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 how after third ventriculostomy. In this s tudy, we attempted to confirm the accuracy of cine PC MR imaging for determ ining the patency of a third ventriculostomy as compared with direct reexpl oration of the floor of the third ventricle. METHODS: We examined II patients with third ventriculostomies who had a tot al of 13 reoperations for symptomatic obstructive hydrocephalus. In 12 of t he 13 reexplorations, cine PC MR studies were obtained before repeat surger y, and the diagnoses suggested by imaging were compared with intraoperative findings. RESULTS: Four of five patients who had no how on MR images had new membrane s that covered the orifice; the fifth patient still had a small perforation visible at the time of operation. Three of four patients who bad subtle ho w 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 vent riculostomy had completely open perforations without membrane formation; th e third patient had nonobstructive early membrane formation, At 3 months' f ollow-up, two flow studies were read as subtle without any clinical symptom s; however, these eventually progressed to become symptomatic, and occlusio n with new membrane formation was con firmed during surgical reexploration. CONCLUSION: Cine PC MR imaging is a reliable technique for detecting the pa tency of a third ventriculostomy, but minor flow, as defined in this report , appears to be an early sign of closure.