SIGNIFICANCE OF MRI CHANGES AFTER SURGERY OF THE SKULL BASE

Magnetic resonance (MR) imaging is commonly used in the followup of pa tients who have undergone surgical removal of tumors from the cranial base to assess the possibility of tumor recurrence, persistence, or su rgical complications. Interpretations of this study must be cautious b ecause postoperative enhanced signals are encountered frequently. Alth ough technological improvements continue to enhance the usefulness of MR images for followup, problems remain in differentiating between fib rotic, reconstructive changes, and tumor recurrence. In this study, th e hospital records and MR findings of 215 patients who had undergone s kull base surgery were reviewed. The study was prompted by negative op erative exploration in three patients in whom postoperative MR images strongly suggested tumor recurrence. One-year follow-up images were av ailable in 174 patients. Of these, 94% showed signal enhancement on th e 1-year follow-up study. Progressive changes were observed in 14% of patients. The correlation of preoperative MR findings and surgery, wit h regard to dural involvement, vascular involvement, cranial nerve inf iltration, and extent of intracranial infiltration, was analyzed in 28 patients. Methods to facilitate the detection of tumor recurrence usi ng MR images are reviewed.