Turkis/i Neurosurgery 10: 71 - 79, 2000 çatnltepe: Pedintr;c EpileJ'sy Siirgery (i)

SpecialPediatric Epilepsy

Considerations andSurgery (I):Presurgical Strategies

Pediatrik Epilepsi Cerrahisi (i): Yas Grubuna Özel Sorunlarve Cerrahi Öncesi Yaklasim Stratejileri

OGUZ ÇATAlTEPE

Institute for Neurology and Neurosurgery, Department of Neurosurgery,Beth Israel University Hospital, New York, NY, U.5.A.

INTRODUCTION

Although, the application of epilepsy surgerytechniques in children have been reported since19605, the surgical management of epilepsy onlyrecently became a mainstream management methodfor children (18,19,21,23,57). In the earlier series,majority of the cases were older children (17,24,38).Gradually, the age of epilepsy surgery cases inchildhood decreased and even series about epilepsysurgery in infants started to be seen in journals in19905. We also witnessed increased number of newpediatric epilepsy surgery programs in most majorchildren's hospitals during the last decade. Thisincreased interest provided us very valuable clinicaland electrophysiological data which helped ourunderstanding of etiopathogenesis of the disease,provided necessary background to define someepileptic syndromes in childhood, to improve ourprotocols for presurgical pa tien tselection, todevelope new surgical techniques and to documentsurgical outcome. As a result, we reached aremarkable stage in epilepsy surgery in infants andyoung children. However, there are still significantcontroversies regarding patient selection criteria,presurgical assessment methods, surgical indications,timing of surgeryas well as appropriate surgicaltechniques (2,18,28,36,38,40,50,51,61).

The infants and young children constitutes avery peculiar group among epilepsy surgery patientsbecause ofsome inherent characteristics. Thechildren with intractable seizures challenge us withunique problems and require special approaches forpresurgical evaluation and surgical strategy.Awareness of age related characteristics, specialparadigms and controversies regarding this patientgroup have utmost importance to provide a goodsurgical outcome. This review aims to defineimportant characteristics of this patient group andreview controversies, present patient selectioncriteria and presurgical strategies. Surgicaltechniques and strategy in pediatric epilepsy caseswill be the subject of second part of this review.

SPECIAL CHARACTERISTICSAND CONSIDERATIONS

Age: Age related issues and characteristicsdominate the discussion about this patient group andneeds to be taken into account to create a reliable

presurgical evaluation protocol. level of cognitivematuration and language development may be asignificant obstacle for our understanding andassessment of subjective manifestations of seizuresduring early. Age mayaiso be a limitating factor forsome presurgical and surgical tests, such as WADA

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test and cortical mapping techniques during surgeryunder local anesthesia. Young children aredeveloping human beings anatomically,physiologically as well as psychosocially. Theyarepsychosocially more fragile than adults because ofmore vulnarable self-image, less developed socialadjustment ability, and a very significan t peer­pressure effect in their daily life. Seizures itself andanti-convulsive medications might easily causepsychosocial developmental problems andsignificantly distruptive behavioral changes in thisage 08,28,30,36,45,50,51).

Harmful Effects on Immature Brain: The effect

of seizures may be much more harmful, at timescatastrophic, on developing brain. Intractablefrequent seizures itself might cause direct adverseeffects on neuronal development. In addition, youngchildren may have very frequent even continuouspostictal states and frequent interictal epileptiformdischarges may cause "nociferous cortex" andpossible secondary epileptogenesis. The number ofclinical and subclinical seizures may be much morefrequent in infants, sometimes up to a hundred in aday. Consequently, intractable seizures may have adeleterious effect on developing brain and may causemental retardation and debilitating behavioralproblems during emotionally formative years ofchildhood. it is not infrequent to observe a"plateauing" or decline in development of infantswith catastrophic seizures. Especially, the patientswith infantil spasms without seizure control arealmost never developmentally normal08,28,30,34,50,61,62,63).

Special Epilepsy Syndromes: In childhood, thetype of intractable seizures are quite atypical andpoorly defined comparing to relatively well definedepileptic syndromes of adults. There are someepileptic syndromes exclusively seen in children andrarely or never occur in adults, such as infantilespasms, Lennox-Gastaut, Rasmussen encephalitisand Sturge-Weber syndrome(18,34,45,50). Theseepileptic syndromes might be catastrophic becauseof associated cognitive and developmental delay orregression and constitute a very significant challengewhich needs to be handled with a great deal ofexpertise. The anatomical distribution of seizurefocuses in children also present special diagnostic andsurgical challenges. Intractable seizures in childrenmore likely arise from extratemporal epileptogeniczones whereas temporallobe epilepsy is seen morefrequently in adults. Because of this characteristic,epileptogenic activity in children may cover

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relatively larger cortical areas and may includeindispensable functional cortical regions. in addition,extratemporal seizures have a tendency of easy andfast propaga tion to a wider cortical areas. Thesecharacteristics make these cases more challenging.Therefore, these patients frequently need invasiveEEG monitoring and stimulation studies withsubdural electrode arrays to localize seizure onsetas well as functionally important areas0,8,9,16,20,21,32,50,51,61 ).

Electroph ysiological Characteris tics:Electrophysiological evaluation of young children's,especially newbom and infants' cortical activity,might be very challenging because of poorly definednormal and abnormal patterns of immature brain andgreat variability of seizure patterns. Even localizingvalue of the EEG findings is a controversial issue inthis age group. Frequently, no interictal epileptiformdischarge is seen in young children and ra rely welldefined epileptiform discharges are seen on EEG.Ictal discharges spread more rapidly in this age andit causes significant difficulty to define epileptogeniczone. Finaiiy, extratemporal origins of seizures,frequent involvement of eloquent cortex andepileptogenic zones covering relatively larger corticalareas in this age group may increase the difficulty todefine the epileptogenic focus. Invasive monitoringand special stimulation paradigms may be frequen tlyneeded in these cases. Therefore, a special expertisein pediatric electrophysiology has utmost importancefor determination and localization of an epileptogenicarea in young children 0,8,32,34,50,51,58,59,63).

Brain Plasticity: Brain plasticity is the ability ofthe immature brain to recover and to reorganizefollowing a cerebral injury including surgical insults.it is a remarkable asset of early childhood. There aresignificant implications about plastic capacity ofyoung brain from experimental animal studies andfrom experiences in humans following surgicalresections or cerebral insults. This data shows that

eloquent brain areas in developing brain, such asmotor and language cortex, can functionallyreorganize after cerebral injury (36,47,55). Althoughthere is not enough data for a reliable guideline,critical age for neuronal plasticity has generally beenaccepted as 6 to 7 years of age. Younger children havea greater potential for functional recovery of neuralintegrity following resective brain surgery or otherinsults. Best known example of this potential isshifting language function following corticalresection or hemispheric brain damage in earlychildhood. Therefore, brain plasticity should be taken

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into account as a significant positive factor fordeciding surgical intervention at early ages(28,31,45,50-,52) .

Medical Intractibility: Another significant issueis medical intractibility criteria in children. In adults,general consensus is to use major antiepileptic drugs(AED) for a certain length of time, which may be afew years, before to decide medical intractibility ofseizures. The criteria to define medical intractibilityin children is significantly different than adults. Firstof all there are limited number of AEDs available for

young children and long-term application of AEDsmay cause significant cognitive and psycosocialeffects on children. Developing brain is much morevulnerable to AEDs side effects, therefore riskibenefit ratio for long-term trials of AEDs is morecritical in children. In addition, presence of certainsyndromes cause intractable seizures by their verynature and does not need a trail period with all AEDs.On the other hand, there is still not enough dataregarding natural history of certain pediatric epilepsysyndromes. Epilepsy in childhood is not a fixedcondition but a process. it may evolve towardintractibility fastly or may stop spontaneouslyincertain types. This characteristics make the issuemore complicated (2,16,18,28,29,50,51,59,61,62).

Timing of Surgery: Obviously, timing of surgeryis an important decision at this age group. Earlysurgical intervention is crucial not just because ofbrain plasticity, but also to eliminate toxic side-effectsof anti-epileptic medications and their negatiyepsychosocial effects. Im~ature brains undergocomplex process of maturation and frequent seizuresitself, frequent postictal status, interictal epileptiformdischarges, effects of antiepileptic drugs as well asunderlying lesion itself may cause serious harm ondeveloping brain during waiting period. it has beendocumented that even if seizures are controlled with

anti-epileptic drugs, interictal discharges may effecton synaptogenesis, may cause cytoarchitecturalchanges and a possible secondary epileptogenic focusin immature brains. This potential constitutes anothersignificant concem in children. it was reported thatSturge-Weber patients with intractable seizures havea better developmental outcome if theyare operatedbefore 1 year of age (41). Some authors believe thatthe earlier the surgical intervention, the less theeventual functional deficiL Therefore, early surgicalintervention has been recommended in these casesto permit attainmen t of the child' s full developmentalpotential without further psychosocial harm and tomaximize developmental potential

çataltepe: Pediatric Epi/epsy Sllrgery (J)

(2,5,18,27,30,38,45,50,59,61) .

Goal of Surgery: Surgical management ofepilepsy in well selected cases may help children fora normal transition into adulthood by preventingsome psychosocial problems induding dependeney,poor self-esteem, learning disability and by avoidingsignificant side-effects of long-term exposure to anti­convulsive medications. As a result, the purpose ofsurgery is als o somewhat different in this age groupthan adults. The goal of the surgery is not onlycontrolling seizures but also preventing the possibleharmful consequences of uncontrolled seizures and"nociferous" cortex, secondary epileptogenesis,psychosocial problems secondary to cognitive andbehavioral effects of epilepsy, and avoiding side­effects of antiepileptic medications by succeedingdiscontinuation or significant decrease ofmedications (2,16,18,20,28,29,30,36,45,50,51,61-63).

SPECIAL EPILEPSY SYNDROMESOF CHILDHOOD

Some epileptic syndromes are exdusively ormostly seen in children and frequently present adiagnostic and surgical challenge. A brief overviewof these syndromes will help to define uniquecharacteristics and problems of this patient group.

Sturge-Weber Syndrome: There are a greatvariability in the severity of epilepsy in patients withSturge-Weber syndrome (SWS), however seizuresusually start within the first year of life. The childrenwith SWS are characterized by facial and ipsilateralcerebral angiomatosis. Some patients have medicallyintractable epilepsy with very frequent seizures andprogressive neurological deficits, whereas some otherpatient's seizure remit and neurological deficits donot progress. These patients may develop progressivehemiparesis, hemianopsia and become mentallyretarded after the onset of uncontrollable seizures.

On the other hand, accumulating data shows thatearly surgery, especially surgery before 1year of age,leads to the best outcome by ensuring maximalrecovery and avoiding further cognitive dedine. Thi~unpredictable course of disease and benefit of earlysurgical intervention makes management plan verychallenging and controversia1. Therefore, it has beenrecommended that each case should be assessedindividually. Surgery should be considered if thepatient had uncontrollable seizures despite ofadequate medical management and had progressivecognitive deterioration and progressive hemiparesis.Depending on the size of involved cortical area, a

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limited cortical resection or hemispherectomy rnightbe procedure of choice. Diffuse hemisphericinvolvement accompanied by a progressive deephemiparesis leads patient to hemispherectomy. Theresult of surgery is excellent for seizure con trol(5,22,26,27,28,41,45,51).

Rasmussen' s Encephalopathy: Although, it wasdescribed as encephalitis initially, the causativefactors of Rasmussen's encephalopathy are stilIunknown. A typical patient presents with infrequentpartial seizures between 4 and 9 years of age. Theseizure frequency increases along graduallyincreasing hemispheric involvement and the patientmay develop epilepsia partialis continua, progressivehemiplegia and mental retardation. Although corticalbiopsy may be obtained to confirm the diagnosis incontroversial cases, focal resections neither stop theprogression of the disease nor significantly decreasethe number of seizures. Eventually, chronicinflammation spreads to the entire ipsilateralhemisphere. Procedure of choice is hemispherectomywhen the patient has severe herniparesis with absentfine finger movements (4,28,45,48,51,62,63).

Infantile Hemiplegic Epilepsy; This is not a weii­defined entity. Same authors prefer to use "infantilehemiplegic epilepsy" term for a group of congenitaldisorders charaderized with intractable partialseizur.es and hemiparesis secondary to hemisphericinsults. The underlying lesion in this group ofpatients might be cortical dysplasia,hemimegalencephaly, congenital porencephaly, orperinatal cerebrovascular events. The patientsusuaiiy present with severe and intractable seizureswithin the first few months of life, and hemiparesisbecomes prominent between the ages of 3 and 6months. The procedure of choice is hemispherectomy(45,48,50,51,54,56,57,62,63).

Infantile Spasms: Infantile spasrns is a diseaseof infancy period. A typical patient presents withmyodonic seizures which starts between 4 and 8months of age and characteristic hypsarrhythmicEEG pattern. The patient frequently proceedsprofound mental retardation. Seizures are oftenresistant to medical management, although ACTHmight help in some cases. Underiying focal lesionmay be cortical dysplasia, ischemic injury orelectrophysiological findings provide very limitedhelp to identify the site of seizure onset at this age.Therefore, functional imaging studies to d'efinestructuraiiy abnormal area have utmost importancefor surgical planning. These patients are very difficult

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cases unfortunately. However, resection ofstructuraiiy abnormal area may provide some benefitin properly selected patients 04,28,34,45,61-63).

Lennox-Gastaux Syndrome: The patientspresent with frequent, intractable seizures (tonic,atonic, myodonic), mental retardation and typicalslow spike and wave pattem at EEG. it has beengenerally accepted as generalized seizure disorderand surgical options are limited to corpuscallosotomy and vagal nerve stimulation. However,there are some documen ted cases wi th focal

radiological abnormalities and these cases respondfocal resection weii 08,45,51,61-63).

Laundau-Kleffner Syndrome: Landau-Kleffnersyndrome is characterized with partial andsecondarily generalized seizures and languageregression. The natural course of the disease isvariable. The seizures cease spontaneously in manycases. In case of intractable seizures, the children maybenefit from multiple subpial transection technique(39).

Neuronal Migrational Disorders: Although it isnot an exdusively childhood syndrome, neuronalmigrational disorders constitutes a large group ofcongenital structurallesions which frequently causeintractable epilepsy. NMDs result from disruptionof normal process of neuronal cell migration andcharacterized by disorganization of corticalarchitecture and ectopic location of neurons. Theyrepresent broad variety developmental abnormalitiesinduding agyria/pachygyria Oissencephaly), focalcortical dysplasia, polymicrogyria, schizencephaly,unilateral megalencephaly, gray matter heterotopiasand microdysgenesis. Focal resection is thetreatment of choice in the management of epilepsysecondary to focal neuronal migrational disorders.Focal NMD are often accompanied by anepileptogenic area which often more widespreadthan seen in MR!. Therefore, determining the extentof structurallesion and epileptogenic zone involvesan enormous challenge during presurgicalevaIuation. Invasive monitoring with subdural platesand intraoperative ECoG are best tools to determinethe extent of epileptogenic areas. Identification andcomplete resection of lesion and ictal onset zone isan exceiient predictor of good outcome along theconcordance of structural, functional andelectrographical abnormalities. if the resection of thelesion is not possible be cause of eloquent cortex,multiple subpial transection may be an option0,3,6,7,10,44,49).

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Temporal Lobe Epilepsy in Children: Temporallobe epilepsy constitutes a smaIler percentage ofsurgical cases in childhood comparing to adultepilepsy patients (46,51). A typical temporal lobeepilepsy patient presents with simplel complexpartial seizure wi thl wi thou t secondarily generalizedtonic-clonic con vulsions. Electrophysiologica IIy,epileptiform discharges are often localized in mesialtemporallobe, although neocortical involvement isnot rare. Although children older than 6 or 7 yearsoften have similar clinical features to those seen in

adulthood, clinical features of complex partialseizures in infants and young children may be verysubtle or atypicaL. Routine interietal EEC might benormal at this age. EEC-Video monitoring has verycritica i importance for definitive diagnosis.Underlying lesion is rarely mesial temporal sclerosisin this age contrary to adult patients, but often slowgrowing tumors, developmental abnormalities suchas cortical dysplasia, infaretion secondary to perina talischemic events and previous infections. Anotherimportant difference in children with temporallobeepilepsy is chance of having spontaneous remissionup to 10 to 18%. However, seizures originating fromtemporallobe with developmental abnormalities ininfants and young children are aiready intractableby its inherent caharaeteristics.

SELECTION OF SURGICAL CANDIDATES

Main principles applied to surgical candidatesin adult epilepsy patients are also relevant tochildren: presence of medically intraetable seizurespreventing normal daily activity andi or interferingwith normal quality of life, preferably localizedepileptogenic zone and strongly favorable riskibenefit ratio with low risk of post-operative newneurological deficiL However, children present anumber of unique challenges as mentioned above.Many childhood seizure disorders may remitspontaneously. Buteven if spontaneous remission ofseizures occurs, long term effects of seizures, frequentpostictal states, frequent interictal discharges andside-effects of anti-epileptic drugs may still causesignificant psychosocial and neurologicalimpairment, neuro-developmental problems orarrest of maturation during this period. Brainplasticity and recovery Ireorganization potential ofthe brain is a time-limited major advantage. Underthe light of these characteristics, children withintractable epilepsy should be seleeted carefully forsurgical evaluation based on an individualizedassessment criteria (18,20,21,28,36,45,50,51,59,61-63).

çataitepe: Periiatric Epileps!! Siirger!! (i)

The primary goal of the presurgical evaIuationis determining whether or not there is any focal originof seizures. if there is a focal epileptogenic area, thenthe goal is determining whether or not that focus canbe removed without ca us ing any unacceptableneurological deficiL if there is no epileptogenic focusor reseetive surgery would cause serious neurologicaldeficits, then the goal of presurgical evaluation is todetermine if there is any other surgical techniquewhich may help the patient such as corpuscallosotomy, multiple subpial transection or vagalstimulation. After selecting the patients as a surgicalcandidate, the presurgical evaluation starts withrelatively simple and non-invasive procedures, butmay progress to quite complex and invasiveprocedures. Critica i information is obtainedprimarily by recording habitual seizures during EEC­Video monitoring to characterize their clinicalmanifestations and to correlate the clinical findingswith the electroencephalographic abnormalities. Thedata provided by history, neurological examination,neuropsychologic evaluation, and both anatomic andfunctional neuroimaging studies also provide veryvaluable supporting information. Therefore at thispoint" it will be helpful to review briefly majordiagnostic tests used for pre-surgical evaluation.

PRESURGICAL EVALUA TION

Neuropsychological Tests: Pre-operativeneuropsychological tests to assess verbal and non­verbal communication skills and the level of

psychosocial adjustment are well-established toolsin adults. it mayaiso provide adjunctive informationabout the localization or at least the lateralization ofthe epileptogenic region. it is also significantdiagnostic test for children. However,neuropsychological assessment of young children isdifficult because of limited cognitive skills andcooperation (28,45).

Neuroimaging Studies:

MRI: MRI with special parameters is a veryvaluable tool for detecting any structural abnormalityand for surgical planning in epilepsy patients. TheevaIuation of MRI in pediatric cases withdevelopmental abnormalities might be difficultbecause of subtleties in some cases such as dysplasticgyral abnormalities and should be reviewed by aradiologist experienced in epilepsy. MRI volumetricstudies and MR spectroscopy are valuable tools inadults but the experience with children is stilllackingin these areas and theyare not a routine part of

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presurgical study at this point. Although, MRIvolumetric studies probably have not much criticalimportance in children, MRS may have a potentialof providing some important information in future.On the other hand, functional MRI has already beenan imaging study which provides invaluable data inepilepsy patients. Functional MRI maps functionalbrain activation indirectly by detecting focal changesin cerebral hemodynamics and metabolismsecondary to a specific function related neuronalactivity. The location of the epileptogenic zone withrespect to eloquent cortex, including sensorimotor,language, memory, and visual areas has a criticalimportance in resective surgery. Several factors suchas individual variability, anatomic distortion bycorticallesions, or cortical reorganization can makefunctionallocalization based on classical anatomical

landmarks imprecise and unreliable during surgery.Therefore, fMRI constitutes a powerful non-invasivemethod to map functional cortical areas in relationto epileptogenic zone and increases the precision,accuracy, and safety of neurosurgical procedures.However, fMRI has a limited value in young childrenbecause it requires a significant amount ofcooperation from patients throughout the study(18,28,33,45,51).

SPECT AND PET: Functional neuroimagingtechniques have an important place in identificationof surgical cases in epilepsy. Cerebral blood flowincrease during seizure at epileptogenic focus andthis hyperperfused area can be detected by icta1.Single photon emission tomography (SPECT), whilehypoperfusion is seen on the interictal SPECT. IctalSPECT is especiaIly helpful for localizing seizurefocus in children given the high proportion ofchildren with extratemporal seizures whom presentwith normal or nonspecific MRI seans. Like SPECT,positron emission tomography (PET) is anothernoninvasive, functional imaging study which mayprovide significant data to localize epileptogeniczone and cortical abnormality. Interictal PET seanreliably demonstrates a region of hypometabolismcorresponding with the zone of cortical abnormalityand correlates well with eleetrocorticographicalfindings. PET sean detects metabolic changesassociated with cytoarchitectural disturbances anddysgenesis in children in whom MRI reveals little orno structural lesions. Although data is much lesslimited for children with epilepsy cornparing toadults, PET and SPECT have been shown as veryvaluable tools in the patient selection process inchildren (12,13,14,25,28,51).

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Electrophysiological Techniques:

Electroencephalography and EEC-VideoTelemetry: Electroencephalography is most criticaltest for localizing epileptogenic focus and planningsurgery. Although, routine EEC may documentinterictal electroencephalographic abnormalities, itis a very limited study to localize epileptogenic focus.Determining the onset of electroencephalographicseizures is considered the most reliable localizingsign and it is almost only possible with long-termcontinuos EEC monitoring techniques. Therefore,EEC-Video Telemetry is cornerstone of presurgicalassessment. EEC-Video monitoring gives us veryvaluable data during presurgical evaluationincluding clinical and electroencephalogra phiccharacteristics and consistency of seizures, the siteof electroencephalographic seizure onset and itsclinical correlates (28,46,51,59-61).

Invasive Electrophysiological Monitoring: Notinfrequently, the site of seizure onset can not belocalized using surface eleetrodes or clinicalsemiology, neuroimaging and neuropsychologic datamay not concordant with the EEC findings. Invasiveelectrophysiological monitoring techniques includingsubdural, epidural or depth electrodes may need tobe used in these cases. More specificaIly; (1) partialseizures in the setting of normal or non-Iocalizingimaging data, (2) epileptogenic zone that are morewidespread than the structural lesion, (3) absolutenon-congruence data, (4) multiple lesions andi ormultifocal interictal epileptiform activities and (5)superimposed epileptogenic areas and eloquen tcortex constitute main indications for invasive

electrophysiological monitoring. Invasive monitoriiigtechniques have a key importance in children. Deptheleetrodes are rarely used in children in contrast tosubdural electrodes. Subdural electrodes are used

frequently because of higher incidence ofextratemporal epilepsy in this age group. Althoughsubdural eleetrodes provide more detailed andprecisely localized information, it has a disadvantageof being less helpful in exploring more widespreadlocalization problems over large cortical areasbecause of limited sampling potential(1,11,15,18,28,32,35,51,59).

Cortical Mapping: Eloquent cortex showsignificant variability by being in different locationsin different patients and by being in consideredsurgically safe areas based on gross anatomic criteria.In addition, essentiallanguage areas can be spreadto multiple smaIl areas in some patients and intrinsic

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lesions in brain may cause displacement offunctionally important areas from their usualanatomic location. This substantial individual

variability of functionaiiy critical areas underscoresthe importance of individualized mapping.However, it should be reminded that whether or not

a certain cortical region is critical for a particular taskmay be difficult to determine and generaiiy dependson the mapping techniques used. All mappingtechniques provide approximations, thereforeseveral cortical mapping techniques should be usedto improve resolution of map in difficult cases.Cortical EEG and mapping can be performed in theoperating room after craniotomy with the patientunder local anesthesia or extraoperatively afterimplantation of subdural grids. Although, childrenas young as 8 years old may tolerate and cooperateintraoperative cortical stimulation for functionalmapping procedures, this may be very difficult withsome children, especially very young children.Extraoperative mapping techniques with implantedsubdural electrodes should be preferred in thesechildren. Extraoperative electrical corticalstimulation with subdural grids is particularlyhelpful to map eloquent cortex for planning a safeand effective resection in children with an

epileptogenic zone adjacent to functionaiiy critica 1

areas. However, extraoperative cortical stimulationmay stiii be difficult in young children because oflimited language abilities, short attention span and.cooperation problems. In addition, children underage 2 or 3 years may not show motor responses withcortical stimulation techniques (11,42,43,53).

Intraarterial Amobarbital Test: Amobarbital test

(IAT) is used to lateralize dominant side for languageand memory function to prevent possiblepostsurgicallanguage and memory deficits in somecases. Although IAT is reliable to determine languagedominance, it is not so reliable in determination of

memory dominance in children. lts application inchildren is limited with more complex situation, suchas the identification of the origin of seizure onset inthe middle or posterior portion of the temporallobein the language-dominant hemisphere. The plasticityof the young brain and its ability to switch languagedominance in young children also make this test lesspertinent for young children (18,45).

CONCLUSION

Overali, epilepsy surgery in children constitutesa significant advancement in the management ofmedicaiiy intractable epilepsy of a highly vulnerable

Çataltepe: Pediatric Epi/epsy Surgery (i)

group of patients. However, available data does notprovide weii-defined guidelines and parameters forpresurgical assessment and decision making processin this patient group. The children are developinghuman beings and epilepsy in children is not a fixbut an evolving and complicated process. Therefore,selecting and referring young patients to surgery isa delicate process which needs to be handled by anexperienced team. it is very important to find adelicate balance between avoiding an unnecessarysurgery and causing psychosocial deterioration asweii as experiencing si de effects of antiepilepticmedications based on unrealistic expectations ofspontaneous remission. Present data showssatisfactory evidence that epilepsy surgery inchildhood is a safe and effectiye therapy with weiiselected cases and adequate surgical technique.Earlier surgery and earlier seizure control contributesto a greater reduction in overall morbidity andimproves quality of life in children. Children withretractable epilepsy should be identified withoutdelay and evaluated.

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