EARLY POSTOPERATIVE MAGNETIC-RESONANCE-IMAGING FOLLOWING NONNEOPLASTIC CORTICAL RESECTION

Postcraniotomy residual tumor is often determined by magnetic resonanc e (MR) imaging. Magnetic resonance changes that occur in the postopera tive setting must be defined to ensure both the optimum timing of post operative image acquisition and the accurate assessment of images for residual tumor. Postoperative changes in nontumor parenchyma have prev iously been described for computerized tomography but not for MR imagi ng. In the present study, 11 patients without intracranial neoplastic disease (six females and five males with a median age of 36 years) sub mitted to MR imaging 17 to 28 hours after undergoing temporal lobectom ies for epilepsy. Four of the operations were performed with the patie nts under general anesthesia and seven under local anesthesia. Postope rative MR images (T-1-weighted, T-1-weighted gadolinium enhanced, and T-2-weighted) were reviewed. Extraaxial fluid, air, or blood was prese nt in all cases. Enhancement of the resection bed parenchyma occurred in seven (64%) of 11 patients. In three of the remaining four patients , assessment of parenchymal enhancement was obscured by extraaxial flu id collections. Dural enhancement occurred adjacent to the resection s ite in all of the cases and remotely in 73%. Eight (73%) of 11 patient s displayed enhancement of the pia-arachnoid of the ipsilateral cerebr al convexity, two (18%) of the contralateral convexity, and four (36%) of the pia-arachnoid overlying the cerebellum. Contrary to previous r eports, contrast enhancement of nonneoplastic human brain parenchyma c an occur postoperatively within 17 hours. Benign parenchymal contrast enhancement is usually linear in appearance; nonneoplastic dural and l eptomeningeal enhancement can occur both adjacent to and distant from the surgical site. Extraaxial fluid collections can hinder MR evaluati on of the resection bed.