Hemispheric disconnection: callosotomy and hemispherotomy

Functional hemispheric disconnection procedures for chronic epilepsy: history, indications, techniques, complications and current practice in Europe. A consensus statement on behalf of the EANS functional neurosurgery section

Introduction

The surgical procedure for severe, drug-resistant, unilateral hemispheric epilepsy is challenging. Over the last decades the surgical landscape for hemispheric disconnection procedures changed from anatomical hemispherectomy to functional hemispherotomy with a reduction of complications and stable good seizure outcome. Here, a task force of European epilepsy surgeons prepared, on behalf of the EANS Section for Functional Neurosurgery, a consensus statement on different aspects of the hemispheric disconnection procedure.

Research question

To determine history, indication, timing, techniques, complications and current practice in Europe for hemispheric disconnection procedures in drug-resistant epilepsy.

Material and methods

Relevant literature on the topic was collected by a literature search based on the PRISMA 2020 guidelines.

Results

A comprehensive overview on the historical development of hemispheric disconnection procedures for epilepsy is presented, while discussing indications, timing, surgical techniques and complications. Current practice for this procedure in European epilepsy surgery centers is provided. At present, our knowledge of long-term seizure outcomes primarily stems from open surgical disconnection procedures. Although minimal invasive surgical techniques in epilepsy are rapidly developing and reported in case reports or small case series, long-term seizure outcome remain uncertain and needs to be reported.

Discussion and conclusion

This is the first paper presenting a European consensus statement regarding history, indications, techniques and complications of hemispheric disconnection procedures for different causes of chronic, drug-resistant epilepsy. Furthermore, it serves as the pioneering document to report a comprehensive overview of the current surgical practices regarding this type of surgery employed in renowned epilepsy surgery centers across Europe.

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.

Transtemporal approach to hypothalamic hamartomas in children: report of 3 cases

The surgical approach to hypothalamic hamartomas (HHs) associated with medically refractory epilepsy is challenging because of these lesions' deep midline or paramedian location. Whether the aim is resection or disconnection, the surgical corridor dictates how complete a procedure can be achieved. Here, the authors report a transtemporal approach suitable for Delalande type I, inferior extraventricular component of type III, and type IV lesions. This approach provides optimal visualization of the plane between the hamartoma and the hypothalamus with no manipulation to the pituitary stalk and brainstem, allowing for extensive disconnection while minimizing injury to adjacent neurovascular structures.Through a 1-cm corticectomy in the middle temporal gyrus, a surgical tract is developed under neuronavigational guidance toward the plane of intended disconnection. On reaching the mesial temporal pia-arachnoid margin, it is opened, providing direct visualization of the hamartoma, which is then disconnected or resected as indicated. Critical neurovascular structures are generally not exposed through this approach and are preserved if encountered.Three patients (mean age 4.9 years) with intractable epilepsy were treated using this technique as part of the national Children's Epilepsy Surgery Service. Following resection, the patient in case 1 (Delalande type I) is seizure free off medication at 3 years' follow-up (Engel class IA). The patient in case 2 (Delalande type III) initially underwent partial disconnection through a transcallosal interforniceal approach and at first had significant seizure improvement before the seizures worsened in frequency and type. Complete disconnection of the residual lesion was achieved using the transtemporal approach, rendering this patient seizure free off medication at 14 months postsurgery (Engel class IA). The patient in case 3 (Delalande type IV) underwent incomplete disconnection with a substantial reduction in seizure frequency at 3 years' follow-up (Engel class IIIC). There were no surgical complications in any of the cases.The transtemporal approach is a safe and effective alternative to more conventional surgical approaches in managing HHs with intractable epilepsy.

Tailored multilobar disconnective epilepsy surgery in the posterior quadrant

OBJECTIVE

Surgical treatment of drug-resistant epilepsy originating from the posterior quadrant (PQ) of the brain often requires large multilobar resections, and disconnective techniques have been advocated to limit the risks associated with extensive tissue removal. Few previous studies have described a tailored temporoparietooccipital (TPO) disconnective approach; only small series with short postoperative follow-ups have been reported. The aim of the present study was to present a tailored approach to multilobar PQ disconnections (MPQDs) for epilepsy and to provide details about selection of patients, presurgical investigations, surgical technique, treatment safety profile, and seizure and cognitive outcome in a large, single-center series of patients with a long-term follow-up.

METHODS

In this retrospective longitudinal study, the authors searched their prospectively collected database for patients who underwent MPQD for drug-resistant epilepsy in the period of 2005-2017. Tailored MPQDs were a posteriori grouped as follows: type I (classic full TPO disconnection), type II (partial TPO disconnection), type III (full temporooccipital [TO] disconnection), and type IV (partial TO disconnection), according to the disconnection plane in the occipitoparietal area. A bivariate statistical analysis was carried out to identify possible predictors of seizure outcome (Engel class I vs classes II-IV) among several presurgical, surgical, and postsurgical variables. Preoperative and postoperative cognitive profiles were also collected and evaluated.

RESULTS

Forty-two consecutive patients (29 males, 24 children) met the inclusion criteria. According to the presurgical evaluation (including stereo-electroencephalography in 13 cases), 12 (28.6%), 24 (57.1%), 2 (4.8%), and 4 (9.5%) patients received a type I, II, III, or IV MPQD, respectively. After a mean follow-up of 80.6 months, 76.2% patients were in Engel class I at last contact; at 6 months and 2 and 5 years postoperatively, Engel class I was recorded in 80.9%, 74.5%, and 73.5% of cases, respectively. Factors significantly associated with seizure freedom were the occipital pattern of seizure semiology and the absence of bilateral interictal epileptiform abnormalities at the EEG (p = 0.02). Severe complications occurred in 4.8% of the patients. The available neuropsychological data revealed postsurgical improvement in verbal domains, whereas nonunivocal outcomes were recorded in the other functions.

CONCLUSIONS

The presented data indicate that the use of careful anatomo-electro-clinical criteria in the presurgical evaluation allows for customizing the extent of surgical disconnections in PQ epilepsies, with excellent results on seizures and an acceptable safety profile.

Longitudinal brain functional and structural connectivity changes after hemispherotomy in two pediatric patients with drug-resistant epilepsy

The main focus of the present study was to explore the longitudinal changes in the brain executive control system and default mode network after hemispherotomy. Resting-state functional magnetic resonance imaging and diffusion tensor imaging were collected in two children with drug-resistnt epilepsy underwent hemispherotomy. Two patients with different curative effects showed different trajectories of brain connectivity after surgery. The failed hemispherotomy might be due to the fact that the synchrony of epileptic neurons in both hemispheres is preserved by residual neural pathways. Loss of interhemispheric correlations with increased intrahemispheric correlations can be considered as neural marker for evaluating the success of hemispherotomy.

The Wada test might predict postoperative fine finger motor deficit after hemispherotomy

INTRODUCTION

Cerebral hemispherotomy is a surgical method with a high rate of seizure reduction in patients with intractable epilepsy. However, there is a probability of postoperative motor deficits. The objective of this study was to investigate whether the Wada test can help predict motor function outcomes after hemispherotomy and, therefore, may be useful in decision-making and patient selection.

PATIENTS AND METHOD

A total of 13 patients with hemispherical intractable epilepsy underwent hemispherical disconnection surgeries. Six of them underwent the Wada test to evaluate motor function and language function followed by peri-insula hemispherotomy. The patients' age ranged from 11 to 45years (mean 27years).

RESULTS

Three of six patients had reduced dexterity on the Wada test. The finger motor function in the other patients did not change on the Wada test. Postoperatively, all patients who had decreased fine motor movement on the Wada test showed postoperative clumsiness of their hands and fingers.

CONCLUSIONS

The Wada test might predict postoperative fine finger motor deficit after hemispherotomy. This study showed that gross motor function was compensated in the ipsilateral hemisphere, whereas fine finger motor movement function remained in the contralateral frontal cortex.

The start and development of epilepsy surgery in Europe: a historical review

Epilepsy has not always been considered a brain disease, but was believed to be a demonic possession in the past. Therefore, trepanation was done not only for medical but also for religious or spiritual reasons, originating in the Neolithic period (3000 BC). The earliest documentation of trepanation for epilepsy is found in the writings of the Hippocratic Corpus and consisted mainly of just skull surgery. The transition from skull surgery to brain surgery took place in the middle of the nineteenth century when the insight of epilepsy as a cortical disorder of the brain emerged. This led to the start of modern epilepsy surgery. The pioneer countries in which epilepsy surgery was performed in Europe were the UK, Germany, and The Netherlands. Neurosurgical forerunners like Sir Victor Horsley, William Macewen, Fedor Krause, and Otfrid Foerster started with "modern" epilepsy surgery. Initially, epilepsy surgery was mainly done with the purpose to resect traumatic lesions or large surface tumours. In the course of the twentieth century, this changed to highly specialized microscopic navigation-guided surgery to resect lesional and non-lesional epileptogenic cortex. The development of epilepsy surgery in Southern Europe, which has not been described until now, will be elaborated in this manuscript. To summarize, in this paper, we provide (1) a detailed description of the evolution of European epilepsy surgery with special emphasis on the pioneer countries; (2) novel, never published information about the development of epilepsy surgery in Southern Europe; and (3) we review the historical dichotomy of invasive electrode implantation strategy (Anglo-Saxon surface electrodes versus French-Italian stereoencephalography (SEEG) model).

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.

Pediatric functional hemispherectomy: outcome in 92 patients

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Hemispherotomy: efficacy and analysis of seizure recurrence

OBJECT

Hemispherotomy generally is performed in hemiparetic patients with severe, intractable epilepsy arising from one cerebral hemisphere. In this study, the authors evaluate the efficacy of hemispherotomy and present an analysis of the factors influencing seizure recurrence following the operation.

METHODS

The authors performed a retrospective review of 49 patients (ages 0.2-20.5 years) who underwent functional hemispherotomy at their institution. The first 14 cases were traditional functional hemispherotomies, and included temporal lobectomy, while the latter 35 were performed using a modified periinsular technique that the authors adopted in 2003.

RESULTS

Thirty-eight of the 49 patients (77.6%) were seizure free at the termination of the study (mean follow-up 28.6 months). Of the 11 patients who were not seizure free, all had significant improvement in seizure frequency, with 6 patients (12.2%) achieving Engel Class II outcome and 5 patients (10.2%) achieving Engel Class III. There were no cases of Engel Class IV outcome. The effect of hemispherotomy was durable over time with no significant change in Engel class over the postoperative follow-up period. There was no statistical difference in outcome between surgery types. Analysis of factors contributing to seizure recurrence after hemispherotomy revealed no statistically significant predictors of treatment failure, although bilateral electrographic abnormalities on the preoperative electroencephalogram demonstrated a trend toward a worse outcome.

CONCLUSIONS

In the present study, hemispherotomy resulted in freedom from seizures in nearly 78% of patients; worthwhile improvement was demonstrated in all patients. The seizure reduction observed after hemispherotomy was durable over time, with only rare late failure. Bilateral electrographic abnormalities may be predictive of posthemispherotomy recurrent seizures.

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

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

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.

[Corticectomy: technical considerations]

The surgical treatment of epilepsy requires careful preparation and presents a certain number of technical specificities. The neurosurgeon must master not only the technical aspects but also the therapeutic and functional trade-off in order to modulate the procedure according to morphological and electrophysiological intraoperative data. A large number of technical variants have been developed to correspond to epileptological or functional anatomical considerations. Until this point, the choice of a particular technique does not seem to have a significant impact on the therapeutic effectiveness of surgery, and differences in results can be related to the presurgical evaluation and surgical indications. On the other hand, technical development promises to play an important role in limiting the long-term neurocognitive consequences of surgery.

Operative technique: the anterior transcallosal transseptal interforniceal approach to the third ventricle and resection of hypothalamic hamartomas

Background. We have previously described the resection of hypothalamic hamartomas (HH) using a transcallosal approach [Transcallosal resection of hypothalamic hamartomas, with control of seizures, in children with gelastic epilepsy, Neurosurgery, 2001]. Since then, we have refined the technique and now describe in detail an anterior transcallosal transseptal interforniceal approach to the third ventricle as a variation of the standard transcallosal interforniceal approach. The results of this series are presented to demonstrate the safety and efficacy of this approach. Method. HH were resected via an anterior transcallosal, transseptal, interforniceal approach to the third ventricle. This is a more anterior approach to the third ventricle with a more acute trajectory than has been described previously. Results. This approach provided excellent access to the floor of the third ventricle with minimal forniceal retraction and avoidance of dissection of the deep venous structures. Transcallosal resection of HH was performed in 45 patients aged 2.9-33 years (mean 11.3 years). Morbidity was minimal, including transient hemiparesis in 3, ongoing diabetes insipidus in 2, early short-term memory impairment in 16 (persistent in 6) and one patient developed pneumonia postoperatively but recovered. Conclusion. The anterior transcallosal transseptal interforniceal technique is an effective and relatively safe technique when used for the resection of HH. This operative approach is applicable to other pathology in the third ventricle or hypothalamic region and has advantages compared with the standard transcallosal approach to the third ventricle.

Early hemispherectomy in catastrophic epilepsy

The authors report their experience about a neuro-cognitive and epileptic long-term follow-up of children with catastrophic epilepsy treated with hemispherectomy in the first 5 years of life. Nineteen children with resistant epilepsy that significantly interfered with their neuro-cognitive development underwent hemispherectomy within 5 years of life (mean: 2 years, 3 months; range: 5 months to 5 years). All patients were assessed before surgery and after, at least at the end of the follow-up (mean: 6 years and 6 months; range: 2-11 years and 2 months) with a full clinical examination including motor ability and functional status evaluation as well as behaviour observation, neuroimaging and an ictal/interictal prolonged scalp video-EEG. A seizure-free outcome was obtained in 73.7% of patients. Gross motility generally improved and cognitive competence did not worsen, with an evident progress in two cases. Consistently with previous reports, evolution was worse in cortical dysplasia than in progressive or acquired vascular cerebropathies. The excellent epileptic outcome and the lack of developmental deterioration in comparison with other more aged series seem to suggest a possible better evolution in earlier surgery treatment. To confirm this suggestion, however, further experience with larger series is needed.

Surgical management of hypothalamic hamartomas with epilepsy: the stereoendoscopic approach

OBJECTIVE

Hypothalamic hamartomas (HHs) require surgical treatment in patients presenting with refractory epilepsy.

METHODS

The authors report on a single-center series of 33 patients (24 males, 9 females) who underwent surgery between January 1997 and April 2004. They experienced several types of seizure (gelastic, tonic, partial, atonic, generalized tonic-clonic, dacrystic, infantile spasm, mental retardation, and behavioral and endocrinological abnormalities). Forty-nine interventions were carried out. Every patient, with the exception of the first, underwent hamartoma disconnection (pterional approach, six patients; endoscopy, 15 patients; both, 11 patients). The endoscopic approach was carried out with a frameless stereotactic system to enhance feasibility and efficacy of the disconnecting procedure.

RESULTS

Surgery-related neurological complications occurred in two patients, both after a pterional microsurgical approach. Furthermore, two patients experienced panhypopituitarism and one patient experienced transitory central insipid diabetes. All patients but one showed recovery or considerable improvement of their epilepsy (Engel Class 1, 48.5%; Engel Class 2, 3%; Engel Class 3, 45.5%; mean follow-up duration, 1 yr 7 mo).

CONCLUSION

According to the proposed classification of sessile HH into four types, the best candidates for endoscopic disconnection are Type 2 and Type 3 HHs. In the present series, 90% of patients affected by Type 2 HH became seizure free and the remaining 10% improved; of those with Type 3 HH at presentation, 35.3% recovered and 60% improved. Neuropsychological and endocrinological test results showed improvement in many patients. Data from our series demonstrate that frameless stereotactic endoscopic disconnection should be considered as the treatment of choice in the presence of favorable anatomic conditions.

Transventricular hemispherotomy for surgical treatment of intractable epilepsy

Surgical procedures for cerebral hemispherotomy may be broadly divided into those using a lateral and those using a vertical approach. However, careful study of surgical procedures using the lateral approach described in the literature shows differences in the approach to the ventricles. We discuss the application of transventricular hemispherotomy as a technique which provides relatively easy ventricular access for cerebral hemispherotomy. Transventricular hemispherotomy was successfully performed in a 36-year-old woman who was diagnosed with intractable epilepsy due to Sturge-Weber disease, and in a 25-year-old man who had developed intractable post-traumatic seizures after suffering cerebral contusion in a traffic accident as a child. These patients had no seizures or complications after surgery, and both patients have been weaned from antiepileptic drugs. The transventricular approach, as compared with other lateral approaches described in the literature, provides easy access to the ventricular cavity. Transventricular hemispherotomy proved to be a useful approach that allowed the following four common steps in cerebral hemispherotomy to be performed safely: (i) interruption of the internal capsule and corona radiata; (ii) resection of the medial temporal structures; (iii) transventricular corpus callosotomy; and (iv) disruption of the frontal horizontal fibers.

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.

Transsylvian functional hemispherectomy

OBJECTIVE

To describe the technique of transsylvian-transventricular functional hemispherectomy developed at our institution.

METHODS

We review appropriate patient selection and evaluation, timing of surgery, selection of surgical approach, preoperative preparation, details of operative procedure, and postoperative management.

CONCLUSIONS

The transsylvian "keyhole" functional hemispherectomy technique involves a smaller craniotomy than other functional hemispherectomy techniques and consists of transsylvian exposure, resection of mesial temporal structures, transventricular frontobasal disconnection, callosotomy, and occipitoparietal disconnection. The key advantages of this approach compared to the Rasmussen's "classic" functional hemispherectomy are smaller exposure, shorter operative time, and lower blood loss. The efficacy of functional hemispherectomy procedures in achieving seizure freedom appears to be at least as good compared to resective procedures. The long-term complication rate will require longer follow-up times.

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.

Surgical removal of corpus callosum infiltrated by low-grade glioma: functional outcome and oncological considerations

Object. Although still controversial, many authors currently advocate extensive resection in the treatment of low-grade gliomas (LGGs). Because these tumors usually migrate along white matter pathways, the corpus callosum is often invaded. Nevertheless, there is evidently no specific study featuring resection of the corpus callosum infiltrated by glioma, despite abundant literature concerning callosotomy in epilepsy surgery or transcallosal ventricular approaches. The aim of this paper was to analyze functional outcome following removal of corpus callosum invaded by LGG and to analyze the impact of this callosectomy on the quality of resection.

Methods. Between 1996 and 2002, a total of 32 patients harboring an LGG involving part of the corpus callosum and having no or only a mild preoperative deficit underwent surgery aided by intraoperative electrical mapping to preserve eloquent structures identified on stimulation and to perform the most extensive resection possible.

Preoperatively, no clinical response was elicited on stimulation of the corpus callosum; thus, the part of this structure that was invaded by LGG was removed. Despite immediate postoperative neurological worsening, all patients but one recovered within 3 months and returned to a normal socioprofessional life. The additional callosectomy allowed for nine total resections, 18 subtotal resections, and five partial resections. Furthermore, only two cases of contralateral hemispherical migration occurred during a median follow up of 3 years.

Conclusions. Resection of the corpus callosum infiltrated by glioma improves the quality of tumor removal without increasing the risk of sequelae.

Transcortical or transcallosal approach to ventricle-associated lesions: a clinical study on the prognostic role of surgical approach

Most entities in and around the anterior two-thirds of the supratentorial ventricles can be reached via transcortical or transcallosal approach. This study examined the effect of surgical approach on the postoperative neurological outcome. Thirty-eight patients with intra- and periventricular supratentorial lesions were operated on by either frontal transcortical or anterior transcallosal approach. Postoperative diencephalic damage occurred in 22% of patients in the transcortical group and in 36% in the transcallosal group; transient mutism was virtually equivalent in the two groups. Postoperative epilepsy (26%) and subdural fluid collections (30%) occurred only in the transcortical group. The incidence of postoperative hemiparesis was higher in the transcallosal group. There was a high correlation between postoperative Glasgow Outcome Score of 5 and preoperative severity of neurological disease but no correlation between postoperative Glasgow Outcome Score of 5 and location of the lesion or between postoperative clinical course and surgical approach. Surgical outcome of ventricle-associated lesions depends mainly on the severity of preoperative symptoms and not on surgical approach. Additionally, the incidence of postoperative seizures and subdural fluid collections after transcortical surgery is high.

Disconnecting surgical treatment of hypothalamic hamartoma in children and adults with refractory epilepsy and proposal of a new classification

A series of 17 patients aged from 9 months to 32 years with refractory epilepsy due to hypothalamic hamartoma were treated by total removal (one case) and disconnection (16 cases) between 1997 and 2002. The mean age at seizure onset was 16 months. Sixteen patients had gelastic seizures, 14 had partial seizures and three had generalized tonic-clonic seizures. The mean seizure frequency was 21 per day. Four patients had borderline intelligence quotient and the others were mentally retarded. Five patients presented with precocious puberty, one with acromegaly, and four suffered from obesity. Brain magnetic resonance imaging, performed at least twice in each patient, showed the hamartoma as a stable homogeneous interpeduncular mass implanted either on the mammilary tubercle or on the wall of the third ventricle with variable extension to the bottom. Ictal single photon emission computed tomography, performed in four patients, showed hyperperfusion within the hamartoma in two patients. Twenty-five operations were performed in the 17 patients. The first patient underwent total removal of the hamartoma, whereas the following 16 patients underwent disconnection through open surgery (14 procedures) and/or endoscopy (9 procedures). Eight patients became seizure-free, one patient had only brief gelastic seizures, and eight patients were dramatically improved with a mean follow up of 18.6 months (8 days to 43 months). Surgery was safe in all but two patients: the first patient had transient hemiplegia and the third cranial nerve paresis, and the other developed hemiplegia due to ischemia of the middle cerebral artery territory. The quality of life, and behavior and school performance were greatly improved in most patients. Our series illustrates the feasibility and relative safety of disconnection surgery for hypothalamic hamartomas with seizure relief in 53% of patients and dramatic improvement in the others. Surgical observations led us to propose a new anatomical classification according to the anatomical relationship between the hamartoma and the adjacent hypothalamus and third ventricle. Endoscopic disconnection seems to be a very safe way to treat hamartomas in intraventricular locations.

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.