Identification of Disappearing Brain Lesions With Intraoperative Magnetic Resonance Imaging Prevents Surgery

BACKGROUND: Typically, neurosurgery is performed several weeks after diagnostic imaging. In the majority of cases, histopathology confirms the diagnosis of neoplasia. In a small number of cases, a different diagnosis is established or histopathology is non-diagnostic. The frequency with which these outcomes occur has not been established. OBJECTIVE: To determine the frequency and outcome of disappearing brain lesions within a group of patients undergoing surgery for suspected brain tumor. METHODS: Over the past decade, 982 patients were managed in the intraoperative magnetic resonance imaging unit at the University of Calgary, Alberta, Canada. These patients have been prospectively evaluated. RESULTS: In 652 patients, a brain tumor was suspected. In 6 of the 652 patients, histopathology indicated a nontumor diagnosis. In 5 patients, intraoperative images, acquired after induction of anesthesia, showed complete or nearly complete resolution of the suspected tumor identified on diagnostic magnetic resonance imaging acquired 6 +/- 4 (mean +/- SD) weeks previously. Anesthesia was reversed, and the surgical procedure aborted. The lesions have not progressed with 6 +/- 2 years of follow-up. CONCLUSION: Intraoperative magnetic resonance imaging prevented surgery on 5 patients with disappearing lesions.