Unusual changing CT and MR appearance of an epithelial intracranial cyst

Introduction: Epithelial cysts are infrequent intracranial lesions and may content cilia and mucosecretant cells that may be responsible for the protein concentration within the contents and the variable radiological appearance on CT and MRI. Methods and patients: We present a case of an extraaxial epithelial cyst with changing CT and MR characteristics. Results: The appearance of our cyst on CT or MRI changed with size and morphology. When CT studies showed an hypodense cyst, the lesion was large but when an hyperdense mass was present, the lesion was smaller. In the later situation MRI showed hyperintensity on T1-weighted images and hypointensity on T2-weiehted images and the protein concentration of the cystic contents was high. Conclusions: We believe that a relatively high protein concentration in our cyst was the major factor for the high attenuation on CT and the hyperintensity or hypointensity on T1- and T2-weighted images. respectively. We believe than these atypical imaging findings were caused by changes in the protein concentration within the cyst. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.