Role of the constructive interference in steady-state sequence in the classification of sacral meningeal cysts.

Abstract

To investigate the role of the CISS (constructive interference in steady state) sequence in sacral meningeal cysts. Fourteen patients with sacral meningeal cysts were included. Conventional T1W and T2W sequences and the CISS sequence (TR/TE = 12.25/5.90) were obtained at 1.5-T. The 1-mm-thick base images and multiplanar reformatted images of the CISS sequence were studied. The sacral meningeal cysts were classified by the CISS sequence in accordance with the previously described surgical and histopathological criteria. A total of 25 sacral meningeal cysts were identified in the 14 patients. The cysts and their contents were visualized by the CISS sequence, and the CISS sequence was superior to the T1W and T2W images. Fifteen of the cysts were consistent with type I lesions (extradural meningeal cysts without nerve fibers inside) and 10 cysts with type II lesions (extradural meningeal cysts with nerve fibers inside). There were no type III lesions (intradural meningeal cysts) in the sacral region. Previous studies have indicated that conventional MRI as well as magnetic resonance myelography are inconsistent for a classification of sacral meningeal cysts. The CISS sequence with its capability to obtain T2W thin slice acquisitions is superior in showing the nerve root fibers contained in the cysts, which is essential in the differentiation of type I and II cysts. Application of the CISS sequence is recommended in the diagnosis of sacral meningeal cysts.