Unique MR spectroscopic finding in colloid-like cyst

Cysts morphologically identical to colloid cysts are rarely reported to be located in areas outside the third ventricle. We report the magnetic resonance (MR) imaging and spectroscopic findings in three patients with colloid like cyst located in the ponto-medullary, pre-pontine cistern and suprasellar region. The MR imaging and spectroscopy performed on a 1.5-tesla scanner in three female patients revealed T1 hyperintense mass lesions. A large dominant metabolite peak at 2.0-ppm chemical shift, simulating N-acetylaspartate (NAA) of normal neuronal tissue was detected within the lesion.This peak is probably due to the presence of glycoproteins secreted by the ciliated columnar epithelium lining these cysts. MR spectroscopy of colloid cyst has not been described in the literature and hence the findings in this study will help in the diagnosis of this cystic lesion especially when located at unusual location. The signal characteristics of these cysts in various sequences including diffusion weighted imaging (DWI) and susceptibility weighted imaging (SWI) are also discussed. (orig.)