Vertical parasagittal hemispherotomy: surgical procedures and clinical long-term outcomes in a population of 83 children

Hemispherectomy in the treatment of seizures: a review

The term hemispherectomy refers to the complete removal or functional disconnection of a cerebral hemisphere. The technique was initially developed over 85 years ago to treat infiltrating brain tumors but is now used exclusively for medically refractory epilepsy. Hemispherectomy surgery has progressed from an extremely morbid procedure fraught with complications to a fairly routine one performed at most pediatric epilepsy centers with relatively low risk and great efficacy. The author reviews the history and evolution of hemispherectomy surgery, the relevant pathological conditions, as well as outcomes and complications.

Long-term outcomes of hemispheric disconnection in pediatric patients with intractable epilepsy

Background and Purpose

Hemispherectomy reportedly produces remarkable results in terms of seizure outcome and quality of life for medically intractable hemispheric epilepsy in children. We reviewed the neuroradiologic findings, pathologic findings, epilepsy characteristics, and clinical long-term outcomes in pediatric patients following a hemispheric disconnection.

Methods

We retrospectively studied 12 children (8 males) who underwent a hemispherectomy at Asan Medical Center between 1997 and 2005. Clinical, EEG, neuroradiological, and surgical data were collected. Long-term outcomes for seizure, motor functions, and cognitive functions were evaluated at a mean follow-up of 12.7 years (range, 7.6-16.2 years) after surgery.

Results

The mean age at epilepsy onset was 3.0 years (range, 0-7.6 years). The following epilepsy syndromes were identified in our cohort: focal symptomatic epilepsy (n=8), West syndrome (n=3), and Rasmussen's syndrome (n=1). Postoperative histopathology of our study patients revealed malformation of cortical development (n=7), encephalomalacia as a sequela of infarction or trauma (n=3), Sturge-Weber syndrome (n=1), and Rasmussen's encephalitis (n=1). The mean age at surgery was 6.5 years (range, 0.8-12.3 years). Anatomical or functional hemispherectomy was performed in 8 patients, and hemispherotomy was performed in 4 patients. Eight of our 12 children (66.7%) were seizure-free, but 3 patients with perioperative complications showed persistent seizure. Although all patients had preoperative hemiparesis and developmental delay, none had additional motor or cognitive deficits after surgery, and most achieved independent walking and improvement in daily activities.

Conclusions

The long-term clinical outcomes of hemispherectomy in children with intractable hemispheric epilepsy are good when careful patient selection and skilled surgical approaches are applied.

Surgery for childhood epilepsy

Approximately 60% of all patients with epilepsy suffer from focal epilepsy syndromes. In about 15% of these patients, the seizures are not adequately controlled with antiepileptic drugs; such patients are potential candidates for surgical treatment and the major proportion is in the pediatric group (18 years old or less). Epilepsy surgery in children who have been carefully chosen can result in either seizure freedom or a marked (>90%) reduction in seizures in approximately two-thirds of children with intractable seizures. Advances in structural and functional neuroimaging, neurosurgery, and neuroanaesthesia have improved the outcomes of surgery for children with intractable epilepsy. Early surgery improves the quality of life and cognitive and developmental outcome and allows the child to lead a normal life. Surgically remediable epilepsies should be identified early and include temporal lobe epilepsy with hippocampal sclerosis, lesional temporal and extratemporal epilepsy, hemispherical epilepsy, and gelastic epilepsy with hypothalamic hamartoma. These syndromes have both acquired and congenital etiologies and can be treated by resective or disconnective surgery. Palliative procedures are performed in children with diffuse and multifocal epilepsies who are not candidates for resective surgery. The palliative procedures include corpus callosotomy and vagal nerve stimulation while deep brain stimulation in epilepsy is still under evaluation. For children with "surgically remediable epilepsy," surgery should be offered as a procedure of choice rather than as a treatment of last resort.

Long-term outcome of surgical disconnection of the epileptic zone as an alternative to resection for nonlesional mesial temporal epilepsy

BACKGROUND

Pharmacoresistant epilepsy can be treated by either resection of the epileptic focus or functional isolation of the epileptic focus through complete disconnection of the pathways of propagation of the epileptic activity.

OBJECTIVE

To evaluate long-term seizure outcome and complications of temporal lobe disconnection (TLD) without resection for mesial temporal lobe epilepsy (MTLE).

METHODS

Data of 45 patients operated on for intractable MTLE using a functional disconnection procedure have been studied. Indication of TLD surgery was retained after a standard preoperative evaluation of refractory epilepsy and using the same criteria as for standard temporal resection.

RESULTS

Mean follow-up duration was 3.7 years. At the last follow-up, 30 patients (67%) were completely seizure-free (Engel-Ia/International League Against Epilepsy class 1) and 39 patients (87%) remained significantly improved (Engel-I or -II) by surgery. Actuarial outcome displays a 77.7% probability of being seizure-free and an 85.4% probability of being significantly improved at 5 years. No patient died after surgery and no subdural haematoma or hygroma occurred. Permanent morbidity included hemiparesis, hemianopia and oculomotor paresis found in three, five and one patient, respectively, after TLD.

CONCLUSIONS

TLD is acceptable alternative surgical technique for patients with intractable MTLE. The results of TLD are in the range of morbidity and long-term seizure outcome rates after standard surgical resection. We observed a slightly higher rate of complications after TLD in comparison with usual rates of morbidity of resection procedures. TLD may be used as an alternative to resection and could reduce operating time and the risks of subdural collections.

Epilepsy surgery in children with accompanying impairments

The aim of this study was to assess seizure outcome 2 years after epilepsy surgery in a consecutive series of paediatric patients, with special focus on children with learning disabilities and other neuroimpairments in addition to the epilepsy. Outcome 2 years after surgery was assessed in 110 of 125 children operated upon for drug resistant epilepsy in Gothenburg 1987-2006. More than half of the children had learning disabilities, 43% motor impairments and 30% a neuropsychiatric diagnosis. Fifty-six per cent of those with an IQ < 70 became seizure-free or had a >75% reduction in seizure frequency, and two thirds if the operation was a resection. The corresponding figure in those with more than 100 seizures per month was 15 out of 31, and another seven had a 50-75% reduction in seizure frequency. The message is that learning disability, motor impairment and psychiatric morbidity should not be contraindications for paediatric epilepsy surgery. More than half of the children with learning disabilities had a worthwhile seizure outcome, with even better results after resective surgery. Children with drug resistant epilepsy and additional severe neurological impairments should have the benefit of referral to a tertiary centre for evaluation for epilepsy surgery.

Which is the most appropriate disconnection surgery for refractory epilepsy in childhood?

Children with unilobar or multilobar pathology issuing in refractory epilepsy are potential candidates for surgical treatment. Extensive surgery results in good seizure control, but it also increases the risk of neurological deficits as well as motor and mental problems. We reviewed the cases of 19 children with refractory epilepsy treated surgically at Osaka University Hospital. Four of the 19 patients underwent temporal disconnection, 2 underwent occipital lobectomy, 4 underwent temporoparietooccipital disconnection, 6 underwent functional hemispherotomy, and 3 underwent corpus callosotomy. A good surgical outcome, i.e., Engel's class I or II, was achieved in 12 (63%) of the 19 patients. Excellent surgical outcomes and satisfactory motor and mental development were achieved in 4 patients who underwent temporoparietooccipital disconnection. The outcomes of functional hemispherectomy were also satisfactory. The outcomes of temporal disconnection and corpus callosotomy were poor in comparison to outcomes of the other procedures. We believe that better surgical outcomes would have been achieved with temporoparietooccipital disconnection in some cases treated by temporal disconnection or occipital resection. Adequate extensive surgical procedures should be considered for refractory childhood epilepsy arising from unilobar or multilobar pathology.

Current management and surgical outcomes of medically intractable epilepsy

Epilepsy is one of the most common neurologic disorders in the world. While anti-epileptic drugs (AEDs) are the mainstay of treatment in most cases, as many as one-third of patients will have a refractory form of disease indicating the need for a neurosurgical evaluation. Ever since the first half of the twentieth century, surgery has been a major treatment option for epilepsy, but the last 10-15 years in particular has seen several major advances. As shown in relatively recent studies, resection is more effective for medically intractable epilepsy (MIE) than AED treatment alone, which is why most clinicians now endorse a neurosurgical consultation after approximately two failed regimens of AEDs, ultimately leading to decreased healthcare costs and increased quality of life. Temporal lobe epilepsy (TLE) is the most common form of MIE and comprises about 80% of epilepsy surgeries with the majority of patients gaining complete seizure-freedom. As the number of procedures and different approaches continues to grow, temporal lobectomy remains consistently focused on resection of mesial structures such as the amygdala, hippocampus, and parahippocampal gyrus while preserving as much of the neocortex as possible resulting in optimum seizure control with minimal neurological deficits. MIE originating outside the temporal lobe is also effectively treated with resection. Though not as successful as TLE surgery because of their frequent proximity to eloquent brain structures and more diffuse pathology, epileptogenic foci located extratemporally also benefit from resection. Favorable seizure outcome in each of these procedures has heavily relied on pre-operative imaging, especially since the massive surge in MRI technology just over 20 years ago. However, in the absence of visible lesions on MRI, recent improvements in secondary imaging modalities such as fluorodeoxyglucose positron emission computed tomography (FDG-PET) and single-photon emission computed tomography (SPECT) have lead to progressively better long-term seizure outcomes by increasing the neurosurgeon's visualization of supposed non-lesional foci. Additionally, being historically viewed as a drastic surgical intervention for MIE, hemispherectomy has been extensively used quite successfully for diffuse epilepsies often found in pediatric patients. Although total anatomic hemispherectomy is not utilized as commonly today, it has given rise to current disconnective techniques such as hemispherotomy. Therefore, severe forms of hemispheric developmental epilepsy can now be surgically treated while substantially decreasing the amount of potential long-term complications resulting from cavitation of the brain following anatomical hemispherectomy. Despite the rapid pace at which we are gaining further knowledge about epilepsy and its surgical treatment, there remains a sizeable underutilization of such procedures. By reviewing the recent literature on resective treatment of MIE, we provide a recent up-date on epilepsy surgery while focusing on historical perspectives, techniques, prognostic indicators, outcomes, and complications associated with several different types of procedures.

Long-term developmental outcome after early hemispherotomy for hemimegalencephaly in infants with epileptic encephalopathy

This study aimed to identify the effect of early hemispherotomy on development in a consecutive series of 12 infants with hemimegalencephaly (HME) demonstrating epileptic encephalopathy. Mean age at onset was 20.4 days (range, 1-140), mean age at surgery was 4.3 months (range, 2-9), and mean follow-up time was 78.8 months (range, 36-121). Eleven patients had a history of early infantile epileptic encephalopathy. Vertical parasagittal hemispherotomy was performed without mortality or severe morbidities. At follow-up, seizure freedom was obtained in 8 patients (66.7%), who showed significantly higher postoperative developmental quotient (DQ) (mean, 31.3; range, 7-61) than those with seizures (mean, 5.5; range, 3-8) (p=0.02). Within the seizure-free group, postoperative DQ correlated with preoperative seizure duration (r=-0.811, p=0.01). Our results showed that shorter seizure duration during early infancy could provide better postoperative DQ in infants with HME and epileptic encephalopathy.

Hemispherectomy in adults patients with severe unilateral epilepsy and hemiplegia

OBJECTIVES

To study postoperative seizure control of hemispherectomy in adults with epilepsy and evaluate changes of movement and speech function, intelligence quotient (IQ) and quality of life (QOL) after hemispherectomy.

METHODS

We retrospectively analyzed 25 adults who presented severe unilateral epilepsy and hemiplegia and underwent anatomic or functional hemispherectomy in between 2006 and 2011. Surgical outcomes, including seizure-control at last follow-up, changes of aphasia quotient, hemiplegic side motor function, IQ and QOL from pre-operative to 2 years follow-up, were investigated. Results were statistically analyzed with SPSS 18.0.

RESULTS

Nine functional hemispherectomies and 16 anatomic hemispherectomies were performed. Ninety-two percent of patients were seizure-free and 8% displayed Engel II grade seizure control after the procedure. Impaired movement function was present in 9 (36%) adults' upper limbs and 5 (20%) patients' lower limbs. The patients with age at seizure onset <3 years showed improvement in mean motor function of the upper limbs. Impaired speech was seen in 7 patients with left hemispherectomies. There was an overall improvement in the mean aphasia quotient and significant difference was found in amount of change in aphasia quotients between patients with different ages of onset. All of the patients' postoperative scores of overall QOL, full IQ, verbal IQ and performance IQ improved compared with pretreatment scores and those improvements were not associated with patient's age at seizure onset or surgical approach. However, significant difference was found in change of verbal IQ between patients with right hemispherectomies and those with left hemispherectomies. Surgical complications included a single case of hydrocephalus, and 6 transient complications.

CONCLUSIONS

Hemispherectomy presented good seizure control and improvement in QOL and IQ, and impairment on motor and speech function were mild. Furthermore, patients with early seizure onset could maintain movement function of upper limb and speech function improvement. Therefore, it is worth pursuing hemispherectomy in well-selected adults with severe unilateral epilepsy and hemiplegia.

Seizure and developmental outcomes after hemispherectomy in children and adolescents with intractable epilepsy

PURPOSE

The aim of this study is to describe a series of pediatric hemispherectomies, reviewing pathologic substrate, epilepsy characteristics and seizure outcome as well as developmental profiles, before and after surgery, in different domains.

METHODS

Seventeen patients with full pre-surgical work-up, minimum follow-up of 12 months, and at least one post-surgical neuropsychological evaluation were selected. Three had Rasmussen encephalitis (RE), five hemispheric malformations of cortical development (MCD), and nine hemispheric vascular lesions.

RESULTS

At latest follow-up, all patients with RE and 66.7 % of those with vascular lesions are in Engel's class I; in the latter group, pre-surgical independent contralateral EEG discharges statistically correlated with a worse seizure outcome. Patients with MCD showed the worst seizure outcome. Pre-surgical language transfer to the right hemisphere was confirmed in a boy with left RE, operated on at 6 years of age. Patients with MCD and vascular lesions already showed severe global developmental delay before surgery, which persists afterwards. A linear correlation was found between earlier age at surgery and better outcome in personal-social, gross motor, and adaptive domains, in the vascular lesions group. The case with highest cognitive improvement had continuous spike and wave during sleep on pre-surgical EEG.

CONCLUSIONS

Pathologic substrate was the main factor related with seizure outcome. In children with MCD and vascular lesions, although developmental progression is apparent, significant post-surgical improvements are restricted by the severity of pre-surgical neuropsychological disturbances and a slow maturation. Early surgery assessment is recommended to enhance the possibilities for a better quality of life in terms of seizure control, as well as better autonomy and socialization.

Pediatric epilepsy surgery

Whereas there is no specific neurosurgical technique in pediatric epilepsy, the frequency of each type of surgery is very different from epilepsy surgery applied in adults, and reflects the underlying etiologies, which are much more diverse in children, with malformations of cortical development and tumors as the prevailing etiologies. Extensive resective or disconnective procedures for extratemporal epilepsy are more frequently performed in infants and younger children, whereas temporo-mesial resection is by far the most common surgical treatment for adults with epilepsy. More recently, less invasive techniques in children with an extensive epileptogenic zone, such as multilobar disconnection, hemispherotomy and other functional hemispherectomy variants, have been introduced in order to reduce duration of surgery, perioperative morbidity and length of hospital stay. Likewise, minimally invasive techniques are utilized, such as the endoscopic disconnection of hypothalamic hamartomas for gelastic epilepsy. This development has been encouraged with the introduction of image-guided navigation systems for the preoperative planning and during surgery. Historically, epilepsy surgery for children has been established much later than for adults. Apart from the particular aspects in perioperative management of younger infants, surgery-related morbidity as well as seizure outcome is in general similar to those in adults, depending rather on each type of surgery.

Focal epileptogenic lesions

The spectrum of focal epileptogenic lesions and their clinical manifestations in children differ substantially from those seen in adults. In adults, mesial temporal sclerosis is the common lesion in surgical series; but in children, MTS is uncommon, and when it does occur, it exists frequently as dual pathology. The most common lesions in pediatric epilepsy surgery candidates are malformations of cortical development, developmental tumors, or encephalomalacia from infarction, hypoxia, trauma, or infection. Careful analysis of the lesion characteristics on brain MRI is sufficiently predictive of pathology in most cases. Histopathological evaluation remains the gold standard for diagnosis of mass lesions. The electroclinical phenotype of epilepsy in adults is largely determined by the anatomical location of the lesion and its connectivity. In children, in addition to the location of the lesion, the age at onset of the lesion and the age at onset of epilepsy have a major impact on the electroclinical phenotype. Children with congenital or early acquired lesions may manifest with generalized features on EEG and seizure semiology. Experience from various centers has demonstrated that a subset of these children benefit from epilepsy surgery despite a generalized epilepsy phenotype. All children with medically refractory epilepsy and a focal lesion should undergo evaluation for potential epilepsy surgery irrespective of the EEG findings and seizure semiology.

Pediatric functional hemispherectomy: outcome in 92 patients

BACKGROUND

The revival of epilepsy surgery after the introduction of modern presurgical evaluation procedures has led to an increase in hemispherectomy or hemispherotomy procedures. Since a large part of our pediatric series was done using a newer hemispherotomy technique, we focus mainly on the outcomes after a recently developed hemispherotomy technique (transsylvian keyhole).

METHODS

Ninety-six pediatric patients (aged 4 months to 18 years, mean 7.3) were operated on between 1990 and 2009; 92 were available with follow-up.

RESULTS

The most frequent diagnosis was porencephaly in 46 % of all patients. Progressive etiologies were present in 20 % and developmental etiologies in 22 %. At last available outcome (LAO), 85 % of the patients were seizure free (ILAE class 1). Year-to-year outcome was rather stable; usually over 80 % were class 1 for up to 13 years (n = 24). Of 92 assessable patients, 71 were treated with the transsylvian keyhole technique, with 89 % being seizure free. The overall shunt rate was 5.3 % for the whole series and 3 % for the keyhole technique subgroup. Mortality was 1 of 96 patients. Excluding patients with hemimegalencephaly (HME), patients with the shortest duration of epilepsy and the lowest age at seizure onset had the highest rates of seizure freedom. The etiology does influence outcome, with HME patients having the poorest seizure outcome and patients with Sturge-Weber syndrome and porencephaly having excellent seizure control.

CONCLUSION

Hemispherotomies/functional hemispherectomies are very effective and safe procedures for treating drug-resistant epilepsy with extensive unihemispheric pathology. Etiology and surgery type clearly influence seizure outcome.

Outcomes of disconnective surgery in intractable pediatric hemispheric and subhemispheric epilepsy

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.

Craniosynostosis following hemispherectomy in a 2.5-month-old boy with intractable epilepsy

The authors report on the case of a 6-week-old boy who presented with infantile spasms. At 2.5 months of age, the patient underwent a right hemispherectomy. Approximately 3 months postoperatively, the patient presented with left coronal craniosynostosis. Subsequent cranial vault remodeling resulted in satisfactory cosmesis. Four years after surgery, the patient remains seizure free without the need for anticonvulsant medications. The authors believe this to be the first reported case of iatrogenic craniosynostosis due to hemispherectomy, and they describe 2 potential mechanisms for its development. This case suggests that, in the surgical treatment of infants with intractable epilepsy, minimization of brain volume loss through disconnection techniques should be considered, among other factors, when determining the best course of action.

[Disability and epilepsy]

The purpose of this article is to familiarize radiologists with the different aspects of severe drug resistant epilepsy. These result in three levels of disability: the disease itself (seizures and their impact, underlying cause), social impact (restrictions, safety and precautions, education, activities of daily life) and issues related to the medical treatment (long term medication intake, side effects, complications). First, clinical and EEG diagnosis will be reviewed to move on to MRI with attention to technical and protocol considerations followed by the imaging features of specific entities causing severe drug resistant epilepsy: migration and gyration disorders, Rasmussen's encephalitis, Sturge Weber disease and post-ischemic sequelae. Finally, current data and the imaging features of hemispherotomy, a radical treatment for epilepsy, will be presented.

Treatment of Rasmussen encephalitis half a century after its initial description: promising prospects and a dilemma

Rasmussen encephalitis (RE), initially described half a century ago, is an inflammatory unihemispheric brain disorder. Its two clinical key facets are the progressive tissue and function loss and the epilepsy, often in form of epilepsia partialis continua. For both, treatment options are available. Anti-seizure effect of anti-epilepsy drugs is usually limited to secondarily generalized seizures and complex partial seizures whereas epilepsia partialis continua usually is totally refractory. Hemispherectomy in one of its modern variants offers a very high chance of seizure freedom, however at the price of irreversible loss of functions located in the affected hemisphere. In a proportion of patients, long-term immunotherapy is able to prevent or slow down hemispheric tissue loss and the associated functional decline. It does, however, mostly not improve the epilepsy. Whereas for many patients unequivocal treatment proposals can be readily made, a dilemma may emerge in those with severe epilepsy but still preserved hemispheric function.

[CT and MR brain imaging following hemispherotomy]

PURPOSE

The aim of the study was to define the usual and pathological modifications arising in the brain following hemispherotomy for intractable epilepsy in children.

METHODS

Preoperative MRI and postoperative imaging scans (CT in the first week, MRI at 3 months and 1 year after surgery) were reviewed in a series of 52 patients, average age 8 years and 7 months, with intractable epilepsy due to dysplasia, Rasmussen's encephalitis, ischemic lesions and/or Sturge-Weber disease. The posterior fossa, brain parenchyma, ventricles and subdural space were also analyzed.

RESULTS

Hemispheric scarring was a typical finding on CT and MRI as a consequence of the surgical procedure. Also frequently seen were small subdural effusions, bleeding along the surgical scar on early CT, and chronic subdural effusions with no mass effect on mid-term and late MRI scans. Other features - such as large subdural effusions that required external shunts and hydrocephalus - were rare, but severe, and considered to be postoperative complications. In contrast to the complications associated with other surgical techniques such as hemispherectomy, infection, extensive edema or hemosiderosis were never found in our series.

CONCLUSION

Hemispherotomy is a surgical technique performed to treat intractable epilepsy. Our findings will help to identify the typical morphology of postsurgical scars, and to differentiate the usual features and complications seen in the postoperative period on CT and MRI brain scans.

Seizures continue even after prompt anti-epileptic drug medication in Sturge-Weber syndrome--study from prolonged video electrocoticography, a case report

INTRODUCTION

The mechanism of epilepsy in Sturge-Weber syndrome (SWS) has not been elucidated, since it is difficult to detect epileptic discharges on scalp EEG records. To determine the electrophysiological characteristics of SWS, we evaluated epileptic discharges using intracranial electrocorticography (ECoG).

CASE SUMMARY

We report a 1-year and 3-month-old boy diagnosed with SWS whose psychomotor development was impaired despite good control of his seizures with several antiepileptic drugs (AEDs). Prolonged video ECoG monitoring was performed to determine whether subclinical seizures had induced his developmental delay.

DISCUSSION

Frequent seizures were detected as motionless staring and respiratory distress. His seizures originated from multiple areas along the Sylvian fissure, propagated very slowly, and lasted for 10 to 30 min. Left hemispherotomy was performed, and he was confirmed to be completely seizure-free after surgery. Our findings indicate that long-lasting and barely discernible seizures may continue in patients with SWS who appear to have good control of epilepsy with AEDs.

[Surgical resections in functional areas: report of 89 cases]

Surgical resections for intractable epilepsy are generally associated with a high risk of permanent neurological deficit and a poor rate of seizure control. We present a series of 89 patients operated on from 1992 through 2007 for drug-resistant partial epilepsy, in whom surgery was performed in a functional area of the brain: the central (sensorimotor and supplementary motor areas) region in 48 cases, posterior regions (parietal and occipital) in 27, the insula in eight, and the language areas in six. Epilepsy was cryptogenic in 12 patients, and lesion-related in 77: malformation of cortical development in 43, tumor in 17, perinatal cicatrix in 13, vascular lesion in three, and another prenatal lesion in one. Seventy patients underwent stereoelectroencephalographic (SEEG) exploration. The surgical procedure was resective (lesionectomy or SEEG-guided corticectomy) in 83 patients and multiple stereotactic thermocoagulations in six. Ten patients were reoperated because of early seizure recurrence. A postoperative complication was observed in 12 patients. Postoperative deficits were observed in 54 patients (61%) and resolved completely in 29. In 25, a permanent deficit persisted, minor in 19 and moderate to severe in six, which did not correlate with localization or etiology. With a one-year follow-up in 74 patients (mean, 3.6 years), 53 (72%) were in Engel's class I, including 38 (51%) in class IA. Seizure outcome was significantly associated with etiology: 93% of Taylor-type focal cortical dysplasia, whereas only 40% of cryptogenic epilepsies were in class I (p<0.05). This suggests that resective or disconnective surgery for intractable partial epilepsy in functional areas of the brain may be followed by excellent results on seizures and a moderate risk of permanent neurological sequelae.