Postoperative radiographic findings in patients undergoing intracranial electrode monitoring for medically refractory epilepsy

Abstract

Object In this study the authors sought to determine whether any correlations existed between postimplantation head CT findings and the need to perform decompression surgery in patients with grid electrodes. Methods The authors identified 74 patients who underwent intracranial electrode monitoring for medically refractory epilepsy from January 2000 through June 2008. Only the 46 patients who had head CT scans available for review were included in the study. The authors were able to determine the number and types of electrodes placed as well as complications experienced. They reviewed the CT scans for abnormal findings including extraaxial fluid collections, intracranial hemorrhages, and signs of mass effect. Results All patients developed some degree of extraaxial fluid collection following the placement of intracranial electrodes. The maximum width of the extraaxial fluid collection and the degree of midline shift were not predictive of the need for decompressive surgery. The presence, but not degree, of midline shift was associated with the need for decompressive surgery. Likewise, the presence of ventricular asymmetry was correlated with the need for removal of the electrodes and bone flap. Patients without midline shift or ventricular asymmetry on CT did not require decompressive surgery. Conclusions After undergoing placement of intracranial electrodes all patients develop extraaxial fluid collections. In addition, many patients develop signs of mass effect including midline shift and ventricular asymmetry. When these findings are absent it is highly unlikely that surgical decompression is required.