Object: In this paper, the authors' goal was to determine whether benign pineal cysts have smooth walls or internal structure on high-resolution MR imaging and to evaluate their imaging characteristics on FLAIR images.
Methods: The authors retrospectively reviewed the MR imaging findings in 60 consecutive patients who were reported to have pineal cysts over a 19-month period. Patients were identified retrospectively using a word search of radiology reports. Of these 60 patients, 24 with stable follow-up imaging or pathological proof of a pineal cyst were included in this study. In all cases, axial or sagittal FLAIR images were available, and in 10 of 24 patients the authors obtained sagittal images using fast imaging employing steady-state acquisition (FIESTA). For those cases in which FIESTA studies were obtained, the authors classified the cysts into 1 of 4 categories based on their appearance. Eighteen of 24 cases were performed with intravenous contrast.
Results: Of the 24 cases, 21 had signal intensity on FLAIR images that differed from that of CSF. Of the 10 cases with FIESTA, 6 had evidence of internal structure within the pineal cyst. The authors found it of interest that 20 of the 24 patients were female.
Conclusions: Although the presence of a thin wall supports the diagnosis of a benign pineal cyst, fine internal septations or small internal cysts are common on high-resolution MR imaging and this finding should not be considered evidence of an underlying tumor. It is typical for pineal cysts to have relaxation times that differ from CSF as determined by FLAIR imaging.