Persisting intrapituitary recessus infundibuli.

X-ray examination of the intracranial ventricles with Dimer X made it possible to make the diagnosis of obstructive hydrocephalus due to a mass lesion of the midbrain and abnormal intrasellar recess of the third ventricle in a 34 year old female patient. Considering the location and ontogenetic and phylogenetic facts one can diagnose the second pathological finding as a persisting intrapituitary recessus infundibuli. A malformation due to inhibition during development is to be assumed.