Corpus Callosotomy: a Palliative Therapeutic Technique May Help Identify Resectable Epileptogenic Foci

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provided by Elsevier - Publisher Connector Seizure (2007) 16, 545—553

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CASE REPORT Corpus callosotomy: A palliative therapeutic technique may help identify resectable epileptogenic foci

Dave F. Clarke a,*, James W. Wheless a, Monica M. Chacon b, Joshua Breier c, Mary-Kay Koenig c, Mark McManis b, Edward Castillo c, James E. Baumgartner c

a Department of Pediatrics, Division of Pediatric Neurology, Le Bonheur Comprehensive Epilepsy Program, University of Tennessee Health Science Center, Memphis, TN, USA b Cook Children’s Hospital, Pediatric Neurology, Fort Worth, TX, USA c The Texas Comprehensive Epilepsy Program, Department of Neurosurgery, University of Texas Health Science Center at Houston, Houston, TX, USA

Received 2 March 2007; received in revised form 4 April 2007; accepted 16 April 2007

KEYWORDS Summary Corpus callosotomy has a long history as a palliative treatment for Corpus callosotomy; intractable epilepsy. Identiﬁcation of a single epileptogenic zone is critical to Epilepsy surgery; performing successful resective surgery. We describe three patients in which corpus Pediatric epilepsy; callosotomy allowed recognition of unapparent seizure foci, leading to subsequent Seizure; successful resection. Intractable epilepsy We retrospectively reviewed our epilepsy surgery database from 2003 to 2005 for children who had a prior callosotomy and were candidates for focal resection. All underwent magnetic resonance imaging and scalp video electroencephalograph monitoring, and two had magnetoencephalography, electrocorticography and/or intracranial video electroencephalograph monitoring. The children were 8 and 9 years old, and seizure onset varied from early infancy to early childhood. One child had a history of head trauma preceding seizure onset, one had a large intracerebral infarct and dysplastic cortex in the contralateral frontal lobe, and the other had an anterior temporal lobe resection without improvement in seizure frequency. After medical management failed, callosotomy was performed with the expecta- tion of decreasing the seizure types affecting both hemispheres. Following transection of the callosal ﬁbers, a single focus was recognized and resected, with resultant dramatic improvement in seizure control. In medically refractory epilepsy, where rapid secondary bisynchrony is suspected but the electroencephalograph is non-localizing, callosotomy should be considered as

* Corresponding author at: Department of Pediatrics, Division of Pediatric Neurology, University of Tennessee Health Science Center, 777 Washington Ave., P.O. Box 335, Memphis, TN 38105, USA. Tel.: +1 901 287 5206; fax: +1 901 287 5325. E-mail address: [email protected] (D.F. Clarke).

a means of treating generalized seizure types, but may also assist in identifying potentially operable seizure foci. Study limitations include its retrospective nature and cohort size. The ﬁndings, however, suggest the need for prospective, systematic, well-controlled studies of the use of corpus callostomy in this intractable patient population. # 2007 British Epilepsy Association. Published by Elsevier Ltd. All rights reserved.

Introduction would be apparent that a small number of patients had a single epileptogenic focus, which would allow The corpus callosum is the principal anatomic and further resective surgery. Our experience suggested neurophysiologic track linking the cerebral cortices. this procedure might also have diagnostic utility by Neuronal signaling is transmitted across this vast clarifying which patients with rapid secondary gen- network of axons to the contralateral homotopic eralization have independent epilepsy generators regions. Bisynchrony of epileptiform discharges from either hemisphere or a single epileptogenic occurs primarily via this network of fibers traversing zone. the corpus callosum. Generation of generalized or secondarily generalized seizures is dependent on synchronous bilateral discharges. Interruption of Patients and methods signal transduction via this pathway can therefore potentially inhibit seizure generalization. Further- We retrospectively reviewed our epilepsy surgery more, because of a post-callostomy reduction in database and identified 28 patients who underwent seizures of frontal cingulate origin, it has been CC between January 2003 and April 2005. The mean hypothesized that bilateral frontal lobe involve- age at CC was 9.6 years (range 1.75—20.75 years) ment is necessary for clinical manifestations of some with a mean duration between seizure onset and CC partial seizures.1 Though the corpus callosum is the of 7.3 years. The average number of anti-epileptic preferential pathway for bilateral synchrony, prior drugs (AEDs) tried prior to CC was 8.9 (ranging from experiments have revealed that intense seizure 3 to 15 AED’s). Fifteen patients had complete CC activity may also be spread by corticotegmental (>95% resection) and 13 patients had partial CC, pathways, the thalamus and midbrain. The factors three of whom returned for completion. Post-CC that determine subcortical spread are uncertain, three patients were lost to follow up. Twenty-two but may hold the key to individuals in whom corpus (of 25) patients had a greater than 80% reduction in callostomy is successful.1,2 their targeted seizure type (including three children Corpus callosotomy (CC) was first introduced as a who were seizure-free for greater than 6 months). surgical technique for the treatment for epilepsy in Of the 22 children with seizures after CC, 13 con- 1939.3 It is often used to treat atonic, clonic, myo- tinued to have generalized seizure types, and 9 had clonic, and generalized tonic—clonic seizures.4 The bilateral, independent-onset, partial seizures. We best results have been consistently seen with atonic describe three of these 25 patients (12%) with seizures; however,some success has also been shown intractable epilepsy whose consistent unilateral with tonic and secondarily generalized seizures.5—8 focal features did not become apparent until CC Traditionally, anterior two-thirds or complete was performed and subsequently went on to resec- callosotomies have been the most common proce- tive surgery. Patient demographics are shown in dures. There have been conflicting reports whether Table 1. a complete CC is more beneficial. Studies have All three patients with refractory epilepsy under- ranged from no significant difference between the went a phase one evaluation (including magnetic procedures to a better seizure outcome with com- resonance imaging (MRI), scalp video electroence- plete CC.6—8 The decision to do a partial or complete phalograph (VEEG), magnetoencephalography CC is often dependent on the cognitive and language (MEG), electrocorticography (ECoG) and/or neurop- ability, handedness, and age of the patient.9 sychological testing), which did not definitively pre- In the past, this technique has been reserved for dict the ictal onset zone. All underwent corpus management of medically resistant generalized epi- callosotomy, and then a repeat phase one evaluation lepsies.10 Its role in secondarily generalized seizures, after the callosotomy revealed focal seizure onset particularly in patients with a frontal lobe focus or with localizing ictal and interictal EEG patterns and congenital hemiplegia, has been well-documented focal MEG dipoles. Two patients underwent intra- by Spencer and co-workers.11—17 We hypothesized, as cranial monitoring prior to focal resection and one prior reviews suggested, that after callosotomy it had a functional hemispherectomy. Corpus callosotomy help identify resectable epileptogenic foci 547

Table 1 Patient demographics Patient 1 Patient 2 Patient 3 Sex M M F Age (years) 8 9 9 Age at seizure onset 5 years 2 months 15 months Age at CC (years) 6 7 7 Age at subsequent resection (years) 8 8.5 8 Region of resection Left frontal + MST Functional hemispherectomy Right frontal + MST Additional procedure VNS (after MEG) N/A VNS MEG: magnetoencephalography; MST: multiple subpial transections; VNS: vagus nerve stimulator.

EEG fields and motor dipoles were also assessed when possible. The MEG dipole localization was per- All patients underwent prolonged VEEG recordings formed by an observer (EC, MM) blinded to the phase (XLTEK, Oakville, Canada). The digital EEG was I data. recorded from 20 scalp electrodes placed according Patient 1 is an 8-year-old, left-handed male with to the International 10—20 system. Ictal recordings a normal MRI who suffered a closed head injury at were obtained in all three patients. Most patients age 5 years. The association of his head injury with had extraoperative intracranial video EEG with a seizure onset at 6 years old is, however, unclear. His subdural electrode array that was positioned based parents described him initially developing right on the results of scalp EEG, MRI, and MEG. This VEEG hemibody tonic activity, with frequent episodes of was used both for ictal onset identification and rapid secondary generalization and independent cortical stimulation to identify eloquent cortex. drop attacks. Within 6—8 months he began having Intraoperative ECoG using 4 or 6 channel subdural generalized tonic—clonic (GTC) and atonic seizures, strips were recorded pre- and immediately post- without clinical hints of focality. He often had over operatively. 20 seizures per day. His seizures were intractable to phenobarbital, MRI valproic acid, topiramate, levetiracetam, felbamate, vagus nerve stimulation and the ketogenic MRI studies were performed with a General Electric diet. Intracranial EEG monitoring revealed no clear 1.5 T. Volumetric images were performed utilizing a focus (Table 2). He underwent a complete corpus T1 weighted image (T1WI) sequence. The T1WI callosotomy. His atonic seizures decreased by over sequence generated contiguous 2—5 mm sections 90%, but 3 months after surgery he began having of the entire head using pulse sequence (repetition multiple daily simple and complex partial seizures time/echo time/number of excitations). We also consisting of right hemibody tonic activity, often used axial, coronal and sagittal T2 weighted images, causing falls, and frequent secondary tonic clonic fluid-attenuated inversion recovery images, and seizures. He occasionally had an aura consisting of other images when deemed necessary. These images right upper extremity paresthesia. were completed both pre- and post-surgery. The patient underwent repeat phase one evaluation. The scalp interictal EEG recording revealed Simultaneous MEG/MSI and EEG recording 2.5—3 Hz spike and slow-wave complexes seen predominantly over the left hemisphere and maximal We performed MEG studies using a whole-head 248- over the fronto-central region. The stereotyped channel gradiometer (Magnes 2500WH, 4D Neuroi- ictal events revealed right hemibody tonic activity maging, San Diego, CA). Data sets of spontaneous with versive eye and head deviation towards the MEG and EEG were recorded in a magnetically right, followed often by a post-ictal Todd’s paresis. shielded room (Vacuumschmelze GmbH, Hanau, He occasionally secondarily generalized. The ictal Germany). We used the single moving dipole in a scalp EEG consistently showed left hemispheric spherical head model to localize one equivalent lateralization, but poor localization. Brain MRI current dipole source for each epileptic spike. We showed his prior CC changes but no other abnorm- obtained three fiducial points (right and left pre- alities. Both single photon emission computed tomo- auricular and nasion) for MEG and a thin sliced T1WI graphy (SPECT) and MEG (prior to vagus nerve MRI co-registration. MEG spikes were superimposed stimulator (VNS) placement) were concordant, with over the MRI, creating the magnetic source image ictal SPECT showing left fronto-parietal increased (MSI). Receptive language, somatosensory evoked blood flow and MEG/MSI dipoles located over the 548 D.F. Clarke et al.

Table 2 Epilepsy evaluation before callosotomy Patient 1 Patient 2 Patient 3 Scalp VEEG: Generalized discharges Bilateral independent Generalized discharges interictal (left > right) discharges Independent right and Generalized epileptiform Independent right and left hemispheric or discharges left frontal and temporal fronto-central discharges discharges Synchronous bi-frontal discharges Clinical semiology Aura: none Aura: none Aura: unsure Atonic Infantile spasms treated Atonic with ACTH GTC (rarely preceded by Hemi-tonic Left hemi-body tonic brief tonic stiffening of right upper extremity) Generalized tonic Generalized tonic Æ secondary GTC Myoclonic-astatic Scalp VEEG: ictal Generalized spike/polyspike Generalized voltage attenuation Generalized voltage followed by low frequency fast attenuation followed activity, evolving into spike and by generalized polyspike wave activity better seen over and slow wave discharges the left hemisphere ( contralateral to the neonatal CVA) ACTH: adrenocorticotropic hormone; CVA: cerebrovascular accident; GTC: generalized tonic—clonic; VEEG: video electroencephalography. left frontal—parietal head region with involvement activity was seen maximally over the left frontal/ of the primary motor and sensory area (Fig. 1). MEG/ parietal regions. Extra-operative cortical stimula- MSI somatosensory evoked potentials also defined tion revealed involvement of his primary motor area the primary sensory cortex. There was some overlap in the region of ictal onset. As a result, he under- seen between MEG-defined epileptiform discharges went a left superior frontal topectomy and multiple and somatosensory potentials, suggesting involve- subpial transections over the left primary motor ment of sensorimotor cortices in his seizure genera- area. Pathological tissue from the frontal topectomy tion. revealed subpial gliosis with molecular layer astro- Because of the concordance of the phase one cytosis and ectopic neurons and gliosis in the white data, it was felt that the child might be a candidate matter. Post-operatively he had transient right arm for further resective surgery. However, given the apraxia, which resolved over time. He is presently suspected close proximity of his epileptogenic zone on zonogram and clobazam. He now has occasional to his primary sensorimotor cortex it was felt that he right upper extremity myoclonic jerks, which cause would benefit from intracranial VEEG monitoring him to drop objects, but does not have the drop with subdural electrodes. Ictal onset and interictal attacks or secondarily generalized seizures that he

Figure 1 MEG/MSI of Patient 1 revealing left posterior frontal and centro-parietal dipole clusters. Corpus callosotomy help identify resectable epileptogenic foci 549

Figure 2 MEG/MSI depicting frontal dipoles in Patient 2. Bilateral abnormalities are depicted by the arrows: left arrow, MCA infarct; right arrow, cortical dysplasia. had previously. He is beginning third grade, is more focal (left > right) and generalized epileptiform interactive and is doing much better in school. discharges (Fig. 3A). Ictal scalp EEG showed general- Patient 2 is a 9-year-old, right-handed male with ized onset. a history of transposition of the great arteries His seizures did not respond to treatment with repaired at 1 week of life. This was complicated ACTH, phenobarbital, primidone, oxcarbamaze- by a right middle cerebral artery (MCA) infarction pine, valproic acid, lamotrigine or zonisamide. A with resultant left hemi-paretic cerebral palsy, par- complete corpus callosotomy resulted in cessation tial left hemi-visual field cut, developmental delay, of all seizure types for 2 months. His post-callosot- and neonatal seizures followed by generalized or omy seizure semiology consisted of left upper and left hemi-body infantile flexor spasms treated with lower extremity tonic, then subtle clonic activity adrenocorticotropic hormone (ACTH) with transient with versive eye movement towards the left lasting seizure freedom for approximately 8 months. His 10—30 s with rare secondary generalization. Epilep- seizure semiology consisted of generalized tonic or tiform discharges on his post-CC scalp EEG involved atonic events, without lateralizing clinical features. primarily his right hemisphere (Fig. 3B). MEG/MSI MRI revealed an old MCA infarct affecting the right dipoles were clustered in the right frontal head fronto-centro-parietal area. It also showed a region region (Fig. 2), with rare discharges in the right of ectopic grey matter anterior to the anatomical occipital region. central sulcus of the left hemisphere (both indi- A functional right hemispherectomy was per- cated by arrows in Fig. 2). Initial interictal scalp formed. His post-operative course was complicated EEG at 8 years of age revealed bilateral independent by a bone flap infection requiring removal and

Figure 3 Illustration of the EEG pre- and post-CC in Patient 2: (A) Pre-CC stage II sleep, scalp EEG depicting generalized and synchronous bifrontal discharges with signiﬁcant amplitude asymmetry (left > right) and independent left posterior discharges. He also had frequent independent left > right frontal discharges, not depicted in this illustration. (B) Post-CC stage II sleep, scalp EEG showing a remarkable difference from Pre-CC with frontal epileptiform discharges and runs of parieto-occipital discharges seen on the right, now concordant with the hemisphere in which the neonatal insult occurred. Sleep features are also better deﬁned over the left hemisphere. 550 D.F. Clarke et al.

Figure 4 Illustration of the EEG pre- and post-CC in Patient 3: (A) generalized voltage attenuation followed by low amplitude, fast frequency activity. (B) Voltage attenuation followed by spike/polyspike and slow wave discharges over the right centroparietal region. corrective surgery 2 months later. He recovered Subsequent ictal scalp EEG revealed voltage without sequelae and has remained seizure-free attenuation maximal over the right hemisphere, for 21 months on levetiracetam monotherapy. and with evolution of the seizure polyspike and slow Patient 3 is a 9-year-old, right-handed female wave discharges was often seen over the right cen- with intractable, symptomatic complex partial sei- tro-parietal region (Fig. 4B). Intracranial EEG mon- zures and generalized myoclonic/tonic seizures itoring with subdural grid and strips revealed a large with frequent drop attacks that began at 15 months region of ictal onset involving her right posterior— of age. Her seizure semiology initially consisted of lateral frontal lobe, and the region overlying her left-hemibody tonic events that rapidly evolved to right pre- and post-central gyri. Intra- and extra- intractable generalized seizure types, as described operative cortical stimulation confirmed involve- (Video sequences 1 and 2). Her ictal EEG revealed ment of her eloquent sensory and motor cortices generalized onset (Fig. 4A). Her case was reviewed in the region of ictal onset. She underwent a right by another institution at the age of 5 years. A brain frontal topectomy and multiple subpial transec- MRI done at that time was thought to reveal a lesion tions. She has been seizure-free for the last 25 near the right temporal horn. A right anterior tem- months on valproic acid and leviteracetam. poral lobectomy was done and the pathology revealed gliosis. This MRI, initial workup and pathological tissue were unfortunately unable to be Discussion retrieved for confirmation by our institution. Sur- gery did not lead to seizure control; therefore she The best results from anterior two-thirds and com- was referred by her primary physician to our center. plete CC have been seen in children with atonic, Treatments that were not successful in controlling tonic and, to a lesser extent, generalized tonic— her seizures include phenobarbital, carbamazepine, clonic seizures. Improved seizure control of simple gabapentin, lamotrigine, clonazepam, topiramate, and complex partial seizures is seen less often. zonisamide, felbamate and vagus nerve stimulation. Unless a patient is already significantly cognitively A 90% anterior CC abated her drop attacks and impaired, a partial callosotomy is often done to significantly decreased her generalized events, but minimize neuropsychological side effects and dis- her partial seizures persisted. Following callosot- connection syndromes.6—8 Partial or complete cal- omy she developed daily simple partial seizures. She losotomy was performed in all three children, none would feel as if her left arm was heavy or limp. This of whom had a definitive focus of ictal onset and all was often followed by left body hemi-tonic activity, of whom had rapidly secondarily generalized events with abduction of the upper extremity at the or drop attacks. The procedure significantly shoulder, flexion at the elbow and subtle dystonic decreased or stopped the generalized events, but posturing of her left hand and fingers. Her left lower they all had recurrent focal seizures. Subsequent extremity was less involved, but had brief extension focal resections in two patients and functional with posturing of the foot (Video sequences 3 and 4). hemispherectomy in one patient resulted in good This was sometimes followed by a left-sided Todd’s seizure control. The corpus callosotomies were suc- paresis. cessful in decreasing the generalized seizures and Corpus callosotomy help identify resectable epileptogenic foci 551

Table 3 Epilepsy evaluation after callosotomy Patient 1 Patient 2 Patient 3 Scalp VEEG: Left hemispheric 2—2.5 Hz Bifrontal discharges Generalized and independent interictal spike and wave ED maximal right fronto-centro-parietal in the left anterior region discharges (F4, C4, P4) (Fp1, F3, C3) Right fronto-central discharges (F4, Fz > F3) Occasional spread to the Right parieto-occipital right frontal area (Fp2, F4) discharges MEG/MSI spike Left frontal Right frontal Not able to be performed sources because of prior placement of VNS Pre- and post-central gyri Somatosensory evoked potentials identified the eloquent cortex Clinical Aura: rare right upper Aura: none Aura: left arm dysesthesia semiology extremity paresthesias described as ‘‘heaviness’’ Right hemi-body tonic activity Versive eye deviation and Left hemibody tonic seizures followed by versive head and left hemi-body tonic occasionally followed by left- eye deviation towards the right seizures with occasional sided Todd’s paresis and a persistent right-sided secondarily generalized Todd’s paresis events Verbally responsive during most events Scalp VEEG: Abrupt onset of generalized Generalized voltage voltage attenuation over the ictal spike/polyspike and wave ED attenuation followed by low right hemisphere, and with with maximal amplitude over frequency fast activity that evolution of the seizure the left fronto-central head increased in amplitude and polyspike and slow wave region followed by generalized evolved into monomorphic, discharges were maximal low amplitude fast activity that theta frequency activity over the right centro- increased in amplitude and with intermixed spikes, parietal region increased in frequency prior to maximal over both frontal termination of the seizure head regions Subdural grid Large amplitude spike and slow None Low amplitude fast activity VEEG seizure wave preceding low amplitude, over the region of a 64- fast frequency, gamma/beta channel grid overlying the activity over the anterior and right posterior-lateral frontal superior aspect of a left fronto- lobe, and pre- and parietal 64-channel grid prior post-central gyri to involvement of the entire grid ED: epileptiform discharges; MEG: magnetoencephalography; MSI: magnetic source image; VEEG: video electroencephalography; VNS: vagus nerve stimulator. aided in clarifying the site of onset for the partial intracranial monitoring.19,21—24 This was also seen in seizures (Table 3). two of our patients in whom invasive recordings The interictal MEG discharges localized and later- were done. The additional benefit of MEG as non- alized the epileptogenic region better than scalp invasive functional imaging,23 as done in Patient 1, is EEG, as has recently been reported with other its value in the evaluation and planning of the seizure types.18—21 The electrical fields recorded surgical procedure. by EEG are attenuated by differences in conductiv- With the introduction of vagus nerve stimulation, ity of the brain, cerebrospinal fluid, skull and scalp. the palliative surgery of corpus callosotomy has The magnetic fields recorded by MEG are not come to be viewed as a less favored technique for affected by these structures.18—21 Nakasato et al. treatment of drop attacks. However, we demon- and other groups have found MEG to be a good strate that with proper patient selection, callosot- predictor of the epileptogenic zone identified by omy can be viewed not only as a palliative procedure 552 D.F. Clarke et al. to stop atonic seizures, but also as a diagnostic tool lar accident (CVA) in Patient 2, thus causing early in the determination of surgical candidacy and pos- transference of certain primary functions. Patient 3 sible subsequent focal resection. For those patients also had few post-operative problems, which may whose clinical semiology has some characteristics of have been attributed to her having a partial CC. partial onset epilepsy, transection of the callosal fibers may offer sufficient delay in spread of the ictal activity to allow identification of the primary, Conclusions resectable seizure focus. In patient 2, discharges predominantly seen in the Corpus callosotomy is still useful as a therapeutic less affected hemisphere pre-callosotomy were tool and can have benefits as a diagnostic tool in the clearly absent post-callosotomy, suggesting prior management of some refractory epilepsy. Presently, rapid bilateral synchrony or, though less likely, inde- it is primarily indicated for intractable generalized pendent contralateral discharges pre-callosotomy. or rapidly secondarily generalized seizures and One could argue that a hemispherectomy could have should be still used solely for this purpose. We have been performed as the initial operation in this case. shown that in select patients it may also reveal a The patient, however,had bi-hemispheric pathology, focal region of ictal onset and subsequent resection as shown in Fig. 2. Also, out of concern for the of this focus may improve seizure outcome. complications of hemispherectomy and maintaining In light of this finding, we recommend repeat the neurological function of the affected hemi- evaluation after callosotomy of all patients who sphere, CC has been described as an alternative to are experiencing unilateral partial seizures, to see 13 hemispherectomy. A comparison of the two meth- if they may qualify for further epilepsy surgery. ods found, as expected, significantly less acute and long-term morbidity between the two procedures. Both the neurosurgery and epilepsy literature sup- ports the use of this procedure in patients with Acknowledgment secondarily generalized events as a means of treating the seizures, sometimes resulting in localizing an We thank Ms. Andrea Patters for her editorial assis- ictal focus.11,13,14,16,17,25,26 It was therefore decided tance. to initially perform a CC. This, as predicted by the literature, caused cessation of seizures for 2 months, and when the seizures returned, the scalp EEG and Appendix A. Supplementary data MEG were able to better assist in lateralizing and localizing the region of seizure onset (Fig. 3). Supplementary data associated with this article Apart from the acute surgical complications, can be found, in the online version, at doi:10.1016/ acute and chronic neuropsychological sequelae of j.seizure.2007.04.004. CC may be seen. A disconnection between visual and tactile sensory functions and verbal expression may occur. A patient may recognize an object by sight or touch but cannot name it. This often occurs when a References complete corpus callosotomy is carried out. Speech difficulties with retention of writing skills have been 1. Purves SJ. Selection of patients for corpus callosum section. identified in patients who have right hemisphere In: Spencer SS, Spencer DD, editors. Contemporary issues in language dominance and are right-handed, and the neurological surgery. Cambridge: Blackwell Scientific Pub- lications, Inc.; 1991. p. 69—86. inverse, dysgraphia with retained speech, seen in 2. Roberts DW. Callosal sectioning for the treatment of epilepsy. left hemisphere-dominant speech and left-handed In: Apuzzo MLJ, editor. Neurosurgical aspects of epilepsy. 8,9 individuals. CC did not cause any language or American Association of Neurological Surgeons; 1991 . p. writing deficits in the children described above. A 171—82. disconnection syndrome often seen immediately 3. Van Wagenen WP,Herren RY. Surgical division of commissural pathways in the corpus callosum: related to an epileptic after the procedure is characterized by lethargy attack. Arch Neurol Psychiatry 1940;44:740—59. and an apathetic mutism. This often resolves after 4. Gates JR, Courtney W. Prediction of seizure outcome after the first few days, but may last several weeks. The corpus callosotomy among young children. Epilepsia fact that two of our patients (1 and 2) had brief or no 1993;34(Suppl.):111. associated sequelae directly related to their com- 5. Fuiks KS, Wyler AR, Hermann BP, Somes G. 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