Hemispherectomy for the Treatment of Intractable Seizures in Childhood

Pediatric Neurostimulation and Practice Evolution

Since the late nineteenth century, the prevailing view of epilepsy surgery has been to identify a seizure focus in a medically refractory patient and eradicate it. Sadly, only a select number of the many who suffer from uncontrolled seizures benefit from this approach. With the development of safe, efficient stereotactic methods and targeted surgical therapies that can affect deep structures and modulate broad networks in diverse disorders, epilepsy surgery in children has undergone a paradigmatic evolutionary change. With modern diagnostic techniques such as stereo electroencephalography combined with closed loop neuromodulatory systems, pediatric epilepsy surgery can reach a much broader population of underserved patients.

Midline Brain Shift After Hemispheric Surgery: Natural History, Clinical Significance, and Association With Cerebrospinal Fluid Diversion

BACKGROUND

Hemispherectomy and its modern variants are effective surgical treatments for medically intractable unihemispheric epilepsy. Although some complications such as posthemispherectomy hydrocephalus are well documented, midline brain shift (MLBS) after hemispheric surgery has only been described anecdotally and never formally studied.

OBJECTIVE

To assess the natural history and clinical relevance of MLBS and determine whether cerebrospinal fluid (CSF) shunting of the ipsilateral surgical cavity exacerbates MLBS posthemispheric surgery.

METHODS

A retrospective review of consecutive pediatric patients who underwent hemispheric surgery for intractable epilepsy and at least 6 months of follow-up at UCLA between 1994 and 2018 was performed. Patients were grouped by MLBS severity, shunt placement, valve type, and valve opening pressure (VOP). MLBS was evaluated using the paired samples t-test and analysis of covariance adjusting for follow-up time and baseline postoperative MLBS.

RESULTS

Seventy patients were analyzed, of which 23 (33%) required CSF shunt placement in the ipsilateral surgical cavity for posthemispherectomy hydrocephalus. MLBS increased between first and last follow-up for nonshunted (5.3 ± 4.9-9.7 ± 6.6 mm, P < .001) and shunted (6.6 ± 3.5-16.3 ± 9.4 mm, P < .001) patients. MLBS progression was greater in shunted patients (P = .001). Shunts with higher VOPs did not increase MLBS relative to nonshunted patients (P = .834), whereas MLBS increased with lower VOPs (P = .001). Severe MLBS was associated with debilitating headaches (P = .048).

CONCLUSION

Patients undergoing hemispheric surgery often develop postoperative MLBS, ie, exacerbated by CSF shunting of the ipsilateral surgical cavity, specifically when using lower VOP settings. MLBS exacerbation may be related to overshunting. Severe MLBS is associated with debilitating headaches.

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.

SPECT-PET in Epilepsy and Clinical Approach in Evaluation

In epilepsy, a detailed history, blood chemistry, routine electroencephalography, and brain MRI are important for the diagnosis of seizure type or epilepsy syndrome for the decision of appropriate drug treatment. Although antiepileptic drugs are mostly successful for controlling epileptic seizures, 20%-30% patients are resistant to medical treatment and continue to have seizures. In this intractable patient group, surgical resection is the primarily preferred treatment option. This particular group of patients should be referred to the epilepsy center for detailed investigation and further treatment. When the results of electroencephalography, MRI, and clinical status are discordant or there is no structural lesion on MRI, ictal-periictal SPECT, and interictal PET play key roles for lateralization or localization of epileptic region and guidance for the subsequent subdural electrode placement in intractable epilepsy. SPECT and PET show the functional status of the brain. SPECT and PET play important roles in the evaluation of epilepsy sydromes in childhood by showing abnormal brain regions. Most of the experience has been gained with (18)FDG-PET, in this respect. (11)C-flumazenil-PET usually deliniates the seizure focus more smaller than (18)FDG-PET and is sensitive in identifying medial temporal sclerosis. (11)C-alpha-methyl-l-tryptophan is helpful in the differentiation of epileptogenic and nonepileptogenic regions in children especially in tuberous sclerosis and multifocal cortical dysplasia for the evaluation of surgery. Finally, when there is concordance among these detailed investigations, resective surgery or palliative procedures can be discussed individually.

Surgical Treatment of Epilepsy in Pediatric Patients

Surgery has become an accepted treatment modality for carefully selected adults with intractable focal epilepsy. More recently, increasing numbers of pediatric patients with intractable epilepsy are also being referred for surgical consideration. Key elements of surgical candidacy include medically intractable focal epilepsy, a localized epileptogenic zone, and a low risk for new postoperative neurologic deficits. The most common etiologies of the epilepsies in pediatric surgical candidates are malformation of cortical development and low grade tumor but some patients with childhood onset temporal lobe epilepsy due to hippocampal sclerosis also present for early surgery. Based on results from several recent pediatric surgical series, the chance for favorable seizure outcome after surgery is not adversely affected by young age, with seizure-free postoperative outcome reported for 60% to 65% of infants, 59% to 67% of children, and 69% of adolescents, compared to 64% reported in a large, predominantly adult series. Some subgroups of patients have higher percentages of seizure-free outcome, including those with hippocampal sclerosis or low grade tumor. In addition to seizures, developmental issues are also a major concern in children with intractable epilepsy. Few quantitative data are available, but some anecdotal experience suggests that surgical relief of catastrophic epilepsy may result in resumption of developmental progression after surgery, although the rate of development often remains abnormal. In one series, best developmental outcomes were seen in patients with earliest surgery and highest level of preoperative development. For each patient, the timing of surgery must be carefully considered, based on a full assessment of the relative risks and benefits, derived from a detailed presurgical evaluation.

Functional Hemispherectomy for Refractory Status Epilepticus in 2 Adults

BACKGROUND

Status epilepticus (SE) is a medical emergency, as deleterious long-term effects are well known. Medically induced burst suppression is often required if first-line and second-line treatments fail. Surgical intervention can be considered in some patients after prolonged treatment failure of medically induced coma. Multiple surgical options for terminating SE have been demonstrated in the literature, with only 2 reports including hemispherectomy in adults.

CASE DESCRIPTION

We present 2 cases of adults with refractory SE who failed more conservative medical/surgical treatment but responded to functional hemispherectomy. Pertinent electroencephalography and imaging findings are discussed. In addition, all previously published pediatric and adult cases are briefly reviewed.

CONCLUSIONS

Functional hemispherectomy can be considered in patients, including adults, with super-refractory SE and diffuse hemispheric onset. We report acceptable outcomes and quality of life in our 2 patients.

Utility of diffusion tensor imaging studies linked to neuronavigation and other modalities in repeat hemispherotomy for intractable epilepsy

OBJECT Hemispherectomy for unilateral, medically refractory epilepsy is associated with excellent long-term seizure control. However, for patients with recurrent seizures following disconnection, workup and investigation can be challenging, and surgical options may be limited. Few studies have examined the role of repeat hemispherotomy in these patients. The authors hypothesized that residual fiber connections between the hemispheres could be the underlying cause of recurrent epilepsy in these patients. Diffusion tensor imaging (DTI) was used to test this hypothesis, and to target residual connections at reoperation using neuronavigation. METHODS The authors identified 8 patients with recurrent seizures following hemispherectomy who underwent surgery between 1995 and 2012. Prolonged video electroencephalography recordings documented persistent seizures arising from the affected hemisphere. In all patients, DTI demonstrated residual white matter association fibers connecting the hemispheres. A repeat craniotomy and neuronavigation-guided targeted disconnection of these residual fibers was performed. Engel class was used to determine outcome after surgery at a minimum of 2 years of follow-up. RESULTS Two patients underwent initial hemidecortication and 6 had periinsular hemispherotomy as their first procedures at a median age of 9.7 months. Initial pathologies included hemimegalencephaly (n = 4), multilobar cortical dysplasia (n = 3), and Rasmussen's encephalitis (n = 1). The mean duration of seizure freedom for the group after the initial procedure was 32.5 months (range 6-77 months). In all patients, DTI showed limited but definite residual connections between the 2 hemispheres, primarily across the rostrum/genu of the corpus callosum. The median age at reoperation was 6.8 years (range 1.3-14 years). The average time taken for reoperation was 3 hours (range 1.8-4.3 hours), with a mean blood loss of 150 ml (range 50-250 ml). One patient required a blood transfusion. Five patients are seizure free, and the remaining 3 patients are Engel Class II, with a minimum follow-up of 24 months for the group. CONCLUSIONS Repeat hemispherotomy is an option for consideration in patients with recurrent intractable epilepsy following failed surgery for catastrophic epilepsy. In conjunction with other modalities to establish seizure onset zones, advanced MRI and DTI sequences may be of value in identifying patients with residual connectivity between the affected and unaffected hemispheres. Targeted disconnection of these residual areas of connectivity using neuronavigation may result in improved seizure outcomes, with minimal and acceptable morbidity.

The role of magnetoencephalography in children undergoing hemispherectomy

OBJECT

Hemispherectomy is an established neurosurgical procedure for medication-resistant epilepsy in children. Despite the effectiveness of this technique, there are patients who do not achieve an optimum outcome after surgery; possible causes of suboptimal results include the presence of bilateral independent epileptogenic foci. Magnetoencephalography (MEG) is an emerging tool that has been found to be useful in the management of lesional and nonlesional epilepsy. The authors analyzed the relative contribution of MEG in patient selection for hemispherectomy.

METHODS

The medical records of children undergoing hemispherectomy at the Hospital for Sick Children were reviewed. Those patients who underwent MEG as part of the presurgical evaluation were selected.

RESULTS

Thirteen patients were included in the study. Nine patients were boys. The mean age at the time of surgery was 66 months (range 10-149 months). Seizure etiology was Rasmussen encephalitis in 6 patients, hemimegalencephaly in 2 patients, and cortical dysplasia in 4 patients. In 8 patients, video-EEG and MEG results were consistent to localize the primary epileptogenic hemisphere. In 2 patients, video-EEG lateralized the ictal onset, but MEG showed bilateral spikes. Two patients had bilateral video-EEG and MEG spikes. Engel Class I, II, and IV outcomes were seen in 10, 2, and 1 patients, respectively. In 2 of the patients who had an outcome other than Engel Class I, the MEG clusters were concentrated in the disconnected hemisphere. The third patient had bilateral clusters and potentially independent epileptogenic foci from bilateral cortical dysplasia.

CONCLUSIONS

The presence of unilateral MEG spike waves correlated with good outcomes following hemispherectomy. In some cases, MEG provides information that differs from that obtained from video-EEG and conventional MR imaging studies. Further studies with a greater number of patients are needed to assess the role of MEG in the preoperative assessment of candidates for hemispherectomy.

Hemispherectomy for the control of intractable epilepsy in childhood: comparison of 2 surgical techniques in a single institution

BACKGROUND

Hemispherectomy is an established neurosurgical procedure for catastrophic epilepsy in childhood. However, the technique used to achieve an optimum outcome remains to be determined.

OBJECTIVE

We examined the influence of hemidecortication (HD) vs peri-insular hemispherotomy (PIH) on patient outcome.

METHODS

The medical records of 41 children undergoing hemispherectomy were reviewed for patient demographics, clinical criteria, and surgical outcomes.

RESULTS

HD and PIH were performed in 21 and 20 children, respectively. The mean age at surgery for HD was 54 months and 61 months for PIH. The median durations of surgery for HD and PIH were 5 hours and 7 hours, respectively (P < .001). For HD, 6 patients required a second surgery and 3 required a third. One PIH patient required a second procedure. Postoperative shunting was required in 5 HD patients, but only 1 PIH patient. All patients had increased hemiparesis after surgery. The overall mean follow-up time was 72 months. Engel class I or II outcomes after initial surgery were better after PIH (85%) compared with HD (48%) (P < .02). After subsequent surgeries for seizure control, 4 HD patients and 1 PIH patient improved to Engel class I or II.

CONCLUSION

Hemispherectomy is an effective surgical procedure for childhood intractable catastrophic epilepsy. In patients with diffuse hemispheric disorder, PIH tends to have fewer major complications, more favorable seizure outcomes, and a decreased need for subsequent surgical procedures, including shunting for hydrocephalus, compared with HD.

Approach to pediatric epilepsy surgery: State of the art, Part I: General principles and presurgical workup

In 1990, the National Institute of Health adopted epilepsy surgery in children as an option when medications fail. In the past few years several concepts have become increasingly recognized as key to a successful approach to epilepsy surgery in children. These include the concepts of neuronal plasticity, the epileptogenic lesion, the ictal onset, symptomatogenic, irritative, and epileptogenic zones. In addition, several techniques have increasingly been utilized to delineate the above areas in an attempt to determine, in each patient, the epileptogenic zone, defined as the zone the resection of which leads to seizure freedom. When seizure semiology (which defines the symptomatogenic zone), ictal EEG (which identifies the ictal onset zone), and structural imaging (which identifies the epileptogenic lesion) can be reconciled to infer the location of the epileptogenic zone, surgery is usually, subsequently, undertaken. When these diagnostic modalities are discordant, not definitive, or when the epileptogenic zone is close to eloquent cortex, invasive EEG, complemented by other imaging techniques may be needed. These include magnetoencephalography, single photon emission tomography, various types of positron emission tomography, various magnetic resonance imaging modalities (functional, diffusion weighted, other) and other emerging and experimental techniques. While MRI, video-EEG, and neuropsychological assessments are well established components of the presurgical evaluation, the use of the new emerging imaging technologies is dictated by the degree of anatomo-electro-clinical correlations, and, awaiting multicentric studies and more detailed guidelines, remains center-dependent.

Role of external ventriculostomy in the management of fever after hemispherectomy

OBJECT

Fever is a common occurrence after cerebral hemispherectomy in children and prolongs the hospital stay. The authors determined whether an external ventriculostomy might reduce the incidence of fever following a hemispherectomy.

METHODS

The postoperative courses of 27 patients who had undergone cerebral hemispherectomy for intractable seizures were retrospectively analyzed.

RESULTS

Thirteen children underwent an external ventriculostomy, and only 1 had an elevated axillary body temperature of > or = 39 degrees C during the postoperative period. Among 14 patients who did not undergo an external ventriculostomy, 7 had a posthemispherectomy fever of > or = 39 degrees C. Patients who underwent an external ventriculostomy had a lower risk of postoperative fever compared with those who did not undergo the procedure (8 vs 50%, respectively; p = 0.03, Fisher exact test). None of the patients had an infection accounting for the cause of the fever. The hospital stay for patients who had undergone postoperative external ventriculostomy was significantly shorter than for those who had not (7.2 +/- 2 vs 11.3 +/- 5 days, respectively; p = 0.01, Student t-test).

CONCLUSIONS

The use of external ventriculostomy following hemispherectomy for intractable epilepsy in children reduces the incidence of postoperative fever due to infection.

Nano neurology and the four P's of central nervous system regeneration: preserve, permit, promote, plasticity

True nanomaterials are delivered as a specific structure, or combination of structures, designed to deliver the therapeutic intact, directly to the site, requiring a much lower dose. These materials use very specific and deliberate molecular structures that can interact with neurons or protein structures inside the cells. Until recently, functional recovery of the central nervous system (CNS) was an unattainable goal and nanotechnology was an invisible science. A well-planned treatment spaced over time will produce functional return in the CNS. The four P's of CNS regeneration is a new framework for approaching CNS injury and evidence shows that nanotechnology is currently being used for stroke rehabilitation and, in several clinical trials, the treatment of scar formation blockade in the spinal cord. The four components are preserve, permit, promote, and plasticity.

Hemispherectomy for intractable epilepsy in adults: The first reported series

Hemispherectomy for intractable unihemispheric epilepsy (IUE) has long been established in pediatric patients. This study reports the first series examining hemispherectomy exclusively in adult patients (>18 years old). Nine adults with IUE underwent hemispherectomy at the University of Minnesota. All patients had unilateral hemiplegia and visual field loss. Seven patients (77.8%) were Engel class I/II at last follow-up. Five (83.3%) of the six patients with >30 years of follow-up were seizure free. No surgery-related mortality, hydrocephalus, or superficial cerebral hemosiderosis occurred. Hemispherectomy is an effective procedure in appropriately selected adult patients, resulting in excellent long-term seizure control and no mortality.

Cognitive assessment in epilepsy surgery of children

INTRODUCTION

Although the neurocognitive assessment in children as in the adults is an important step before and after surgery, in the literature, the data about pre- and postoperative neurocognitive evaluations in children are very few.

OBJECTIVE

The purpose of this paper is to consider some peculiar aspects of the neurocognitive assessment during development, and report literature data about neuropsychological outcome of epileptic children treated with focal resection and hemispherectomy.

RESULTS AND DISCUSSION

The second section concerns our personal experience about a cohort of 45 children with refractory epilepsy operated on before 7 years. The results suggest that early surgical treatment is generally effective for seizure control and behavior improvement in children with refractory epilepsy. Concerning cognitive outcome, we found that the neurocognitive level was unchanged in the majority of the patients.

CONCLUSION

We underline the importance of multicentric studies with standardized neuropsychological assessments in large series of young children.

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.

Predictive validity in a prospective follow-up of PTSD in preschool children

OBJECTIVE

To examine the predictive validity of an alternative to the DSM-IV for diagnosing posttraumatic stress disorder (PTSD) in preschool children and prospectively explore the course of PTSD symptomatology.

METHOD

Sixty-two traumatized children, ages 20 months through 6 years, were assessed three times in 2 years with caregiver diagnostic interviews.

RESULTS

PTSD diagnosis at visit 1 significantly predicted degree of functional impairment 1 and 2 years later and predicted PTSD diagnosis 2 years later but not 1 year later. The lack of 1-year diagnostic continuity may be explained by children with new traumas. Unexpectedly, overall PTSD symptoms did not remit over time, regardless of community treatment; however, reexperiencing symptoms decreased and avoidance/numbing symptoms increased with time, with avoidance/numbing symptoms increasing at a faster rate in children with PTSD at visit 1. The previous finding that arousal may cause emotional numbing was not replicated. Significantly more children were functionally impaired at visits 2 (48.9%) and 3 (74.3%) than were diagnosed with PTSD (23.4% and 22.9%, respectively).

CONCLUSIONS

This study demonstrates predictive validity for the alternative method of diagnosing PTSD in preschool children. The unremitting course of PTSD symptomatology in preschool children and rates of impairment that are higher than rates of diagnosis indicate the need for efficacious treatment.

Hemispherotomy: description of surgical technique

INTRODUCTION

Hemispherectomy constitutes an established surgical method in the management of patients with medically intractable epilepsy, secondary to severe unilateral hemisphere damage. The well-established association of the anatomical hemispherectomy initially described with severe complications such as late hydrocephalus has led to the development of less resective and more disconnecting procedures. All these technical variations of hemispherotomy carry less favorable outcomes compared with anatomic hemispherectomy, but significantly fewer complications.

METHODS

In our current communication, we outline the indications and the surgical technique of hemispherotomy and report our experience of the clinical application of this surgical procedure.

RESULTS

In our clinical series, the 5-year follow-up shows that 66.6% of our patients (6 out of 9) had class I outcome according to Engel's classification system, 22.2% (2 out of 9) class II outcome, while 11.1% (1 out of 9) had class III outcome. No mortality occurred in the current series and operative blood loss was significantly lowered.

CONCLUSION

Hemispherotomy represents a less efficacious technique compared with anatomic hemispherectomy, but is a safe and technically simple surgical alternative for the management of patients with medically intractable seizures.

Treatment of Refractory Status Epilepticus with Hemispherectomy

A 7-year-old boy with left hemiparesis secondary to right hemispheric cortical dysplasia was admitted to the hospital with increasing numbers of seizures. Magnetic resonance imaging showed a small dysplastic right hemisphere with abnormally thickened gyri and an apparently normal left hemisphere. Previous video-electroencephalogram (EEG) monitoring showed bilateral independent spikes and generalized slow spike-and-wave episodes on EEG and [18F]fluorodeoxyglucose (FDG) positron emission tomography scan demonstrated scattered areas of regional hypometabolism bilaterally; therefore hemispherectomy was not undertaken at that time. During this hospital stay, nonconvulsive status epilepticus developed and was refractory to multiple medical therapies including pentobarbital (PTB) coma. Burst-suppression pattern during PTB coma appeared to be generalized spike and wave, but when EEG was reviewed with increased time resolution spikes suggested a right hemisphere origin. The patient underwent bilateral intracarotid amobarbital spike-suppression test that showed only minimal suppression of epileptiform discharges with injection of the left carotid, but complete suppression of spike activity after right-sided carotid injection. A right hemispherectomy was performed with complete cessation of status epilepticus. Postoperative EEG showed no epileptiform discharges. Patient follow-up was limited to 12 months after surgery. The patient had regained the ability to walk unaided and was seizure free with a single antiepileptic medication. This case illustrates a potentially life-saving procedure for refractory status epilepticus and several techniques including a spike-suppression test to aid in prediction of cessation of seizures after hemispherectomy.

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.

Mental retardation in pediatric candidates for epilepsy surgery: the role of early seizure onset

PURPOSE

We sought to determine whether early age at seizure onset is a risk factor for mental retardation, independent of etiology. Assessment of risk for mental retardation with continued uncontrolled seizures plays a role in considerations of timing for epilepsy surgery. Previous studies have indicated that onset of seizures in the first years of life may be a risk factor for mental retardation, but the etiologies of the epilepsies were not included in the analyses.

METHODS

Intellectual function was assessed at ages 2-20 years during presurgical evaluation in 100 patients with intractable epilepsy due to focal lesions limited to part of one lobe of the brain. Mental retardation (MR) was defined as Full-Scale Intelligence Quotient (FSIQ) < or =70. The age at seizure onset and the seizure frequency were obtained retrospectively.

RESULTS

Younger ages at seizure onset were associated with lower FSIQ scores, and mean FSIQ was also significantly lower for patients with onset of epilepsy at < or =24 months of age (74.0 +/- 21.5) versus that in patients with onset of epilepsy later in life (87.8 +/- 18.8; p = 0.005). The frequency of patients with MR was significantly higher for patients with seizure onset at < or =24 months of age (15 of 33, 46%) than for patients with seizure onset later in life (eight of 67, 12%; p < 0.001). This difference persisted within etiologic subgroups. For patients with focal malformation of cortical development, MR was seen in eight (50%) of 16 patients with seizure onset at < or =24 months versus two (10%) of 20 patients with seizure onset at >24 months (p < 0.001); for patients with tumor, MR was seen in four (50%) of eight patients with seizure onset at < or =24 months versus four (13%) of 30 patients with seizure onset at >24 months (p = 0.003); and for patients with hippocampal sclerosis, MR was seen in two (28%) of seven patients with seizure onset at < or =24 months versus none of 30 patients with seizure onset at >24 months (NS). Within the subgroup with daily seizures, MR was present in 13 (65%) of 20 patients with seizure onset at < or =24 months versus five (17%) of 29 patients with seizure onset later in life (p = 0.001).

CONCLUSIONS

These results indicate that onset of intractable epilepsy within the first 24 months of life is a significant risk factor for MR, especially if seizures occur daily. The risk based on early age at seizure onset appeared independent of etiology and persisted within subgroups of patients with focal malformation of cortical development, tumor, or hippocampal sclerosis. Prospective studies will be important to clarify whether early surgical intervention may reduce the risk for subsequent MR in carefully selected infants.

Epilepsy surgery in children with developmental disabilities

Surgery for treatment of medically uncontrolled epilepsy in children is now widely accepted with reported outcomes similar to those in adults. Epilepsy is reported in 8.8% to 32% of children with mental retardation (MR) and in up to half of children with severe retardation. There has been concern that patients with low IQ will experience unsatisfactory outcomes from epilepsy surgery and not achieve good seizure control. It is appropriate to reassess the prior bias against resective epilepsy surgery in children with MR in view of the changing criteria for potential candidacy for epilepsy surgery in infants and young children. There are three prerequisites for epilepsy surgery: (1) the epilepsy must be medically intractable; (2) the surgery must be feasible, that is, the epileptogenic zone can identified and safely resected; and (3) there is high likelihood of a satisfactory outcome as regards both the epilepsy and the patient's functional status. Patients with MR may have diffuse cerebral dysfunction and diffuse or multifocal epileptogenic regions. Appropriate patient selection is made possible through use of current technology that allows identification of lesions or areas of cerebral dysgenesis, aiding in identification of localized areas of epileptogenesis. Results from various series of patients with MR who have undergone resective surgery for epilepsy have shown that with careful presurgical evaluations, outcomes are similar between patients with normal IQ scores and those with low scores. Surgical protocols specifically for patients with MR and intractable epilepsy are required, including careful definition of desired outcomes.

Disability evaluation in children with hemidecorticectomy: use of the activity scales for kids and the pediatric evaluation disability inventory

The purpose of this study is to investigate the level of disability of children who are either candidates for or have undergone a hemidecorticectomy. The Activity Scales for Kids and the Pediatric Evaluation Disability Inventory were demonstrated to be useful measurement tools yielding comparative results between subgroups. Overall, children with congenital disease seemed less autonomous postoperatively than were preoperative patients or children with acquired disease. Age at surgery and the interval between seizure onset and surgery are potentially important predictors of disability. This could reflect the importance of timing of surgery, development, environment, and possibly brain plasticity processes in this population.

The significance of bilateral EEG abnormalities before and after hemispherectomy in children with unilateral major hemisphere lesions

The rate of seizure relief following hemispherectomy varies between 50 and more than 80%. There has been particular debate concerning the significance of bilateral electroencephalography (EEG) abnormalities in influencing prognosis. This study was set out to determine the frequency of bilateral EEG abnormalities and their relationship to underlying pathology and outcome. We investigated 28 children with unilateral hemisphere lesions, who underwent hemispherectomy. Interictal and ictal EEGs before and after hemispherectomy were reviewed. Post-operative outcome with respect to seizures was noted. Bilateral EEG abnormalities were seen in 75%, but were more common in children with malformations of cortical development than in patients with acquired cerebral lesions, and were found more often in interictal than in ictal records. Post-operative EEG abnormalities were variable and did not consistently predict outcome. Short-term outcome was similar, irrespective of aetiology. With longer term follow-up, only 47% of children with developmental abnormalities were still seizure-free in contrast to 77% of children with acquired abnormalities. Although the incidence of bilateral EEG abnormalities in patients with major unilateral hemisphere lesions is high, these findings alone should not preclude further consideration for hemispherectomy. Our findings emphasise that the aetiology of the lesion plays a major role in determining outcome.

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.