[MR imaging study of edema along the optic tract in patient with Rathke's cleft cyst]

We report an 80-year-old woman who was admitted to our hospital with symptoms due to diabetes insipidus. Magnetic resonance (MR) imaging demonstrated a sellar/suprasellar cystic lesion with marginal enhancement and the thick pituitary stalk. The MR imaging depicted edema spreading along the optic tract on fluid-attenuated inversion recovery (FLAIR) images. Upon neurological examination at the time of admission, there were no abnormal findings affecting the field of vision or visual acuity. In endocrinological examination, the basal plasma values of pituitary hormones were within normal range except for that of prolactin, which was 47.9 ng/ml. The preoperative diagnosis was craniopharyngioma, and the intrasellar mass was partially removed by the endoscopic transnasal transsphenoidal approach. Postoperative histopathological examination revealed Rathke's cleft cyst associated with squamous metaplasia. Lymphocytic infiltration was also confirmed in both the anterior and posterior pituitary lobe. The postoperative course was satisfactory. Edema spreading along the optic tract was reported as a characteristic MR imaging finding for diagnosis of craniopharyngiomas or optic nerve glioma. However, it is suggested that edema of the optic pathway seems to be caused not only by craniopharyngioma but also other suprasellar lesions. It was a rare case of secondary lymphocytic hypophysitis caused by Rathke's cleft with edema along the optic tract.