 There is a 59 x 54 mm sagittal dimension homogeneously CSF signal intensity posterior fossa cyst without enhancement. There is associated adjacent bone remodeling and minimal mass effect on the cerebellum. Lesion extends from the cisterna magna into the superior cerebellar cistern. There is no diffusion abnormality associated with this lesion.The pituitary gland is normal in size. However, there is a 7 x 9 mm focus of intrinsic T1 hyperintense signal in the posterior and inferior aspect of the pituitary gland (series 401 image 12) which is larger than what is expected for a normal neurohypophysis. This may represent a proteinaceous Rathke's cleft cyst. There is no focus of susceptibility effect to suggest prior hemorrhage. There is no deviation of the pituitary stalk, effacement of the suprasellar cistern or mass effect on the optic chiasm.There is no suspicious intracranial enhancement, acute infarct, or cerebral edema. The ventricles and basal cisterns are normal in size and configuration. There is no hydrocephalus. There is no midline shift or herniation.
1.Findings consistent with an arachnoid cyst in the posterior fossa with minimal local mass effect.2.Normal sized pituitary gland with a prominent 7 x 9 mm focus of intrinsic T1 hyperintensity in its posterior and inferior aspect which is favored to represent a Rathke's cleft cyst with proteinaceous material. No associated mass effect.3.No evidence of intracranial traumatic injury.I personally reviewed the Images and/or procedure with the Resident/Fellow and agree with this report.