Changes in Cyst Volume following Intraoperative MRI-Guided Ommaya Reservoir Placement for Cystic Craniopharyngioma

Abstract

Introduction: Intracavitary treatment of solitary cystic craniopharyngiomas with ³²P is an emerging treatment option, especially for pediatric patients. We have treated two patients with solitary cystic craniopharyngiomas using intraoperative MRI (iMRI)-guided catheter placement. Methods: The optical tracking system of the General Electric Signa SP iMRI system was utilized for preoperative planning and intraoperative catheter tracking during insertion. Intraoperative volumetric imaging was then used to confirm final catheter position. Patients were brought back to the iMRI suite approximately 8 weeks later and diluted gadolinium was injected with further MRI to confirm the absence of communication between the cyst lumen and surrounding CSF spaces and for volumetric analysis. Results: Intraoperative imaging illustrated deformation and changes in the cyst wall during catheter placement and cyst aspiration and confirmed final catheter placement. Images acquired 8 weeks following catheter placement prior to the instillation of ³²P showed decreases in cyst volume of 40 and 85%. Conclusion: iMRI-guided catheter placement for cystic craniopharyngiomas helps to assure successful catheter placement. Significant decreases in cyst volume occur in the interval between catheter placement and ³²P administration and must be accounted for to prevent overdosing of the radioisotope.