FUNCTIONAL-ANALYSIS OF 3RD VENTRICULOSTOMY PATENCY WITH PHASE-CONTRAST MRI VELOCITY-MEASUREMENTS

Our purpose was to explore the utility of cine phase-contrast MRI velo city measurements in determining the functional status of third ventri culostomies, and to correlate the quantitative velocity data with clin ical follow-up. We examined six patients with third ventriculostomies and 12 normal subjects by phase-contrast MRI, The maximum craniocaudal to maximum caudocranial velocity range was measured at regions of int erest near the third ventricular floor, and in cerebrospinal fluid ant erior to the upper pens and spinal cord on midline sagittal images, Ra tios of the velocities of both the third ventricle and prepontine spac e to the space anterior to the spinal cord were obtained. The velociti es near the third ventricular floor and in the pontine cistern were si gnificantly higher in patients than in normal subjects, but the veloci ty anterior to the spinal cord was similar between the groups. The vel ocity ratios, used to normalize individual differences, were also high er in patients than in controls. Two patients had lower velocity ratio s than their fellows at the third ventricular floor and in the pontine cistern; one required a shunt 11 months later, while in the other, wh o had a third ventricular/thalamic tumor, the lower values probably re flect distortion of the third ventricular floor. We conclude that phas e-contrast MR velocity measurements, specifically the velocity ratio b etween the high pontine cistern and the space anterior to the spinal c ord, can help determine the functional status of third ventriculostomi es.