Successful delivery of intraventricular radioimmunotherapy is contingent on adequate CSF flow. The authors present a patient with medulloblastoma in whom obstructed CSF flow was causing hydrocephalus, which was initially corrected by implantation of a programmable shunting device. While managing the hydrocephalus, an endoscopic third ventriculostomy (ETV) needed to be performed in a collapsed ventricular system to ensure adequate radioimmunotherapy distribution.
This 18-month-old patient with medulloblastoma involving leptomeningeal dissemination presented for intraventricular radioimmunotherapy. A CSF 111In-DTPA scintigraphy study obtained through the existing programmable ventriculoperitoneal shunt demonstrated activity in the lateral and third ventricles, but no activity over the cerebral convexities or spinal canal, consistent with obstruction at the level of the cerebral aqueduct. By maximization of ventricular size in a controlled setting, the patient was able to undergo a trial of ETV through very small ventricles. A postoperative CINE MR imaging study confirmed patent ETV. The pressure settings on the shunt were kept at the highest opening pressure (200 mm H2O) to maximize flow through the stoma and improve the distribution of CSF throughout the subarachnoid space. The CSF flow scintigraphy study was again performed, this time with tracer activity demonstrated down the thecal sac at 3 hours, and symmetrically over the cerebral convexities at 24 hours. The patient began weekly intraventricular administration of 131I-3F8 therapy.
Successful rerouting of CSF flow for the purpose of therapeutic radioisotope administration is possible. Endoscopic third ventriculostomy can be considered in patients with programmable shunting devices; normal or slit ventricles do not preclude successful ETV.