Cerebral hemicorticectomy for epilepsy

Hemispherotomy Revised: A complication overview and a systematic review meta-analysis

Introduction

Hemispherectomy/hemispherotomy has been employed in the management of catastrophic epilepsy. However, initial reports on the associated mortality and morbidity raised several concerns regarding the technique's safety. Their actual, current incidence needs to be systematically examined to redefine hemispherotomy's exact role.

Research question

Our current study examined their incidence and evaluated the association of the various hemispherotomy surgical techniques with the reported complications.

Material & methods

A PRISMA-compliant systematic review and meta-analysis was performed. We searched PubMed, Scopus, and Web of Science until December 2022. Fixed- and random-effects models were employed. Egger's regression test was used for estimating the publication bias, while subgroup analysis was utilized for defining the role of the different hemispherotomy techniques.

Results

We retrieved a total of 37 studies. The overall procedure mortality was 5%, with a reported mortality of 7% for hemispherectomy and 3% for hemispherotomy. The reported mortality has decreased over the last 30 years from 32% to 2%. Among the observed post-operative complications aseptic meningitis and/or fever occurred in 33%. Hydrocephalus requiring a shunt insertion occurred in 16%. Hematoma evacuation was necessary in 8%, while subgaleal effusion in another 8%. Infections occurred in 11%. A novel post-operative cranial nerve deficit occurred in 11%, while blood transfusion was necessary in 28% of the cases.

Discussion and conclusion

Our current analysis demonstrated that the evolution from hemispherectomy to hemispherotomy along with neuroanesthesia advances, had a tremendous impact on the associated mortality and morbidity. Hemispherotomy constitutes a safe surgical procedure in the management of catastrophic epilepsies.

Hemispherotomy for Epilepsy: The Procedure Evolution and Outcome

Hemispherectomy is a unique epilepsy surgery procedure that has undergone significant modification and evolution since Dandy's early description. This procedure is mainly indicated to treat early childhood and infancy medically intractable epilepsy. Various epileptic syndromes have been treated with this procedure, including hemimegalencephaly (HME), Rasmussen's encephalitis, Sturge-Weber syndrome (SWS), perinatal stroke, and hemispheric cortical dysplasia. In terms of seizure reduction, hemispherectomy remains one of the most successful epilepsy surgery procedures. The modification of this procedure over many years has resulted in lower mortality and morbidity rates. HME might increase morbidity and lower the success rate. Future studies should identify the predictors of outcomes based on the pathology and the type of hemispherectomy. Here, based on a literature review, we discuss the evolution of hemispherectomy techniques and their outcomes and complications.

A new model of experimental hemispherotomy in young adult Rattus norvegicus: a neural tract tracing and SPECT in vivo study

OBJECTIVE

The objective of this study was to describe a new experimental model of hemispherotomy performed on laboratory animals.

METHODS

Twenty-six male young adult Wistar rats were distributed into two groups (surgery and control). The nonfluorescent anterograde neurotracer biotinylated dextran amine (BDA; 10,000 MW) was microinjected into the motor cortex area (M1) according to The Rat Brain in Stereotaxic Coordinates atlas to identify pathways and fibers disconnected after the experimental hemispherectomy. SPECT tomographic images of 99mTc hexamethylpropyleneamine oxime were obtained to verify perfusion in functioning areas of the disconnected and intact brain. A reproducible and validated surgical procedure is described in detail, including exact measurements and anatomical relationships. An additional 30 rodents (n = 10 rats per group) were divided into naïve, sham, and hemispherotomy groups and underwent the rotarod test.

RESULTS

Cortico-cortical neural pathways were identified crossing the midline and contacting neuronal perikarya in the contralateral brain hemisphere in controls, but not in animals undergoing hemispherotomy. There was an absence of perfusion in the left side of the brain of the animals undergoing hemispherotomy. Motor performance was significantly affected by brain injuries, increasing the number of attempts to maintain balance on the moving cylinder in the rotarod test at 10 and 30 days after the hemispherotomy, with a tendency to minimize the motor performance deficit over time.

CONCLUSIONS

The present findings show that the technique reproduced neural disconnection with minimal resection of brain parenchyma in young adult rats, thereby duplicating the hemispherotomy procedures in human patients.

Hemispheric surgery for refractory epilepsy: a systematic review and meta-analysis with emphasis on seizure predictors and outcomes

OBJECT

Conflicting conclusions have been reported regarding several factors that may predict seizure outcomes after hemispheric surgery for refractory epilepsy. The goal of this study was to identify the possible predictors of seizure outcome by pooling the rates of postoperative seizure freedom found in the published literature.

METHODS

A comprehensive literature search of PubMed, Embase, and the Cochrane Library identified English-language articles published since 1970 that describe seizure outcomes in patients who underwent hemispheric surgery for refractory epilepsy. Two reviewers independently assessed article eligibility and extracted the data. The authors pooled rates of seizure freedom from papers included in the study. Eight potential prognostic variables were identified and dichotomized for analyses. The authors also compared continuous variables within seizure-free and seizure-recurrent groups. Random- or fixed-effects models were used in the analyses depending on the presence or absence of heterogeneity.

RESULTS

The pooled seizure-free rate among the 1528 patients (from 56 studies) who underwent hemispheric surgery was 73%. Patients with an epilepsy etiology of developmental disorders, generalized seizures, nonlateralization on electroencephalography, and contralateral MRI abnormalities had reduced odds of being seizure-free after surgery.

CONCLUSIONS

Hemispheric surgery is an effective therapeutic modality for medically intractable epilepsy. This meta-analysis provides useful evidence-based information for the selection of candidates for hemispheric surgery, presurgical counseling, and explanation of seizure outcomes.

Intact intracranial breast prosthesis: a 28-year CT follow-up after treatment of late hemispherectomy complications

Anatomical hemispherectomy has had excellent results in treating drug-resistant seizures of infantile hemiplegia. This technique of hemispherectomy consists in the removal of a whole hemisphere, with or without the basal ganglia, the end result being a large cavity left at the end of the operation. The technique, however, is considered to be weighted by important complications, in particular intracranial hemorrhages due to vessels tearing secondary to dislodgement of the remaining hemisphere. Several techniques have been consequently proposed to reduce the volume of the residual hemicranial cavity. An alternative measure is the filling of the cavity itself. We have demonstrated that this type of procedure can be carried out using a silicone breast prosthesis. In this report, we demonstrate also that such an implant can have a surprisingly long duration in its unusual location.

Hemispherotomy and other disconnective techniques

The surgical treatment of intractable epilepsy has evolved as new technical innovations have been made. Hemispherotomy techniques have been developed to replace hemispherectomy in order to reduce the complication rates while maintaining good seizure control. Disconnective procedures are based on the interruption of the epileptic network rather than the removal of the epileptogenic zone. They can be applied to hemispheric pathologies, leading to hemispherotomy, but they can also be applied to posterior quadrant epilepsies, or hypothalamic hamartomas. In this paper, the authors review the literature, present an overview of the historical background, and discuss the different techniques along with their outcomes and complications.

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

OBJECTIVE

Hemispherotomy techniques have been developed to reduce complication rates and achieve the best possible seizure control. We present the results of our pediatric patients who underwent vertical parasagittal hemispherotomy and evaluate the safety and global long-term outcome of this technique.

METHODS

Eighty-three patients underwent vertical parasagittal hemispherotomy by the same neurosurgeon (OD) between 1990 and 2000. We reviewed all patients between 2001 and 2003 for a standard global evaluation. The general principle is to achieve, through a posterior frontal cortical window, the same line of disconnection as performed with the classic hemispherectomy, while leaving the majority of the hemisphere intact along with its afferent and efferent vascular supply.

METHODS

Seventy-four percent of the patients were seizure-free; among them, 77% were seizure-free without further drug treatment. Twelve percent rarely had seizures (Engel Class II) and 14% continued to have seizures (Engel Class III or IV). The results varied according to the etiology, but this variation was not statistically significant. The early postoperative course was uneventful for 94% of the children, and shunt placement was necessary in 15%. We found a correlation between the preoperative delay and the Vineland Adaptive Behavior score: children with a longer duration of seizures had lower performances.

CONCLUSION

Vertical parasagittal hemispherotomy is an effective surgical technique for hemispheric disconnection. It allows complete disconnection of the hemisphere through a cortical window with good results in terms of seizure outcome and a comparably low complication rate.

Peri-insular hemispherotomy in paediatric epilepsy

OBJECTS

Outline the indications, investigation, surgical technique, pitfalls, complications and benefits of peri-insular hemispherotomy (PIH) in the surgical treatment of paediatric epilepsy.

MATERIALS AND METHODS

This report is based on a consecutive series of 43 children who underwent PIH. Sixty percent were males; there were slightly more left-sided surgeries. Median interval between seizure onset and surgery was 5 years. In more than half the cases, the anatomical substrate was congenital. There were few complications: one death, one hydrocephalus and two anatomically remote haemorrhages. Ninety percent of the patients have remained in Engel's class I epilepsy outcome.

CONCLUSIONS

There are clear indications for hemispherectomy in children. In some instances of incomplete deficit, timing of surgery remains a major concern. The less invasive approach to eliminate the influence of the diseased hemisphere, in our opinion, is with disconnective techniques of hemispherectomy, and among the latter, peri-insular hemispherotomy provides, in our opinion, the best complications-benefits ratio.

Hemimegalencephaly: clinical implications and surgical treatment

INTRODUCTION

Hemimegalencephaly (HME) is a quite rare malformation of the cortical development arising from an abnormal proliferation of anomalous neuronal and glial cells that generally leads to the hypertrophy of the whole affected cerebral hemisphere. The pathogenesis of such a complex malformation is still unknown even though several hypotheses are reported in literature.

BACKGROUND

HME can occur alone or associated with neurocutaneous disorders, such as neurofibromatosis, epidermal nevus syndrome, Ito's hypomelanosis, and Klippel-Trenonay-Weber syndrome. The clinical picture is usually dominated by a severe and drug-resistant epilepsy. Other common findings are represented by macrocrania, mean/severe mental retardation, unilateral motor deficit, and hemianopia. The EEG shows different abnormal patterns, mainly characterized by suppression burst and/or hemihypsarrhythmia. Although neuroimaging and histologic investigations often show typical findings (enlarged hemisphere, malformed ventricular system, alteration of the normal gyration), the differential diagnosis with other disorders of the neuronal and glial proliferation may be difficult to obtain. Hemispherectomy/hemispherotomy is the most effective treatment to control seizure, and it also seems to provide good results on the psychomotor development when performed early, as demonstrated by the literature review and by the reported personal series reported here (20 children). The surgical therapy of HME, however, is still burdened by a quite high complication rate and mortality risk.

Anatomical hemispherectomy

INTRODUCTION

Anatomical hemispherectomy is frequently employed in the surgical management of pediatric patients with medically refractory epilepsy.

MATERIALS AND METHODS

In this chapter, we review the historical evolution of this surgical procedure, outline the indications and the criteria for selecting surgical candidates and describe the important pre-operative evaluation of the surgical candidates.

DISCUSSION

We provide a detailed description of our surgical technique, anesthesiological considerations, and post-operative care plan. Ultimately we analyze the most common complications associated with this procedure.

CONCLUSION

Anatomical hemispherectomy performed in carefully selected pediatric patients with medically intractable epilepsy can be a safe and efficacious surgical procedure.

Hemispherectomy: a schematic review of the current techniques

Anatomical hemispherectomy has been used for the treatment of seizures since 1938. However, it was almost abandoned in the 1960s after reports of postoperative fatalities caused by hydrocephalus, hemosiderosis, and trivial head traumas. Despite serious complications, the remarkable improvement of patients encouraged authors to carry out modifications on anatomical hemispherectomy in order to lessen its morbidity while preserving its efficacy. The effort to improve the technique generated several original procedures. This paper reviews current techniques of hemispherectomy and proposes a classification scheme based on their surgical characteristics. Techniques of hemispherectomy were sorted into two major groups: (1) those that remove completely the cortex from the hemisphere and (2) those that associate partial cortical removal and disconnection. Group 1 was subdivided into two subgroups based on the integrity of the ventricular cavity and group 2 was subdivided into three subgroups depending on the amount and location of the corticectomy. Grouping similar techniques may allow a better understanding of the distinctive features of each one and creates the possibility of comparing data from different authors.

Presurgical evaluation and surgical treatment of medically refractory epilepsy

Thanks to today's modern imaging examination techniques and especially to the common use of intracranial electrodes for localizing seizure foci, more and more patients with partial epilepsy can be treated microsurgically. The results of such neurosurgical therapies are very good, particularly in mesial temporal lobe epilepsy. In recent years, good results (60-70% seizure freedom) have also been achieved in extratemporal epilepsy surgery, so that such procedures can now be recommended for carefully selected patients. In this review, presurgical evaluations and the different surgical approaches are presented.

Hemispherectomy techniques

Hemispherectomy techniques have undergone multiple changes. Because of these changes, several current alternatives are described. The need for an extensive procedure in young children with special pediatric requirements is the background for the development of newer and more microsurgically oriented techniques aimed at reducing the intraoperative problems and late postoperative complications. This article reviews the strengths and the disadvantages of the currently used procedures in light of special requirements for hemispheric dysplasias.

Transsylvian keyhole functional hemispherectomy

OBJECTIVE

To describe the technical steps, advantages, and limitations of a quicker, minimal-exposure, functional hemispherectomy procedure developed from a hemispherical deafferentation technique previously described.

METHODS

The surgical approach using the transsylvian/transsulcal passage to the ventricular system, with the anatomic orientation points and key features for planning of the small trepanation, is described. Through a linear incision, a craniotomy (4 x 4 to 4 x 5 cm) is placed over the sylvian fissure. Transsylvian exposure of the circular sulcus allows transcortical exposure of the entire ventricular system, from the frontal horn to the temporal horn encircling the insular cortex. The frontobasal and mesial white matter is disconnected via the intraventricular approach, with a callosotomy. An amygdalohippocampectomy completes the dissection. The experience with 20 patients who were treated using the transsylvian keyhole hemispherectomy technique is summarized.

RESULTS

The operation time was significantly shorter (mean, 3.6 h) than with the Rasmussen technique (mean, 6.3 h) and 25% shorter than with the transcortical perisylvian technique (mean, 4.9 h). The proportion of patients requiring blood replacements was lower (15 versus 58%), as was the mean amount of transfused blood. The mean follow-up period was 46 months; 88% of patients were in Engel Outcome Class I, 6% in Class III, and 6% in Class IV.

CONCLUSION

The transsylvian keyhole procedure has been demonstrated to further reduce operation time and the need for blood replacement. It is most easily performed in cases with enlarged ventricles or perinatal ischemic cysts and is not recommended for hemimegalencephaly. The immediate seizure relief was satisfying. This minimal-exposure approach seems to be a satisfying alternative among possible functional hemispherectomy procedures.

Modification of peri-insular hemispherotomy and surgical results

OBJECTIVE

We modified the peri-insular hemispherotomy technique devised by Villemure and Mascott. Our modified technique and the surgical results obtained with this method are presented.

METHODS

The frontoparietal operculum is resected, and the resection cavity is connected with the lateral ventricle. Through this cavity, a transventricular corpus callosotomy and resection of the medial temporal structures are performed.

RESULTS

This technique was used for 34 patients, with satisfactory surgical results. Cerebrospinal fluid shunt placement was necessary for five patients, and incomplete callosal sectioning was postoperatively detected in three cases.

CONCLUSION

Our modification of the peri-insular hemispherotomy can be safely and effectively used to treat epilepsy caused by hemispheric lesions, even in cases without ventricular dilation.

Surgical treatment of epilepsy in children

In carefully selected children, as well as adults, intractable seizures may be eliminated or greatly reduced by cortical resection or hemispherectomy. Critical features of surgical candidacy include intractable disabling epilepsy, a localized epileptogenic zone, and a low risk of new postoperative deficits; however, the analysis may be complicated in children. Compared with adults, pediatric patients are especially likely to present with poorly localizing electroencephalographic features because of their high incidence of extratemporal localization and developmental pathology. Maturation factors may result in unusual epilepsy manifestations, for example, infantile spasms and hypsarrhythmia caused by a focal cortical lesion. The cognitive and psychosocial costs of continued frequent seizures during infancy and childhood must be assessed differently from those in adults and may include stagnation of developmental progression. The risk for new postoperative deficits may be modified if surgery is performed during stages of active brain maturation with developmental plasticity. For each individual child, the potential risk/benefit ratio for surgery must be carefully weighed on the basis of results of an extensive preoperative evaluation. Results from pediatric epilepsy surgery series are encouraging, with percentages of seizure-free patients similar to those in adult series. In some series, delaying surgery for childhood-onset epilepsy into adulthood was associated with greater permanent psychosocial, behavioral, and educational problems. The available data suggest that children should be considered for surgical evaluation at whatever age they present with severe intractable localization-related epilepsy. Complicated cases warrant referral to specialized centers with extensive pediatric epilepsy surgery experience.

Ultrasound-tailored functional hemispherectomy for surgical control of seizures in children

Functional hemispherectomy techniques have been designed to minimize the long-term complications of anatomical resection without reducing the effectiveness of seizure control. The authors have used an ultrasound-guided approach tailored to combine temporal lobectomy with frontal and occipital disconnections with a central topectomy of the lateral, insular, and interhemispheric cortex. This technique achieves a comprehensive functional disconnection and minimizes entrance and manipulation within the body of the lateral ventricle. Eight patients ranging in age from 10 months to 23 years with congenital paresis and medically intractable seizures underwent functional hemispherectomy via this technique. The average surgical time was 4.5 hours, and blood loss ranged from 90 to 400 ml. All but one patient was discharged after 5 days. Postoperative fever syndromes, aseptic meningitis, and infection were avoided. On long-term follow-up evaluation (range 18-60 months, mean 38 months), seven of eight patients remain seizure free and were not on a course of anticonvulsant agents. Advantages of this technique include avoiding entrance into the ventricle, a more predictable postoperative period, and reduced postoperative complications.

Hemispherectomy for intractable seizures in children: a report of 58 cases

Fifty-eight children who underwent anatomical, functional, or modified anatomical hemispherectomy for intractable seizures from 1986 to 1995 were evaluated for seizure control, motor function, and complications. Age at surgery ranged from 0.3 to 17.3 years (median 2.8 years). Twenty-seven anatomical, 27 functional, and 4 modified anatomical hemispherectomies were performed. Seizure control and motor function in the 50 patients with more than 1 year follow-up revealed a 90% or better reduction in seizure frequency in 44/50 (88%) overall: 19/22 (86%) anatomical, 23/26 (89%) functional, and 2/2 modified anatomical. Motor function of the preoperatively hemiparetic extremities was improved or unchanged postoperatively in 38/50 (76%) of the patients. Complications included one intraoperative death, one late death from shunt obstruction managed elsewhere, late postoperative seizure breakthrough requiring reoperation and further disconnection in 5/27 functional hemispherectomy patients, mild cerebrospinal fluid infections in 3/27 anatomical hemispherectomy patients, and hydrocephalus requiring shunting in 3/27 functional hemispherectomy patients. A review of the literature and comparison of techniques is presented.

Hemispherectomy: a hemidecortication approach and review of 52 cases

Between 1975 and 1994, 52 hemispherectomies, of which two were anatomical and 50 hemidecortications, were performed at Johns Hopkins Medical Institutions. Eighteen patients were 2 years old or less. There were three perioperative mortalities and one patient died 9 months later from causes not related to surgery. One patient developed hydrocephalus 6 years postsurgery and has been treated effectively. Seizure control and the functional status of each patient were measured as outcome variables. Forty-six (96%) of the surviving patients were seizure free or had reduced seizures as of their last follow-up examination. Twenty-one individuals (44%) were participating in age-appropriate classes or working independently, 18 were classified as semiindependent, and nine children will likely depend on a lifetime of assisted living. The relationships between the outcome variables and the patient's age at surgery, the interval to surgery, and the etiology of the disease were compared. The authors' clinical experiences strongly suggest the importance of a multidisciplinary approach to patient selection and follow-up care. Moreover, anesthetic management of infant surgery is a major component of success.

Intractable epilepsy in children

Although most children with epilepsy have a good prognosis, a small but significant minority have seizures that either do not respond to conventional antiepileptic drugs (AEDs) or have significant adverse reactions to AEDs. Many children may benefit from epilepsy surgery. Surgical treatment of epilepsy is becoming a well-established therapy for infants and young children with severe, medically intractable seizures. As in older children and adults, the presurgical evaluations of possible surgical candidates typically consist of a detailed history, neurologic and neuropsychologic examination, and anatomic and functional neuroimaging. The "gold standard" test, however, is the recording of ictal events by using simultaneous EEG and videomonitoring. Although temporal lobe resection is the most commonly performed surgery in older children and adults, nontemporal lobe resection, corpus callosotomy, and hemispherectomy are commonly performed in younger children. Efficacy of surgery in children compares favorably with results from adult patients. In addition, because the immature brain is more plastic than the mature brain, recovery of function is often greater after surgery in children than in adults. Early surgery in children with intractable epilepsy is recommended.

Peri-insular hemispherotomy: surgical principles and anatomy

THE NATURE OF functional hemispherectomy continues to be misunderstood despite its 20-year history. Recently, we introduced the concept of peri-insular hemispherotomy, a functional hemispherectomy with minimal brain removal (9, 21). To avoid additional confusion, a detailed neuroanatomic account of this operation, which has been performed in 11 patients, is presented. The name of the operative variant presented derives from the central importance of the exposure of the insula as the first surgical landmark. Incising along the circular sulcus that surrounds the insula not only allows access to the dilated ventricular system but also disrupts the entire internal capsule. A parasagittal callosotomy is performed from within the lateral ventricle by incising the medial ventricular roof. Projections through the anterior commissure are disrupted at the time of radical amygdalar resection. The posterior hippocampus need not be radically removed, because its posterior transsection disconnects it. Overall, peri-insular hemispherotomy can be viewed as a radical hemispheric tractotomy, resulting in a completely disconnected hemisphere. Advantages include shorter operative times, a less stormy postoperative course, and better anatomic preservation of the operated hemisphere, thus presumably reducing long-term complications.

EEG prior to hemispherectomy: correlation with outcome and pathology

Hemispherectomy, for the treatment of seizures, is highly successful but has a significant morbidity rate. The procedure is usually restricted to patients with an intractable seizure disorder and hemiparesis. Because of the inherent risk of surgery, patient selection is a critical issue. This report describes the evaluation of background activity and ictal patterns on surface and invasive EEG in 12 children who underwent both anatomical (7) and functional (5) hemispherectomy in order to determine the role of electroencephalography in the selection of patients for hemispherectomy, and to correlate EEG findings with underlying pathology and outcome. A favorable outcome was predicted by an interictal EEG with two or more of the following: suppression over the abnormal hemisphere, absence of contralateral slowing, absence of generalized discharges and absence of bilateral independent spiking; or by unilateral onset of ictal discharges on invasive intracerebral EEG recording. Outcome did not correlate with the underlying pathology. Hemispherectomy can be successful in patients with a variety of predominantly unilateral pathologic entities.

Hemispherical deafferentation: an alternative to functional hemispherectomy

An alternative technique for so-called functional hemispherectomy has been developed to be used for the classical indications of hemispherectomy or the various modifications of functional hemispherectomy. The technique entails a smaller trepanation, less operation time, and less blood loss, and it leaves more brain tissue in place as compared with other functional hemispherectomy techniques. It starts with either hippocampectomy alone or with hippocampectomy and anterior temporal lobectomy. After this, deafferentation of the white matter of the temporal, occipital, parietal, and frontal lobe, using either a transcortical transventricular approach along the outline of the lateral ventricle or a sylvian key hole approach, is performed. The technique includes a transventricular callosotomy, and it leaves in place only a small portion of the suprainsular cortex and the insular cortex. However, as one modification, removal of the insular cortex can easily be performed, if necessary, and, as a second modification, the entire transventricular deafferentation can be performed through a sylvian key hole. In this report, the technique is described and the surgical experience for the first 13 patients is outlined. The immediate seizure relief with an average follow-up of 12 months was similar to that for patients with functional hemispherectomy, but the follow-up period for these 13 patients is not long enough to allow definite conclusions concerning long-term control of seizures and long-term complications.

Technetium-99m HmPAO brain SPECT and outcome of hemispherectomy for intractable seizures

With recent descriptions of the modified hemispherectomies and hemicorticectomy, there has been renewed interest in hemispherectomy for treatment of intractable seizures with hemiparesis. Because long-term outcome remains uncertain, patient selection remains difficult. 99mTc-HmPAO brain SPECT has been a helpful adjunct in the evaluation of epilepsy surgery candidates. We report SPECT scan findings in 7 patients who underwent hemispherectomy and compare these results with scalp EEG findings. Six patients had unilateral SPECT findings and all had a favorable outcome, regardless of surface EEG findings.

Recent advances in childhood epilepsy

Recent advances in pediatric epileptology are the consequence of the explosive advance of medical technology in recent years. In this manuscript, some of the major highlights of these technology driven advances will be presented. Recognition of a typical EEG spike pattern leads to the identification of benign focal epilepsy of childhood, an extremely frequent electro-clinical syndrome of excellent prognosis. The development of CT scan and particularly of high resolution MRI, has led to the easy identification of a variety of pathologies which were previously recognized only by pathologists. These include, among others, neuroblast migrational disorders, mesial temporal sclerosis, forme fruste of tuberous sclerosis, and slow growing small temporal neoplasms. PET scanning has also shown to be particularly sensitive in the detection of subtle pathological lesions, which may remain undetected by MRI. This is particularly true in infants in whom the PET scan may uncover an unsuspected focal lesion in patients with hypsarrhythmia, indicating that hypsarrhythmia may be a form of a secondary generalized epilepsy. Advances in surgical techniques have also decreased significantly the risks of callosotomies and hemispherectomies, techniques that are now widely used to improve seizure control in patients with catastrophic seizure disorders. A better understanding of neurotransmitters involved in the generation or inhibition of seizures has led to the development of a variety of new drugs which promise to improve our ability to control seizures conservatively. Finally, advances in molecular biology have also had an impact on epileptology, leading to the discovery of gene abnormalities underlying a number of epileptic syndromes.