Introduction: A case of safely treated parasellar cyst by endoscopic fenestration of the third ventricular floor from outside of the ventricle to establish communications between the cyst and the ventricle is reported.
Materials and methods: During the endoscopic procedures, the anterior commissure and the foramina of Monro could be clearly observed using this approach.
Conclusion: In treating parasellar cysts with thick walls, endoscopic fenestration of the third ventricular floor in the reverse direction, i.e., from inside of the cyst, should be considered.