Aim:To investigate the preoperative, early and late postoperative differences in the anterior callosal angle, lateral and third ventricle shapes of patients with pituitary macroadenoma operated via the transsphenoidal approach.Material and Methods:: Shape data of the third and lateral ventricles were collected from the two-dimensional digital images. The generalised Procteus analysis was used to obtain mean shapes in the preoperative, early and late postoperative phases. The shape deformation of the ventricles from pre-to postoperative phases was evaluated using the thin plate spline method. Anterior callosal angle (ACA) was measured pre-to postoperative images and was analyzed statistically.Results:There was no significant lateral ventricle shape and ACA measurement difference in the pre and postoperative phases. The high-level deformations from the pre- to postoperative phase were seen in thin plate spline graphs. The highest deformation was observed at the third ventricle. Third ventricle deformation continued from the early to the late postoperative period, but this deformation is more limited than in preoperative comparisons.Conclusion:In this study, we demonstrated that shape changes in the third ventricle of patients with pituitary macroadenoma persisted during the postoperative period through statistical geometric morphometric shape analysis. This phenomenon may result from dysfunction of the ventricular surface cilia due to chronic tumor compression and surgery-related neurotrauma. Additionally, we identified the diagnostic limitations of ACA in patients without radiological signs of hydrocephalus.