Third ventriculostomy patency: Comparison of findings at cine phase- contrast MR imaging and at direct exploration

BACKGROUND AND PURPOSE: Two-dimensional phase-contrast (PC) MR imaging is a known method for evaluating CSF flow after third ventriculostomy. In this study, we attempted to confirm the accuracy of cine PC MR imaging for determining the patency of a third ventriculostomy as compared with direct reexploration of the floor of the third ventricle. METHODS: We examined 11 patients with third ventriculostomies who had a total of 13 reoperations for symptomatic obstructive hydrocephalus. In 12 of the 13 reexplorations, cine PC MR studies were obtained before repeat surgery, and the diagnoses suggested by imaging were compared with intraoperative findings. RESULTS: Four of five patients who had no flow on MR images had new membranes that covered the orifice; the fifth patient still had a small perforation visible at the time of operation. Three of four patients who had subtle flow on MR images were found to have occlusion with new membranes; the fourth had an incomplete new membrane. Finally, two of three who had a patent ventriculostomy had completely open perforations without membrane formation; the third patient had nonobstructive early membrane formation. At 3 months' follow-up, two flow studies were read as subtle without any clinical symptoms; however, these eventually progressed to become symptomatic, and occlusion with new membrane formation was confirmed during surgical reexploration. CONCLUSION: Cine PC MR imaging is a reliable technique for detecting the patency of a third ventriculostomy, but minor flow, as defined in this report, appears to be an early sign of closure.