Modified hemispherectomy for epilepsy: early results in 10 cases

The hidden face of hemispherectomy: Visuo-spatial and visuo-perceptive processing after left or right functional hemispherectomy in 40 children

Functional hemispherectomy results in good outcomes in cases of refractory epilepsy and constitutes a unique situation in which to study cerebral plasticity and the reorganization of lateralized functions of the brain, especially in cases of infancy or childhood surgery. Previous studies have highlighted the remarkable ability of the brain to recover language after left hemispherectomy. This leads to a reorganization of language networks toward right hemisphere, causing limitation in the development of visuo-spatial abilities, known as a crowding effect in the right hemisphere. Deficits in nonverbal functions have also been described as a more direct consequence of right hemipherectomy, but the results from case studies have sometimes been contradictory. We conducted a group study which may effectively compare patients with left and right hemispherectomy and address the effects of the age of seizure onset and surgery. We analyzed the general visuo-spatial and visuo-perceptive abilities, including face and emotional facial expression processing, in a group of 40 patients aged 7-16 years with left (n = 24) or right (n = 16) functional hemispherectomy. Although the groups did not differ, on average, in general visuo-spatial and visuo-perceptive skills, patients with right hemispherectomy were more impaired in the processing of faces and emotional facial expressions compared with patients with left hemispherectomy. This may reflect a specific deficit in the perceptual processing of faces after right hemispherectomy. Results are discussed in terms of limited plasticity of the left hemisphere for facial and configural processing.

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.

Functional reorganization after hemispherectomy in humans and animal models: What can we learn about the brain's resilience to extensive unilateral lesions?

Hemispherectomy (HS) is an effective surgical procedure aimed at managing otherwise intractable epilepsy in cases of diffuse unihemispheric pathologies. Neurological recovery in subjects treated with HS is not limited to seizure reduction, rather, sensory-motor and behavioral improvement is often observed. This outcome highlights the considerable capability of the brain to react to such an extensive lesion, by functionally reorganizing and rewiring the cerebral cortex, especially early in life. In this narrative review, we summarize the animal studies as well as the human neurophysiological and neuroimaging studies dealing with the reorganizational processes that occur after HS. These topics are of particular interest in understanding mechanisms of functional recovery after brain injury. HS offers the chance to investigate contralesional hemisphere activity in controlling ipsilateral limb movements, and the role of transcallosal interactions, before and after the surgical procedure. These post-injury neuroplastic phenomena actually differ from those observed after less extensive brain damage. Therefore, they illustrate how different lesions could lead the contralesional hemisphere to play the "good" or "bad" role in functional recovery. These issues may have clinical implications and could inform rehabilitation strategies aiming to improve functional recovery following unilateral hemispheric lesions. Future studies, involving large cohorts of hemispherectomized patients, will be necessary in order to obtain a greater understanding of how cerebral reorganization can contribute to residual sensorimotor, visual and auditory functions.

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.

Endoscopy-Assisted Interhemispheric Transcallosal Hemispherotomy

BACKGROUND:

Various hemispherotomy techniques have been developed to reduce complication rates and achieve the best possible seizure control.

OBJECTIVE:

To present a novel and minimally invasive endoscopy-assisted approach to perform this procedure.

METHODS:

Endoscopy-assisted interhemispheric transcallosal hemispherotomy was performed in 5 children (April 2013-June 2014). The procedure consisted of performing a small craniotomy (4 × 3 cm) just lateral to midline using a transverse skin incision. After dural opening, the surgery was performed with the assistance of a rigid high-definition endoscope, and bayoneted self-irrigating bipolar forceps and other standard endoscopic instruments. Steps included a complete corpus callosotomy followed by the disconnection of the hemisphere at the level of the basal nuclei and thalamus. The surgeries were performed in a dedicated operating room with intraoperative magnetic resonance imaging and neuronavigation. Intraoperative magnetic resonance imaging confirmed a total disconnection.

RESULTS:

The pathologies for which surgeries were performed included sequelae of middle a cerebral artery infarct (n = 2), Rasmussen syndrome (n = 1), and hemimegalencephaly (2). Four patients had an Engel class I and 1 patient had a class II outcome at a mean follow-up of 10.2 months (range, 3-14 months). The mean blood loss was 80 mL, and mean operating time was 220 minutes. There were no complications in this study.

CONCLUSION:

This study describes a pilot novel technique and the feasibility of performing a minimally invasive, endoscopy-assisted hemispherotomy.

Hemispherectomy for treatment of refractory epilepsy in the pediatric age group: a systematic review

OBJECT

Evidence in support of hemispherectomy stems from a multitude of retrospective studies illustrating individual institutions' experience. A systematic review of this topic, however, is lacking in the literature.

METHODS

A systematic review of hemispherectomy for the treatment of refractory epilepsy available up to October 2013 was performed using the following inclusion criteria: reports of a total of 10 or more patients in the pediatric age group (≤ 20 years) undergoing hemispherectomy, seizure outcome reported after a minimum follow-up of 1 year after the initial procedure, and description of the type of hemispherectomy. Only the most recent paper from institutions that published multiple papers with overlapping study periods was included. Two reviewers independently applied the inclusion criteria and extracted all the data.

RESULTS

Twenty-nine studies with a total of 1161 patients met the inclusion criteria. Seizure outcome was available for 1102 patients, and the overall rate of seizure freedom at the last follow-up was 73.4%. Sixteen studies (55.2%) exclusively reported seizure outcomes of a single type of hemispherectomy. There was no statistically significant difference in seizure outcome and type of hemispherectomy (p = 0.737). Underlying etiology was reported for 85.4% of patients with documented seizure outcome, and the overall distribution of acquired, developmental, and progressive etiologies was 30.5%, 40.7%, and 28.8%, respectively. Acquired and progressive etiologies were associated with significantly higher seizure-free rates than developmental etiologies (p < 0.001). Twenty of the 29 studies (69%) reported complications. The overall rate of hydrocephalus requiring CSF diversion was 14%. Mortality within 30 days was 2.2% and was not statistically different between types of hemispherectomy (p = 0.787).

CONCLUSIONS

Hemispherectomy is highly effective for treating refractory epilepsy in the pediatric age group, particularly for acquired and progressive etiologies. While the type of hemispherectomy does not have any influence on seizure outcome, hemispherotomy procedures are associated with a more favorable complication profile.

Cognitive outcome after epilepsy surgery in children

The ultimate goal of epilepsy surgery in young children is to stop seizures, interrupt the downhill course of the epileptic encephalopathy, and improve developmental capacities. Postoperative outcome after childhood epilepsy surgery should therefore not only be expressed in terms of seizure freedom, cognitive outcome is an equally important outcome measure. Insight in the mutually dependent variables that can determine pre and postoperative cognitive developmental abilities will improve prediction of outcome and presurgical counseling of parents. The purpose of this review is to discuss the literature regarding cognitive outcome and the predictors of postoperative cognitive functioning after epilepsy surgery in children, particularly those with "catastrophic" epilepsy. There are only few studies in which the relation between possible determinants and cognitive outcome or change was statistically tested in a multivariable manner. Duration of epilepsy, presurgical Developmental Quotient (DQ) or Intelligence Quotient (IQ), and postoperative seizure freedom were the only factors reported in different studies to be independently related to eventual cognitive outcome after epilepsy surgery. Underlying etiology, gender, age at surgery, presurgical DQ/IQ, postoperative seizure freedom, cessation of antiepileptic medication, and follow-up interval have all been described in different surgical cohorts to be independently related to a postoperative change of IQ or DQ scores. To appreciate how each of the pre-epileptic, presurgical, and postoperative variables may independently influence eventual cognitive outcome and postoperative cognitive improvement, we need multicenter studies with large homogenous surgical populations, using standardized tests and multivariable analyses.

Periinsular hemispherotomy in children with stroke-induced refractory epilepsy

OBJECT

Ischemic cerebral vascular accidents (CVAs) in children result in epilepsy in 25% of patients, which is refractory in 7% of cases. Repeated seizures worsen the global and cognitive prognosis of these patients. To evaluate the prognosis of epilepsy and cognitive development in children with refractory seizures following a CVA, the authors retrospectively studied the effectiveness of periinsular hemispherotomy in the treatment of these patients.

METHODS

Between March 1995 and November 2007, 8 children who suffered from stroke-induced refractory epilepsy underwent a periinsular hemispherotomy. All patients' charts were reviewed in a retrospective manner. Age at the time of the CVA, imaging studies, cause of the ischemic event, onset of the first seizure, patient's handedness, the extent of the parenchymal damage, electroencephalography findings, type of epileptic seizures, number of seizures per day, number of antiepileptic medications, preoperative neuropsychological evaluation, and surgical outcome with regard to the patient's seizure activity were analyzed.

RESULTS

There were 7 boys and 1 girl in this study. The mean age at stroke was 23 months (range birth-5 years). The mean age at onset of epilepsy was 22 months (range 0-60 months). The mean age at the time of the hemispherotomy was 7 years (range 54-130 months). The average delay prior to the hemispherotomy was 5 years and 3 months (range 23-115 months). Prior to surgery, the average number of seizures per day was 35 (range 5-100). The average number of antiepileptic medications introduced before the hemispherotomy was 8 (range 6-12). Six patients required only 1 surgical intervention and 2 necessitated 2 separate operations:1 underwent a 2-staged hemispherotomy and the other underwent a prior callosotomy. There were no reported surgical complications in this series. Seven children are seizure free. However, the remaining child, after a 3.5-year disease-free interval, has recently started having seizures. No child demonstrated an improvement in neuropsychological evaluation.

CONCLUSIONS

The periinsular hemispherotomy must be considered an alternative in the therapeutic approach to stroke-induced pediatric refractory epilepsy. It is effective in controlling seizure activity. The authors believe the delay before hemispherotomy must be shortened in children with post-CVA refractory epilepsy.

Ipsilesional and contralesional sensorimotor function after hemispherectomy: differences between distal and proximal function

Previous studies have reported mainly on contralesional somatosensory and motor function after hemispherectomy. So far, ipsilesional impairments have received little attention even though these have been reported in patients with less extensive lesions. In the current study we assessed ipsilesional and contralesional sensorimotor function in a group of 12 patients with hemispherectomy. In addition, we focused on differences between distal and proximal function and investigated several factors that may have contributed to individual differences between patients. The tests included tapping, force production, tactile double simultaneous stimulation, pressure sensitivity, passive joint movement sense and sensitivity to hot and cold. Ipsilesional impairments were found on all tests, except passive joint movement sense. Unexpectedly, no significant ipsilateral distal-proximal gradient was found for any of the measures. Both the removal of the diseased cerebral hemisphere and possible changes to the remaining brain structures may have affected ipsilesional sensorimotor function. Contralesional performance was impaired on all tests except for passive joint movement in the shoulder. The contralesional impairments were characterized by a distal-proximal gradient measured on all tests, except that of sensitivity to hot and cold. Distal function was always most impaired. The difference between distal and proximal motor function is in agreement with the established concepts of the motor pathways, with the motoneurons innervating proximal muscles receiving bilateral cortical and subcortical input. Age at onset of original brain damage correlated significantly with passive joint movement sense. Patients with known abnormalities to the remaining brain structures performed inferior on the tapping test only. No effect was found of the hemispheric side of removal.

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.

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.

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 for intractable seizures: excellent seizure control, low morbidity and no superficial cerebral haemosiderosis

OBJECTIVE

This current study was performed to evaluate whether superficial cerebral haemosiderosis (SCH) is still a complication of modern day anatomical hemispherectomy.

METHODS

We report a 13-year institutional experience with anatomical hemispherectomy for intractable epilepsy. Seizure control at a mean follow-up interval of 7 years was 83%. Though one patient died post-operatively from a non-neurosurgical complication, mortality was otherwise zero and morbidity minimal. The much-described complication of SCH following anatomical hemispherectomy was non-existent. We explain the history of SCH as a complication of anatomical hemispherectomy, and the measures that are presently taken to prevent it.

CONCLUSIONS

We suggest that the importance of SCH in modern epilepsy surgery is probably over-emphasised.

Postsurgical Outcome in Pediatric Patients with Epilepsy: A Comparison of Patients with Intellectual Disabilities, Subaverage Intelligence, and Average-Range Intelligence

PURPOSE

Intellectual disabilities are often associated with bilateral or diffuse morphologic brain damage. The chances of becoming seizure free after focal surgery are therefore considered to be worse in patients with intellectual disabilities. The risk of postoperative cognitive deficits could increase because diffuse brain damage lowers the patient's ability to compensate for surgically induced deficits. Several studies in adult patients have indicated that IQ alone is not a good predictor of postoperative cognitive and seizure outcome. Our study evaluated this subject in children and adolescents.

METHODS

Pediatric patients with intellectual disabilities (IQ < or = 70), subaverage intelligence (IQ between 71 and 85), or average-range intelligence (IQ > 85) were matched according to several clinical and etiologic criteria to determine the influence of IQ (N = 66).

RESULTS

No dependency of seizure outcome, postoperative cognitive development, and behavioral outcome on the IQ level was found. All groups slightly improved in attention while memory functions tended to decrease and executive functions were stable. School placement remained unchanged for the majority of patients. Between 67 and 78% were seizure free 1 year after surgery (Engel outcome class I).

CONCLUSIONS

IQ alone is not a good predictor of postoperative outcome in pediatric patients with epilepsy. As with patients of average-range intelligence, the decision to operate on patients with a low level of intelligence should depend on the results of the presurgical diagnostics. If the results of the neuropsychological examination indicate diffuse functional impairment, this should not hinder further steps, if all other findings are consistent.

Developmental plasticity after right hemispherectomy in an epileptic adolescent with early brain injury

OBJECTIVES

The authors present the case of an adolescent affected with refractory epilepsy due to a neonatal ischemic infarction of the right medial cerebral artery. Hemiplegic since the first months of life, she began presenting motor partial seizures associated with drop attacks at 4.5 years; these were initially well controlled by antiepileptic drugs, but at 10 years seizures appeared again and became refractory. Thus, at 14 years and 10 months, she was submitted to a right hemispherectomy that made her rapidly seizure free. In the post-surgical follow-up lasting 5 years, neuropsychological serial assessments showed an impressive progressive improvement of cognitive skills, namely, visuospatial abilities. This case seems to challenge the widely spread feeling that functional catch-up in brain-injured children could only occur early in life. In effect, the astonishing recovery especially of visuospatial skills in our case occurred in adolescence after a late surgical intervention of right hemispherectomy.

METHODS

Different neuropsychological aspects are discussed. The reorganisation process recovered the spatial and linguistic abilities as well as the verbal and visuospatial memory; however, there was a persistent impairment of complex spatial and perceptual skills as well as recall abilities. Despite the deficit of complex visual stimuli processing, the patient showed a good performance in the recognition of unknown faces.

CONCLUSIONS

Probably, the absence of seizures in the first 4 years of life could have allowed a generally adequate compensatory reorganisation, successively masked by the persistent and diffuse epileptic disorder. The seizure control produced by surgery eventually made evident the effectiveness of the brain reorganisation.

Two-year follow-up of intelligence after pediatric epilepsy surgery

Research findings concerning cognitive effects of pediatric epilepsy surgery form an important basis for decisions about surgery. However, most follow-up studies have been of limited duration. In this study, a 2-year follow-up of intelligence was undertaken. Risk factors were analyzed. Included were 38 patients aged 3 to 17 years. Surgery was left in 19 patients and right in 19 patients. Types of surgery included temporal lobe resection (n = 23), extratemporal or multilobar resection (n = 8), and hemispherectomy (n = 7). The Wechsler Scales of Intelligence were administered presurgically, 6 months postsurgically, and 2 years postsurgically. No significant change in verbal or performance intelligence quotient (IQ) was demonstrated on a group level. Lateralization, type of surgery, age at surgery, sex, and presurgical IQ did not affect outcome. Across assessments, IQ scores of left-hemisphere patients were lower than those of right-hemisphere patients. Scores of patients in the hemispherectomy group were lower than those of the extratemporal or multilobar resection group, which were lower than the temporal lobe resection group. Scores improved significantly in six patients and deteriorated in seven. In conclusion, epilepsy surgery in children and adolescents does not, in general, have a significant impact on cognitive development in a 2-year perspective. In individual patients, poor seizure control and extensive surgery for Rasmussen's encephalitis were related to a deterioration of IQ.

Long-term follow-up in children with functional hemispherectomy for Rasmussen's encephalitis

INTRODUCTION

Cerebral hemispherectomy has been performed for over 60 years. Multiple variations of functional hemispherectomy have been performed since its inception by Rasmussen. Long-term follow-up for these variations is lacking in the medical literature.

METHODS

We review the long-term follow-up for five children with Rasmussen's encephalitis who underwent a modification of functional hemispherectomy.

RESULTS

The length of follow-up for this cohort ranged from 13 to 23 years (mean 15.6 years). All patients experienced immediate and complete elimination of seizures. Only one patient underwent ventriculoperitoneal shunt placement. All patients are capable of ambulating on their own. Many years following their procedures, this cohort of patients remains seizure free.

The Cognitive Outcome of Hemispherectomy in 71 Children

PURPOSE

Long-term neuropsychological outcome was studied in 71 patients who underwent hemispherectomy for severe and intractable seizures at The Johns Hopkins Hospital between 1968 and 1997 and who agreed to participate. Seizures were due to cortical dysplasias (n = 27), Rasmussen syndrome (n = 37), or vascular malformations or strokes (n = 7). Both presurgical and follow-up results are available and reported for 53 patients.

METHODS

Patients and caretakers were interviewed, and patients were administered standard measures of intelligence, receptive and expressive language, visual-motor skills, adaptive/developmental functioning, and behavior.

RESULTS

Mean age at surgery was 7.2 years. At follow-up, on average 5.4 years after surgery, 65% are seizure free, 49% are medication free, and, of those responding, none rated quality of life as worse than before surgery. Mean IQ was in the 70s for Rasmussen and vascular patients and in the 30s for cortical dysplasia patients. Language and visual-motor skills were consistent with IQ. For Rasmussen patients only, language was significantly more impaired for left than for right hemispherectomy, both before surgery and at follow-up. Adaptive skills were mildly impaired, with greatest impairment in the physical domain. Cognitive measures typically changed little between surgery and follow-up, with IQ change <15 points for 34 of 53 patients; of the remainder, 11 declined and eight improved. Behavior was free of major problems, but social interactions and activities were limited.

CONCLUSIONS

The most significant predictor of cognitive skills at follow-up was etiology, with dysplasia patients scoring lowest in intelligence and language but not in visual-motor skills. Regardless of etiology, most patients showed only moderate change in cognitive performance at follow-up.

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.

The role of light scatter in the residual visual sensitivity of patients with complete cerebral hemispherectomy

Various residual visual capacities have been reported for the phenomenally blind field of hemispherectomized patients, providing evidence for the relative roles of cortical and subcortical pathways in vision. We attempted to characterize these functions by examining the ability of five patients to detect, localize, and discriminate high-contrast flashed, flickering and moving targets. Dependent measures were verbal, manual, and oculomotor responses. As a control for light scatter, intensity thresholds for monocular detection of targets in the hemianopic field were compared with thresholds obtained when using an additional half eyepatch to occlude the blind hemiretina of the tested eye. One unilaterally destriate patient was tested on the same tasks. In photopic conditions, none of the hemispherectomized patients could respond to visual cues in their impaired fields, whereas the destriate patient could detect, discriminate, and point to targets, and appreciate the apparent motion of stimuli across his midline. Under reduced lighting, the threshold luminance required by hemispherectomized patients to detect stimuli presented monocularly was similar to that required for their detection when all visual information was occluded in the blind field, and only available to the visual system indirectly via light scatter. In contrast, the destriate patient's monocular threshold in his blind field was substantially lower than that for stimuli directly occluded in the blind field. As we found no range of stimuli which the hemispherectomized patients could detect or discriminate that was not also associated with discriminable scattered light, we conclude that the subcortical pathways which survive hemispherectomy cannot mediate voluntary behavioural responses to visual information in the hemianopic field.

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.

The effects of epilepsy surgery on the sensorimotor function of children

The motor and sensory functions of 50 children were investigated before and six months after epilepsy surgery; 34 infants were assessed 24 months after surgery. Postoperatively, 20 children were seizure-free and 22 had a significant reduction of seizures. Epilepsy surgery was found to be an effective mode of treatment for intractable seizures in childhood, even in multiply handicapped individuals. Motor and sensory functions did not deteriorate after surgery; in fact, significant improvements were found in more than half of the children, including those with multiple handicaps. Improvements were most obvious in the seizure-free group, but were also noted in those with reduced seizure frequency. The younger children benefited more from surgery as regards sensorimotor function than did older children and adolescents.

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.

Hemispherectomy for intractable seizures: long-term results in 17 patients followed for up to 38 years

Seventeen patients who underwent hemispherectomy for intractable epilepsy between 1950 and 1971 were reviewed to evaluate outcome for seizure control and the development of late complications. Sixteen had complete resection and in one the frontal pole was preserved. The follow-up period was 19 to 38 years (mean 28 years). One patient was lost to follow-up review 10 years after surgery. Three patients had died but none of the deaths were related to the surgery or to epilepsy. Ten patients had no postoperative complications, and three developed late complications: two had elevated intracranial pressure with enlargement of the remaining lateral ventricle after 13 and 16 years, and one had recurrent bleeding into the cerebrospinal fluid after 6 years. All were treated surgically and have since remained well. Eight patients (47%) had no seizures after surgery and eight (47%) were almost seizure-free. It is concluded that classical hemispherectomy is an effective operation for control of some types of epilepsy. The late complications, which occurred in 17% of the cases in this series, can be successfully treated. This series presents the longest follow-up results after hemispherectomy reported to date.

The surgery for epilepsy with speech arrest

The problems confronting patients with epilepsy, their families, and the surgeons wishing to help such patients, are discussed. It is important for physicians in other specialties to realize that epilepsy surgery is not nowadays complex, difficult, painful or uncertain; furthermore such operations are based on finding and removing focal lesions rather than "epileptogenic cortex" and the result in terms of integration of the patient into society is much improved if such intervention is performed while the patient is young, with time to gain academic and social skills after the operation. The selection of patients suitable for operation is discussed as well as methods of determining which hemisphere is dominant for speech and whether or not the focal lesion involves language centres. The majority of patients with drug resistant epilepsy suitable for operation have abnormalities in one temporal lobe. The pathological lesion is described and the advantages and disadvantages of various operations for temporal lobe epilepsy discussed. Extra-temporal cortical resection in the dominant hemisphere is also considered, particularly with reference to the preservation of language function. It is important that neurosurgeons realise that MRI and CT scanning have transformed epilepsy surgery from being a rather nebulous, time consuming art, to being for the majority of patients, a clear cut, straight forward procedure firmly based on "Oslerian" pathological principles. Far too few patients are being offered an operation (which renders 60-70% seizure free); neurosurgeons should respond to this challenge.

Neuropathologic findings in cortical resections (including hemispherectomies) performed for the treatment of intractable childhood epilepsy

Despite the use of hemispherectomy in the treatment of medically refractory seizures since the early 1950's, few studies published have documented neuropathologic findings in the resected specimens. This report describes the neuropathologic findings in 38 children who underwent either hemispherectomy or multilobar cortical resection as treatment for medically intractable epilepsy between 1986 and 1990. Examination of the resected specimens revealed a variety of abnormalities which fell into four broad categories. Malformations or hamartomatous lesions were the dominant finding in 15 patients, whereas encephalomalacic lesions were the most prominent abnormality in 16; chronic pathogen-free encephalitits (Rasmussen's encephalitis) was present in 3 and an additional 3 children had Sturge-Weber-Dimitri syndrome. There were no gross or microscopic abnormalities in 1 patient. This report provides the first comprehensive description of the pathologic findings in a series of children with refractory epilepsy of varying types treated by hemispherectomy-multilobar resection.

A review of cognitive outcome after hemidecortication in humans

This review of the effects of hemidecortication in humans has been limited to studies of cognitive outcome published during the last 20 years. More directly than in the case of split-brain patients, the patients reviewed here attest to the remarkable ability of a single hemisphere, whether left or right, to support at least at modest levels a wide range of cognitive functions--from visual perception, through memory and intellectual processes, to language and even speech. In some cases, as has been indicated, the surgical removal of a diseased hemisphere has resulted in improvement of cognitive function. This positive outcome has occurred more frequently in patients with early (i.e. congenital or perinatal) onset of seizure disorders than in those with late onset (e.g. Rasmussen's disease). But even for the latter patients, the cognitive costs of the surgery per se have rarely been severe. And in both types of case, the incidence of either complete or substantial postoperative relief from intractable seizures has been high, ranging around 80-90%. Although the therapeutic efficacy and small cognitive costs of the surgery are now quite well established, little is known yet regarding the specific cognitive defects that arise from the loss of one as opposed to the other cerebral hemisphere. Intelligence levels have been found to be equally low, averaging in the mid-60s and almost never rising above 100 in patients with either left or right hemidecortications, and memory quotients have most often appeared to fall in line with the IQ scores, again without clear evidence of any difference in the effects of left and right removals. Even in the case of visual spatial perception, considered to be a hallmark of right hemisphere function, the evidence is unclear, one study reporting selective impairment on difficult visuospatial tasks in right hemispherectomised patients, but another not. Only in regard to language processes is there a consensus regarding the differential effects of left and right hemidecortication, and here the differences are apparent only in the relatively subtler aspects of language. Thus, the isolated right hemisphere is at a significant disadvantage compared with the left in the comprehension of abstract, low frequency words, in phonetic feature analysis, and in the subtleties of grammar, such as the comprehension of passive negative constructions and the correct use of morphological markers in unfamiliar contexts (e.g. application of comparative and superlative forms of an adjective to nonwords.(ABSTRACT TRUNCATED AT 400 WORDS)

The place of hemispherectomy and major cortical resection in the control of drug resistant epilepsy

The results of hemispherectomy are very satisfactory but depend upon the technique used. Recent reports from a number of centres confirm that 73% of patients are fit free following hemispherectomy. Delayed pressure complications of hemispherectomy are discussed, together with the modified techniques required to cope with such problems.