MAGNETIC-RESONANCE-IMAGING - AN ACCURATE METHOD TO EVALUATE ARTERIOVENOUS-MALFORMATIONS AFTER STEREOTAXIC RADIOSURGERY

To determine the accuracy of magnetic resonance (MR) imaging in compar ison to cerebral angiography after radio-surgery for an arteriovenous malformation (AVM), the authors reviewed the records of patients who u nderwent radiosurgery at the University of Pittsburgh Medical Center b efore 1992. All patients in tile analysis had AVMs in which tile flow- void signal was visible on preradiosurgical MR imaging. One hundred si xty-four postradiosurgical angiograms were obtained in 140 patients al a median of 2 months after postradiosurgical MR imaging (median 24 mo nths after radiosurgery). Magnetic resonance imaging correctly predict ed patency in 64 of 80 patients in whom patent AVMs were seen on follo w-up angiography (sensitivity 80%) and angiographic obliteration in 84 of 84 patients (specificity 100%). Overall, 84 of 100 AVMs in which e vidence of obliteration was seen on MR images displayed angiographic o bliteration (negative predictive value. 84%), Ten of the 16 patients w ith false-negative MR images underwent follow-up angiography: in seven the lesions progressed to complete angiographic obliteration without further treatment. Exclusion of these seven patients from the false-ne gative MR imaging group increases the predictive value of a negative p ostradiosurgical MR image from 84% to 91%. No AVM hemorrhage iv as obs erved in clinical follow up of 135 patients after evidence of oblitera tion on MR imaging (median follow-up interval 35 months; range 2-96 mo nths; total follow up 382 patient-years). Magnetic resonance imaging p roved to be an accurate, noninvasive method for evaluating the patency of AVMs that were identifiable on MR imaging after stereotactic radio surgery. This imaging modality is less expensive, more acceptable to p atients, and does not have the potential for neurological complication s that may be associated with cerebral angiography. The risk associate d with follow-up cerebral angiography may no longer justify its role i n the assessment of radiosurgical results in the treatment of AVMs.