[Third ventriculostomy for obstructive hydrocephalus: findings in radioisotope cisternography]

To study the findings in radionuclide cisternography in patients with obstructive hydrocephalus following third ventriculostomy.

Lumbar radionuclide cisternography was performed in 15 patients with obstructive hydro- cephalus before and after third ventriculostomy.

The postoperative cisternography identified radiopharmaceutical reflux into the lateral cerebral ventricles with delayed clearance for 24 h, similar to the findings by cisternography of communicating hydrocephalus.

The cause of ventricular radiopharmaceutical reflux is not yet understood, possibly in association with the reversal of normal cerebrospinal fluid flow though the fenestration on the third ventrical floor.