Original Articles MRI Signal Changes in the White Matter After Corpus Callosotomy Divya S. Khurana, MD*, Richard H. Strawsburg, MD ² , Richard L. Robertson, MD ‡ , Joseph R. Madsen, MD § , and Sandra L. Helmers, MD  Magnetic resonance imaging (MRI) changes reported after corpus callosotomy include hyperintensity in the corpus callosum, perifalcine hyperintensity caused by surgical retraction, and acute changes associated with surgical complications. The authors have observed MRI signal changes in the cerebral white matter of corpus callosotomy patients that are separate from the sectioned callosum and not clearly related to surgical manipulation or injury. Brain MRI scans were retrospectively reviewed in 25 of 38 patients who underwent anterior, posterior, or total callosotomy for refractory seizures between 1988 and 1995. Nine patients had signal changes in the cerebral white matter on postoperative MRI. Six of these patients had preoperative MRI studies available for comparison, and none of the white matter signal abnormalities were evident preoperatively. T 2 prolongation or hyperintensity on proton-density images was observed in areas including the centrum semiovale, forceps major, and forceps mi- nor. Three patients had signal changes that had distinct borders extending only to the posterior limit of the callosotomy. MRI signal changes in the cerebral white matter after corpus callosotomy have not been previously reported and may represent distant effects of callosal section. Wallerian degeneration occurring in the neuro- nal processes cut during surgery could account for the signal changes. © 1999 by Elsevier Science Inc. All rights reserved. Khurana DS, Strawsburg RH, Robertson RL, Madsen JR, Helmers SL. MRI signal changes in the white matter after corpus callosotomy. Pediatr Neurol 1999;21:691-695. Introduction Corpus callosotomy is a surgical procedure that may be effective in selected patients with generalized seizures refractory to medications, especially atonic or tonic sei- zures (drop attacks) [1-4]. The goal of this surgical procedure is disruption of the propagation of epileptic discharges, rather than the resection of the epileptic focus, thereby reducing or eliminating seizures. The use of this procedure in partial-onset seizures is controversial, and results are variable among epilepsy surgery centers [2,5]. Postoperative magnetic resonance imaging (MRI) has been useful in defining the extent of callosal section after partial corpus callosotomy [6-8]. Signal changes (T 2 hyperintensity) evident in the sectioned corpus callosum have been postulated to represent anisomorphic gliosis [6]. Acute or subacute surgical complications, such as blood or fluid collection and perifalcine T 2 hyperintensity caused by retraction during surgery, have also been described [9]. Postoperative MRI signal changes were observed in the cerebral white matter of patients who have had corpus callosotomy that appear to be different from signal changes previously reported. MRI signal changes in these patients were evident in the centrum semiovale, forceps major, and forceps minor, areas that are functionally related to the corpus callosum but anatomically distinct. These changes do not appear to be related to surgical manipulation or injury and may represent degeneration of neuronal processes sectioned during callosotomy. Materials and Methods Patients undergoing corpus callosotomy for medically refractory seizures between 1988 and 1995 at Children’s Hospital, Boston were retrospectively reviewed. Medical records were reviewed for infor- mation, such as the age of the patient at the time of surgery, preoperative From the *Division of Neurology; St. Christopher’s Hospital for Children; Philadelphia, Pennsylvania; ² Department of Neurology; Children’s Hospital Medical Center; Cincinnati, Ohio; and the Departments of ‡ Radiology; § Neurosurgery; and  Neurology; Children’s Hospital; Boston, Massachusetts. Communications should be addressed to: Dr. Khurana; Division of Neurology; St. Christopher’s Hospital for Children; Philadelphia, PA 19003. Received December 7, 1998; accepted June 24, 1999. 691 © 1999 by Elsevier Science Inc. All rights reserved. Khurana et al: MRI Changes After Callosotomy PII S0887-8994(99)00082-X ● 0887-8994/99/$20.00