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 prote in concentration within the contents and the variable radiological appearan ce on CT and MRI. Methods and patients: We present a case of an extraaxial epithelial cyst with changing CT and MR characteristics. Results: The appea rance of our cyst on CT or MRI changed with size and morphology. When CT st udies showed an hypodense cyst, the lesion was large but when an hyperdense mass was present, the lesion was smaller. In the later situation MRI showe d hyperintensity on T1-weighted images and hypointensity on T2-weiehted ima ges and the protein concentration of the cystic contents was high. Conclusi ons: We believe that a relatively high protein concentration in our cyst wa s 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 conc entration within the cyst. (C) 2001 Elsevier Science Ireland Ltd. All right s reserved.