seizures are the most common neurological events of childhood with approximately 35% of children experiencing a seizure at some point in their lives 25% of whom subsequently go on to develop epilepsy . the prevalence of epilepsy in india is 4.9 to 6.2 per 1000 population . of these patients with epilepsy , 43% comprises of children and adolescents .  intractable epilepsy  is defined as a failure to respond to at least two antiepileptic drugs ( aeds ) given over at least a two - year period . a single definition for  intractable epilepsy can not suit all situations as definitions of intractability are individualized to the patient . of these patients deemed to be intractable , approximately 50% are estimated to have surgically remediable epilepsy [ 4 , 5 ] . hemispheric epilepsy  ( he ) refers to epileptiform activity in all four lobes of one hemisphere , and when it involves more than two lobes of the brain , it is termed  subhemispheric epilepsy  ( she ) [ 4 , 6 , 7 ] . these hemispheric brain lesions are commonly associated with early onset of catastrophic epilepsies and multiple seizure types that inhibit brain development . these respond well to early hemispheric / subhemispheric disconnective / resective surgeries [ 69 ] . an analysis was done of the pre- and postsurgical data of 34 children who underwent disconnective epilepsy surgeries , that is , a peri - insular hemispherotomy ( pih ) or a peri - insular posterior quadrantectomy ( pipq ) for hemispheric / subhemispheric epilepsy from april 2000 to march 2011 . the hemisphere contralateral to the hemiparesis was shown by radiological ( mri / computerised tomography ( ct ) ) and functional ( scalp eeg / eeg video telemetry ) imaging to have a unilateral diffuse abnormality and the remaining hemisphere was normal . when the epileptogenic zone encompassed large areas of the temporal , parietal and occipital lobes with sparing of the frontal lobe the decision was dependant on good concordance between the imaging ( mri , ct , nuclear studies ) , eeg , clinical and neuropsychological evaluations , and a clear localization of the lesion to the unilateral - affected region . the indications for pipq were the same as for hemispheric epilepsy , the pathology being localized to involve the temporal , parietal , and occipital lobes . the presence of residual voluntary motor function of the contralateral distal musculature , that is , finger opposition and foot tapping , was the indication for pipq preserving eloquent uninvolved sensorimotor cortex . all patients went through a presurgical evaluation including a study of the seizure semiology , neurological examination , multiple electroencephalogram ( eeg ) examinations ( video telemetry ) , magnetic resonance imaging ( mri ) , and neuropsychological evaluation . the focus of the evaluation was to identify a surgically remediable epilepsy syndrome with good electro - clinico - radiological concordance . if the structural lesion responsible for epilepsy could be safely removed without causing deterioration in the functional status , the patient was considered for epilepsy surgery . however , if there was no concordance in investigations in the phase i evaluation , the patient would enter a phase ii evaluation which would include prolonged invasive eeg monitoring , nuclear medicine studies ( positron emission tomography ( pet ) and single photon emission computerized tomography ( spect ) ) , and a wada ( sodium amylobarbital ) test . however , none of our patients required a phase ii evaluation . ( figure 1 ) this is a surgical method of functional hemispherectomy that enables disconnection of the hemisphere through peri - insular windows requiring limited removal of the fronto - parieto - temporal opercular cortices . following the surgical principles of  anatomical subtotal removal of the hemisphere and complete disconnection , the pih is a radical hemispheric tractotomy based on the concept of maximum disconnection with minimal excision . it resulted from the demonstration that the hemisphere could be disconnected , made nonfunctional , through very small removal of brain tissue [ 9 , 14 , 15 ] . a pipq was performed in all cases of subhemispheric epilepsy and the surgery tailored to encompass the whole epileptogenic lesion yet preserving the central region , which is still functional . ( figure 2 ) in this technical variant , there is a minimal removal of brain tissue but complete disconnection of the remaining major part of the abnormal cortex , which is left anatomically intact and viable by preservation of the arteries and veins irrigating these lobes . the primary motor and sensory cortices are identified and recognized from the study of the mri and correlation with intraoperative surface anatomy , based on gyral pattern , arteries , and veins [ 6 , 7 ] . the identification of the functional cortex is also aided by electrophysiological means under general anaesthesia before the disconnection . this identification maximizes both the extent of resection and the safety of surgery [ 6 , 7 ] . in this variant , the mesial temporal structures are resected , but the temporal neocortex is disconnected and not resected followed by a parieto - occipital disconnection [ 6 , 7 ] . the data was analyzed with nonparametric tests because of the small sample size among the children with poor outcome following surgery ( engel 's class ii nonparametric  square test and mann - whitney u test was were to compare the categorical and continuous variables between the groups . p < 0.05 ( two tailed ) was considered significant and data was analyzed using spss ( version 19 ) . the mean age of seizure onset was 3.8 years ( range : from neonates to 12 years ) . the mean duration of epilepsy was 4 years ( range : from 3 months to 14 years ) . 28 children ( 82.3% ) had a seizure frequency of 2 episodes / day , while 11 ( 32.3% ) had at least one episode of status epilepticus prior to surgery . epilepsy was due to rasmussen 's encephalitis ( re ; n = 11 ) ( figure 3 ) , infantile hemiplegia seizure syndrome ( ihss ; n = 12 ) ( figure 4 ) , hemimegalencephaly ( hm ; n = 3 ) ( figure 5 ) , sturge weber syndrome ( sws ; n = 4 ) ( figure 6 ) , and postencephalitic sequelae ( pes ; n twenty - seven ( 79.4% ) patients underwent pih for lesions causing hemispheric epilepsy , and seven ( 20.6% ) underwent pipq for lesions causing subhemispheric epilepsy . the seizure outcome after surgery was assessed by engel 's classification   and is described along with followup in table 1 . we recorded 11 variables and analyzed them to arrive at predictive variables of a complete seizure freedom . we found that age of seizure onset ( p = 0.03 ) and the etiology of the disease causing epilepsy ( p = 0.007 ) were predictive variables for the same . patients who had re , sws , pes , and ihss had good seizure outcomes following surgery . the results of our cognitive outcomes that have been published before   show that the mental and social age showed a steady increase after surgery . however , in the long term , intelligence quotient ( iq ) showed only a gradual gain on followup . older age of onset of seizures and a shorter duration of seizures prior to surgery were predictive of positive cognitive gains following surgery . complications in this series included pseudomeningocele in 2 ( 5.8% ) and low pressure hydrocephalus in 1 ( 2.9% ) who required a low pressure ventriculoperitoneal shunt . this is quite low as compared to other published series ( table 4 ) [ 911 ] . we also had 15 patients who developed postoperative fever , but csf cultures were sterile . this could have been due to an aseptic meningitis due to the presence of blood products in the disconnected cavity . our series documents 91.1% seizure freedom , which is similar to other published studies [ 9 , 12 , 1621 ] . following functional hemispherectomy , seizure free outcomes have ranged from 52 to 90% [ 9 , 1621 ] . this range could be explained by differences in patient selection or technical pitfalls such as incomplete removal in anatomical hemispherectomy and incomplete disconnection in functional hemispherotomy [ 14 , 19 ] . we found the age of seizure onset to be a strong predictor of seizure freedom ( table 2 ) . this finding is also supported by other studies [ 3 , 22 , 23 ] . a younger age of seizure onset is usually seen in children with developmental cortical malformations and multifocal epilepsy , which are proven to have poor seizure control . the etiology of the disease producing epilepsy is also a strong predictor of seizure freedom ( table 3 ) . the best results in our series were obtained in children suffering from re , sws , pes , and ihss ( table 3 ) . ihss and sws are seen in the perinatal age group , and they are generally unilateral with complete sparing of the opposite side . there has been evidence to support that in such cases , early surgical intervention facilitates good seizure control and helps the uninvolved hemisphere to develop and take over the functions of both sides . however , in one patient with ihss , we had a class ii seizure outcome and this was in the initial part of the series , which could be attributed to incomplete disconnection , and this patient was lost to follow up . all patients with re had a class i seizure outcome as this disease also strictly affects only one hemisphere . however , the seizure outcome in patients with hm was not satisfactory as described in literature , and this has been reported in other series too [ 9 , 1721 ] . the likely explanation could be the presence of migrational abnormalities in the so - called  preserved hemisphere  or early development of an epileptic encephalopathy , already in utero . we found a significant gain in the mental and social age in the immediate postsurgical period which continued into the second and third years of followup . our study   also showed that older age of onset of seizures showed positive mental and social age gains at followup . onset of intractable epilepsy within the first 24 months of life is a significant risk factor for mental retardation , especially if seizures occur daily [ 12 , 24 ] . most of these children have a low dq / iq to begin with and the improvement in cognitive skills after surgery is poorer in these children . furthermore , our study   also showed that a shorter duration of seizures prior to surgery is predictive of positive mental and social age gains , a finding that is in keeping with those of freitag and tuxhorn   and basheer et al . . in general , children with ie in our country are not exposed adequately to environmental stimuli as schooling is discontinued in the presence of seizures . with good postoperative seizure control , the child 's attention capacities increase and they engage in social interaction with their family and peers . an improved school attendance due to seizure freedom improves their adaptive skills that in turn helps the child improve his performance in activities of daily living . in our experience , over 90% of children with hemispheric and subhemispheric epilepsy syndromes achieve an excellent seizure outcome with less morbidity following epilepsy surgery . age of seizure onset and etiology of the disease causing epilepsy are independent predictive variables of a good seizure outcome . following seizure freedom , improvement of function in the residual brain occurs that in turn leads to improvement in adaptive and social functions and quality of life .
objectives : to study the outcome of disconnective epilepsy surgery for intractable hemispheric and sub - hemispheric pediatric epilepsy . 
 methods : a retrospective analysis of the epilepsy surgery database was done in all children ( age < 18 years ) who underwent a peri - insular hemispherotomy ( pih ) or a peri - insular posterior quadrantectomy ( pipq ) from april 2000 to march 2011 . 
 all patients underwent a detailed pre surgical evaluation . 
 seizure outcome was assessed by the engel 's classification and cognitive skills by appropriate measures of intelligence that were repeated annually . 
 results : there were 34 patients in all . 
 epilepsy was due to rasmussen 's encephalitis ( re ) , infantile hemiplegia seizure syndrome ( ihss ) , hemimegalencephaly ( hm ) , sturge weber syndrome ( sws ) and due to post encephalitic sequelae ( pes ) . 
 twenty seven ( 79.4% ) patients underwent pih and seven ( 20.6% ) underwent pipq . 
 the mean follow up was 30.5 months . at the last follow up , 31 ( 91.1% ) were seizure free . 
 the age of seizure onset and etiology of the disease causing epilepsy were predictors of a class i seizure outcome . 
 conclusions : there is an excellent seizure outcome following disconnective epilepsy surgery for intractable hemispheric and subhemispheric pediatric epilepsy . an older age of seizure onset , re , 
 sws and pes were good predictors of a class i seizure outcome .