from calcifications without comparison with computed tomography.