Fax +41 61 306 12 34 E-Mail karger@karger.ch www.karger.com Technical Note Pediatr Neurosurg 2010;46:71–75 DOI: 10.1159/000315321 A Novel Method for Confirmation of Hemispheric Disconnection during Hemispherotomy Surgery Daniel L. Kim   a–c Leisha L. Osburn   a Aaron A. Cohen-Gadol   a–c   a  Clarian Neuroscience, b  Goodman-Campbell Brain and Spine, and c  Department of Neurological Surgery, Indiana University, Indianapolis, Ind., USA Introduction Hemimegalencephaly is a rare congenital malforma- tion of cortical development characterized by the dys- plastic hypertrophy of one cerebral hemisphere from ab- normal neuronal and glial proliferation. The classic triad of neurologic findings associated with hemimegalen- cephaly includes psychomotor retardation, contralateral motor deficit, and medically refractory epilepsy. The ep- ilepsy associated with hemimegalencephaly is the over- riding and disabling symptom of this disorder, and it is of a severity that often justifies early surgical treat- ment [1]. Because the epileptic focus is the abnormal hemi- sphere, surgical intervention must provide a complete disconnection of the epileptogenic hemisphere from the normal contralateral hemisphere. Functional disconnec- tion via hemispherotomy has been previously described and entails (1) removal of the medial temporal lobe struc- tures, (2) disruption of the fibers through the corona ra- diata and internal capsule, (3) intraventricular corpus callosotomy, and (4) disconnection of the frontal hori- zontal fibers [2, 3]. We present a method that could po- tentially confirm complete hemispheric disconnection as a predictor of postoperative seizure outcome by using in- Key Words Hemispherotomy  Electroencephalography  Hemispheric disconnection  Epilepsy Abstract Background/Aims: Hemispherotomy has become a safe and effective surgical option for patients suffering from in- tractable epilepsy associated with diffuse unihemispheric malformations of cortical development. However, as com- pared to hemispherectomy, hemispherotomy, by leaving brain tissue behind, may leave some hemispheric connec- tions intact, therefore increasing the risk of postoperative seizures. This is especially important to consider in the case of the highly epileptogenic hemisphere in hemimegalen- cephaly. Methods: The authors use intraoperative electro- encephalography (EEG) on the ipsilateral occipital lobe and contralateral hemisphere to confirm complete hemispheric disconnection during hemispherotomy surgery. Results: This technique has been successful in the confirmation of hemispheric disconnection as no patient has had recurrence of his/her seizure postoperatively. Conclusion: Intraopera- tive EEG may be a useful tool to confirm hemispheric discon- nection during hemispherotomy. Copyright © 2010 S. Karger AG, Basel Received: October 12, 2009 Accepted after revision: February 15, 2010 Published online: June 1, 2010 Aaron A. Cohen-Gadol, MD, MSc Goodman-Campbell Brain and Spine Department of Neurological Surgery, Indiana University 1801 North Senate Blvd No. 610, Indianapolis, IN 46202 (USA) Tel. +1 317 362 8760, Fax +1 317 924 8472, E-Mail acohenmd  @  gmail.com © 2010 S. Karger AG, Basel 1016–2291/10/0461–0071$26.00/0 Accessible online at: www.karger.com/pne