A craniopharyngioma with spontaneous involution of a gadolinium-enhanced region on magnetic resonance imaging

BACKGROUND: It has not been reported previously that the solid enhancing portion of a craniopharyngioma has involuted without a change in cyst size. CASE DESCRIPTION: We herein report a case of a craniopharyngioma with spontaneous involution of a solid gadolinium (Gd)-enhanced region on magnetic resonance imaging (MRI). A 44-year-old female was referred to our department with a mass on MRI associated with headaches and polyuria. The images showed a suprasellar cystic lesion progressing from the posterior pituitary lobe to the right hypothalamus along the pituitary stalk. Examinations of the cerebrospinal fluid showed aseptic meningitis and a positive titer of beta-human chorionic gonadotropin (HCG-β) preoperatively. The hypothalamic lesion became enlarged over the following 3 weeks, and a biopsy of the posterior pituitary lobe was performed via the endonasal transsphenoidal approach under a preoperative diagnosis of a germ cell tumor (GCT). The histological diagnosis was a craniopharyngioma, and the patient's postoperative findings on MRI were atypical: The solid Gd-enhanced region in the hypothalamus had spontaneously decreased in size and the peritumoral edema had improved, although the biopsy site in the posterior pituitary lobe was distant from the area of shrinkage. We speculated that the involutional portion on MRI mimicking a tumor was actually the normal hypothalamus, which was abnormally enhanced due to a disruption of the blood-brain barrier caused by the craniopharyngioma. CONCLUSION: Gd-enhanced regions of parenchyma neighboring the cysts of craniopharyngioma should be carefully managed, taking into consideration the possibility of the enhancement of normal tissue.