Introduction: There is no established criteria in the application of an image-based definitive diagnosis for cystic lesions of the sella turcica. Rathke’s cleft cysts are the most common non-neoplastic intrasellar lesions. To our knowledge, this is the first report of an intrasellar CSF cyst without membrane, capsule or any other lining.

Case Report: A 19-year-old male presented an incidental finding of a possible intrasellar cyst in cranial CT scan following a cranioencephalic traumatism. Cranial MRI showed a 22 x 20 mm cystic lesion with sellar widening and optic chiasm compression, compatible with Rathke’s cleft cyst. The endoscopic transsphenoidal approach consisted of CSF cyst evacuation and reconstruction of the sellar floor to avoid a postoperative CSF leak, finding a fine grayish sheet of glandular tissue partially surrounding the CSF intrasellar cavity. Surgical inspection revealed a CSF leakage through the middle part of the pituitary gland arising from the third ventricle or suprasellar cisterns. Very small fragments of pituitary gland in contact with the CSF cyst were sent for pathological study; however, the absence of any cystic wall with unaltered pituitary gland tissue was reported. There was no postoperative CSF leakage, although the patient developed panhypopituitarism.

Discussion: This case is described as an intrasellar CSF cyst without membrane secondary to an intrapituitary fistula. We hypothesize the CSF accumulation was due to CSF flow along a congenital connection developed from the third ventricle or suprasellar cisterns through the pituitary gland into the sellar region.