Surgical treatment of intractable epilepsy accompanying cortical dysplasia

The relationship between morphological lesion, magnetic source imaging, and intracranial stereo-electroencephalography in focal cortical dysplasia

Magnetoencephalography (MEG) is a useful non-invasive technique for presurgical evaluation of focal cortical dysplasia patients. We aimed at clarifying the precise spatial relationship between the spiking volume determined with MEG, the seizure onset zone and the lesional volume in patients with focal cortical dysplasia.

We studied the spatial relationships between the MEG spiking volume determined with a recent analysis pipeline, the seizure-onset zone location determined with a quantitative index calculated from intracranial EEG signals (‘Epileptogenicity Index’) and the lesional volume delineated on brain MRI in 11 patients with Focal Cortical Dysplasia explored with Stereo-electroencephalography (SEEG).

A significant correlation between the MEG spiking activity and the Epileptogenicity Index was found in 8/11 patients. 7/8 patients were operated upon and had good surgical outcome. For three patients, no correlation between Epileptogenicity Index and spiking activity was observed; only one of those three patients had good surgical outcome.

The lesion was at least partially overlapping with the seizure-onset zone in 8/9 patients with a lesion clearly identifiable by MRI. However, 57% of the SEEG epileptogenic contacts were located outside of the lesional volume. Lastly 44% of the highly epileptogenic SEEG contacts were located within the spiking volume and 22% of them were located exclusively in the spiking volume and not in the lesion. For 7/9 patients with a lesion, < 50% of epileptogenic SEEG contacts were included within the lesion: for 5/7 patients MEG provided an added value for targeting the epileptogenic region through intracranial electrodes, while for two of seven patients MEG detected only a few extralesional epileptogenic contacts.

Our study suggests that modeling of the spiking volume with MEG is a promising tool to localize non-invasively the seizure-onset zone in patients with focal cortical dysplasia. Combined with brain MRI, MEG modeling of the spiking volume contributes to delineate the spatial extent of the seizure-onset zone.

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This study investigates the relationship between the seizure focus, the lesion and the MEG spikes in Focal Cortical Dysplasia (FCD).

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The lesion, the seizure-onset zone and the MEG spiking volumes in FCD patients are largely co-extensive brain regions.

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MEG is helpful to disclose epileptogenic areas remote from the lesion.

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MEG is complementary to MRI to estimate the full extent of the SOZ in patients with FCD.

Six adult patients with septo-optic dysplasia and drug-resistant epilepsy: Clinical findings and course

Septo-optic dysplasia (SOD) is a rare disorder associated with optic nerve hypoplasia, pituitary abnormalities and agenesis/dysgenesis of midline brain structures including the septum pellucidum and corpus callosum. Though sometimes associated with drug-resistant epilepsy, this association has not been well studied. We report six SOD patients with associated malformation of cortical development (MCD) and drug-resistant epilepsy who underwent video-EEG telemetry at our centre between 1998 and 2016 for drug-resistant epilepsy. ‬Three then underwent surgery; right temporal neocortical resection, right functional hemispherectomy and placement of a vagus nerve stimulator. Clinical findings and the patients' ultimate courses are discussed.

3-T intraoperative MRI (iMRI) for pediatric epilepsy surgery

PURPOSE

Three-tesla intraoperative MRI (iMRI) is a promising tool that could help confirm complete resections and disconnections in pediatric epilepsy surgery, leading to improved outcomes. However, a large proportion of epileptogenic pathologies in children are poorly defined on imaging, which brings into question the utility of iMRI for these cases. Our aim was to compare postoperative seizure outcomes between iMRI- and non-iMRI-based epilepsy surgeries.

METHODS

We performed a comparative retrospective analysis of non-iMRI- versus iMRI-based epilepsy surgeries with 2-year follow-up. Patients were stratified into well-defined cases (WDCs), poorly defined cases (PDCs), and diffuse hemispheric cases (DHCs). Primary outcomes were rates of complete seizure freedom and surgical complications. Secondary outcomes included good (Engel class I/II) seizure outcome, extent of resection/disconnection, and operative duration. Regression models were used to adjust for confounding.

RESULTS

Thirty-nine iMRI-based and 39 non-iMRI-based surgeries were included. The distributions of age, sex, and lesion class in each era were similar, but the distributions of individual pathologies varied. Seizure freedom and complication rates at 2-year follow-up were not different between the groups, but Engel class I/II outcome was more common in the iMRI group. Extent of resection/disconnection and length of surgery were similar in both groups. PDCs had the worst outcomes, which were unchanged by the use of iMRI.

CONCLUSION

Three-tesla iMRI-based epilepsy surgery may have the potential to improve patient outcomes. However, we conclude that iMRI, in its current state of use at our institute, does not improve outcomes for children undergoing epilepsy surgery. Given that its use appears safe, further research on this technology is warranted, particularly for the most challenging PDCs.

Outcome after epilepsy surgery for cortical dysplasia in children

BACKGROUND AND PURPOSE

Epilepsy surgery for medically refractory epilepsy secondary to cortical dysplasia in children poses special challenges. We aim to review the current available literature on the outcome after epilepsy surgery for cortical dysplasia in children and critically evaluate the prognostic predictors of outcome.

METHODS

A comprehensive review of the literature was performed focusing on the outcome after epilepsy surgery for cortical dysplasia in children. Two large recent meta-analyses that included children and adults and several pediatric series of cortical dysplasia in children were reviewed.

RESULTS AND CONCLUSIONS

The overall seizure freedom rates range from 40 to 73 %, at about 2 years after surgery; most studies report 50-55% success rate. Complete resection of the epileptogenic lesion/zone remains the most important variable predictive of postoperative seizure freedom. Features unique to cortical dysplasia that limits our ability to ensure complete resection of the epileptogenic zone are reviewed.

Cognitive and epilepsy outcomes after epilepsy surgery caused by focal cortical dysplasia in children: early intervention maybe better

BACKGROUND

Focal cortical dysplasia (FCD) is a specific malformation of cortical development harboring intrinsic epileptogenicity, and most of the patients develop drug-resistant epilepsy in early childhood. The detrimental effects of early and frequent seizures on cognitive function in children are significant clinical issues. In this study, we evaluate the effects of early surgical intervention of FCD on epilepsy outcome and cognitive development.

METHODS

From 2006 to 2013, 30 children younger than 18 years old underwent resective surgery for FCDs at Taipei Veterans General Hospital. The mean age at surgery was 10.0 years (range 1.7 to 17.6 years). There were 21 boys and 9 girls. In this retrospective clinical study, seizure outcome, cognitive function, and quality of life were evaluated. To evaluate the effects to outcomes on early interventions, the patients were categorized into four groups according to age of seizure onset, duration of seizure before surgery, and severity of cognitive deficits.

RESULTS

Eleven of 22 (50 %) patients demonstrated developmental delay preoperatively. The Engel seizure outcome achievements were class I in 21 (70 %), class II in 2 (7 %), class III in 6 (20 %), and class IV in 1 (3 %) patients. The locations of FCDs resected were in the frontal lobe in 18 cases, temporal lobe in 7, parietal lobe in 2, and in bilobes including frontoparietal lobe in 2 and parieto-occipital lobes in 1. Eight cases that had FCDs involved in the rolandic cortex presented hemiparesis before surgical resection. Motor function in four of them improved after operation. The histopathological types of FCDs were type Ia in 1, type Ib in 7, type IIa in 7, type IIb in 12, and type III in 3 patients. FCDs were completely resected in 20 patients. Eighteen (90 %) of them were seizure free (p < 0.001) with three patients that received more than one surgery to accomplish complete resection. The patients who had early seizure onset, no significant cognitive function deficit, and early surgical intervention with complete resection in less than 2 years of seizure duration showed best outcomes on seizure control, cognitive function, and quality of life.

CONCLUSION

Delay in cognitive development and poor quality of life is common in children treated for FCDs. Early surgical intervention and complete resection of the lesion help for a better seizure control, cognitive function development, and quality of life. FCDs involved eloquent cortex may not prohibit complete resection for better outcomes.

Emerging surgical strategies of intractable frontal lobe epilepsy with cortical dysplasia in terms of extent of resection

Objective

Cortical dysplasia (CD) is one of the common causes of epilepsy surgery. However, surgical outcome still remains poor, especially with frontal lobe epilepsy (FLE), despite the advancement of neuroimaging techniques and expansion of surgical indications. The aim of this study was to focus on surgical strategies in terms of extent of resection to improve surgical outcome in the cases of FLE with CD.

Methods

A total of 11 patients of FLE were selected among 67 patients who were proven pathologically as CD, out of a total of 726 epilepsy surgery series since 1992. This study categorized surgical groups into three according to the extent of resection : 1) focal corticectomy, 2) regional corticectomy, and 3) partial functional lobectomy, based on the preoperative evaluation, in particular, ictal scalp EEG onset and/or intracranial recordings, and the lesions in high-resolution MRI. Surgical outcome was assessed following Engel's classification system.

Results

Focal corticectomy was performed in 5 patients and regional corticectomy in another set of 5 patients. Only 1 patient underwent partial functional lobectomy. Types I and II CD were detected with the same frequency (45.45% each) and postoperative outcome was fully satisfactory (91%).

Conclusion

The strategy of epilepsy surgery is to focus on the different characteristics of each individual, considering the extent of real resection, which is based on the focal ictal onset consistent with neuroimaging, especially in the practical point of view of neurosurgery.

A meta-analysis of predictors of seizure freedom in the surgical management of focal cortical dysplasia

Object

Focal cortical dysplasia (FCD) is one of the most common causes of medically refractory epilepsy leading to surgery. However, seizure control outcomes reported in isolated surgical series are highly variable. As a result, it is not clear which variables are most crucial in predicting seizure freedom following surgery for FCD. The authors' aim was to determine the prognostic factors for seizure control in FCD by performing a meta-analysis of the published literature.

Methods

A MEDLINE search of the published literature yielded 37 studies that met inclusion and exclusion criteria. Seven potential prognostic variables were determined from these studies and were dichotomized for analysis. For each variable, individual studies were weighted by inverse variance and combined to generate an odds ratio favoring seizure freedom. The methods complied with a standardized meta-analysis reporting protocol.

Results

Two thousand fourteen patients were included in the analysis. The overall rate of seizure freedom (Engel Class I) among patients undergoing surgery for FCD in the cohort of studies was 55.8% ± 16.2%. Partial seizures, a temporal location, detection with MRI, and a Type II Palmini histological classification were associated with higher rates of postoperative seizure control. As a treatment-related factor, complete resection of the anatomical or electrographic abnormality was the most important predictor overall of seizure freedom. Neither age nor electroencephalographic localization of the ictal onset significantly affected seizure freedom after surgery.

Conclusions

Using a large population cohort pooled from the published literature, an analysis identified important factors that are prognostic in patients with epilepsy due to FCD. The most important of these factors—diagnostic imaging and resection—provide modalities through which improvements in the impact of FCD can be effected.

Focal cortical dysplasia. Clinical-radiological-pathological associations

INTRODUCTION

The term focal cortical dysplasia (FCD) describes a particular migration disorder with a symptomatology mainly characterised by drug-resistant epileptic seizures, typical neuroradiological images, and histological characteristics, as well as a very positive response to surgical treatment in the majority of cases.

MATERIAL AND METHODS

A total of 7 patients were studied, comprising 6 children with a mean age of 34.3 months and one 25-year-old male with very persistent focal seizures and MRI images that showed FCD.

RESULTS

Three of the patients (all girls) were operated on while very young, with extirpation of the FCD and the surrounding area; with the histopathology study showed agreement between the MRI images and the macroscopic study of the slices. The histology study showed findings typical of a Taylor-type FCD (poor differentiation between the cortical grey matter and the subcortical white matter, and balloon cells). Three years after the FCD extirpation, the same 3 patients remained seizure-free with no anti-epilepsy medication. Two others have seizure control with medication, another (the adult) is on the surgical waiting list, and the remaining patient refused the operation.

CONCLUSION

Taylor-type FCD is associated with a high percentage of all drug-resistant focal seizures, and it needs to be identified and extirpated as soon as possible. Well planned and well-performed surgery that leaves no remains of dysplasia can cure the disease it in many cases.

Altered firing rates and patterns in interneurons in experimental cortical dysplasia

Cortical dysplasia (CD) is associated with severe epilepsy in humans, and the in utero irradiation of fetal rats provides a model of this disorder. These animals show a selective loss of inhibitory interneurons, and the surviving interneurons have a reduced excitatory synaptic drive. The current study was undertaken to see how alterations in synaptic input would affect spontaneous firing of interneurons in dysplastic cortex. We recorded spontaneous action potentials and excitatory and inhibitory postsynaptic currents (EPSCs and IPSCs, respectively) from somatostatin (SST)-, parvalbumin (PV)-, and calretinin (CR)-immunoreactive (ir) interneurons. We found that SST- and PV-ir interneurons fired less frequently and with less regularity than controls. This corresponded to a relative imbalance in the ratio of EPSCs to IPSCs that favored inhibition. In contrast, CR-ir interneurons from CD showed no differences from controls in spontaneous firing or ratio of EPSCs to IPSCs. Additional studies demonstrated that synaptic input had a powerful effect on spontaneous firing in all interneurons. These findings demonstrate that a relative reduction in excitatory drive results in less active SST- and PV-ir interneurons in irradiated rats. This would further impair cortical inhibition in these animals and may be an important mechanism of epileptogenesis.

Surgical outcome for focal cortical dysplasia: an analysis of recent surgical series

OBJECT

Focal cortical dysplasia (FCD) is an important cause of intractable epilepsy and is at times treatable by resection. The now widespread use of MR imaging and recent advancement of functional imaging have increased the number of patients undergoing surgical treatment for FCD. The objective of this review is to critically examine and to provide a summary of surgical series on FCD published since 2000.

METHODS

Studies concerning surgery for FCD were identified from MEDLINE and references of selected articles and book chapters. Data from these included studies were summarized and analyzed to identify factors correlated with seizure outcome.

RESULTS

Sixteen studies were identified, and 469 patients met our selection criteria. Seizure-free outcome at 1-year postoperatively was achieved in 59.7% of the patients. Children and adults were equally likely to benefit from the surgery. Complete resection (OR 13.7, 95% CI 6.68-28.1; p < 0.0001) and temporal location (OR 2.15, 95% CI 1.26-3.69; p = 0.0073) were two positive prognostic indicators of seizure-free outcome. Utilization of invasive monitoring did not affect the chance of seizure remission, but firm conclusions could not be drawn because patients were not randomized.

CONCLUSIONS

The advancement of modern imaging has transformed the process of surgical candidate selection for partial epilepsy due to FCD. Patients from recent surgical series were more homogeneous in their clinical presentations and might represent FCD as an independent pathological entity. This likely explained the improved surgical outcome for this group of patients. These reports also documented the increased utilization of functional imaging, but their efficacy needs to be verified with further studies.

Epilepsy surgery of posterior quadrant dysplasia in the first year of life: experience of a single centre with long term follow-up

Posterior quadrant dysplasia (PQD) is a rare variant of cortical dysplasia involving the posterior regions of a single hemisphere. It is always associated with early onset, refractory epilepsy often characterized by a "catastrophic" evolution. The experience on its surgical management during the first year of life is limited to sporadic, isolated cases. Between 2002 and 2005, four children less than one-year-old and affected by drug-resistant epilepsy associated with PQD were admitted to our Institution and underwent surgical treatment. One patient remained seizure-free during all the follow-up (Engel I). The remaining three children showed a recurrence of the seizures, requiring subsequent surgical procedures in two cases. In one case (Engel II), the seizure control has been obtained thanks to pharmacological treatment. The other two patients respectively had only a partial (Engel III) and a less relevant reduction of the number of seizures (Engel IV). Both the epileptic and the neuropsychological outcome of our series were significantly influenced by persistent contralateral interictal anomalies rather than by the timing of the surgical procedure. Unpredictable results should be expected in this kind of patients if there is the detection of contralateral independent epileptiform activities on the EEG at diagnosis. Parents and relatives should be aware of the results' variability, even though a reduction of seizures may be expected, enabling an easier handling of the child's condition.

Dysembryoplastic neuroepithelial tumors in pediatric patients

OBJECTIVE

Dysembryoplastic neuroepithelial tumors (DNTs) are benign cortical tumors that are frequently associated with the medically intractable focal epilepsy. In this study, the authors delineate the clinical characteristics of DNTs in children and evaluate the role of cortical dysplasia (CD) in the epileptogenicity to find out the optimum surgical strategy.

METHODS

A retrospective analysis was performed for clinical data of children with DNT, who underwent surgery between 1996 and 2006. The adopted surgical methods were uniform according to the tumor location and included intraoperative electrocorticography (ECoG)-guided resection. The prognostic factors were evaluated for the two prognostic group categorized by the seizure outcome at one year after surgery.

RESULTS

Of 22 patients, the overall seizure free rate was 90.9% and the other two patients belonged to Engel class II during the mean follow-up period of 44.1 months. There was no worsening of the seizure after one year of surgery. Associated CD was found in 18 cases (81.8%) and in the 80% (8 of 10 cases) of the additionally resected areas according to the electrophysiologic studies.

CONCLUSIONS

The CD associated with DNT appears to have its own epileptogenicity. Therefore, complete removal of the CD with tumor itself is important for patient outcome. A thorough surgical approach can be accomplished by comprehensive presurgical evaluations and extensive surgery with the aid of the intraoperative ECoG or intracranial recording.

Local and remote epileptogenicity in focal cortical dysplasias and neurodevelopmental tumours

During the pre-surgical evaluation of drug-resistant epilepsy, the assessment of the extent of the epileptogenic zone and its organization is a crucial objective. Indeed, the epileptogenic zone may be organized as a simple focal lesional site or as a more complex network (often referred to as the 'epileptogenic network') extending beyond the lesion. This distinction is particularly relevant in developmental lesions such as focal cortical dysplasias or dysembryoplastic neuroepithelial tumours and may determine both the surgical strategy and the prognosis. In this study, we have quantified the epileptogenic characteristic of brain structures explored by depth electrodes in 36 patients investigated by stereoelectroencephalography and suffering from focal drug-resistant epilepsy associated with focal cortical dysplasias or dysembryoplastic neuroepithelial tumours. This quantification was performed using the 'Epileptogenicity Index' method that accounts for both the propensity of a brain area to generate rapid discharges and the time for this area to get involved in the seizure. Epileptogenicity Index values range from 0 (no epileptogenicity) to 1 (maximal epileptogenicity). We determined Epileptogenicity Index from signals recorded in distinct brain structures including the lesional site. We studied the type of epileptogenic zone organization (focal versus network) and looked for a correlation with clinical data and post-surgical outcome. Mean Epileptogenicity Index in lesional regions was 0.87 (+/-0.25), and 0.29 (+/-0.30) in 'non-lesional' structures. The number of highly epileptogenic structures (defined by Epileptogenicity Index value >or=0.4) was 3.14 (+/-1.87) in the whole population. We found that 31% of patients had only one epileptogenic structure (N(EI>or=0.4) = 1), therefore disclosing a strictly focal epileptogenic zone organization while 25 patients had more than one epileptogenic region, disclosing a network (61%) or bilateral (8%) epileptogenic zone organization. We observed a trend for a difference in seizure outcome according to the type of epileptogenic zone organization. Indeed, 57% of patients with network organization and 87% with focal organization were seizure-free while none of those with bilateral organization became seizure-free. The determination of Epileptogenicity Index computed from electrophysiological signals recorded according to the stereoelectroencephalography technique is a novel tool. Results suggest that it can help in the delineation of the epileptogenic zone associated with brain lesions and that it could be used in the definition of the subsequent surgical resection.

Focal cortical dysplasia: long term seizure outcome after surgical treatment

BACKGROUND

Studies of long term outcome after epilepsy surgery for cortical malformations are rare. In this study, we report our experience with surgical treatment and year to year long term outcome for a subgroup of patients with focal cortical dysplasia (FCD).

METHODS

We retrospectively analysed the records of 49 patients (females n = 26; males n = 23; mean age 25 (11) years) with a mean duration of epilepsy of 18 years (range 1-45). Preoperative MRI, histological results based on the Palmini classification and clinical year to year follow-up according to the International League Against Epilepsy (ILAE) classification were available in all patients.

RESULTS

98% of patients had a lesion on preoperative MRI. In addition to lobectomy (n = 9) or lesionectomy (n = 40), 14 patients had multiple subpial transections of the eloquent cortex. The resected tissue was classified as FCD type II b in 41 cases with an extratemporal (88%) and FCD type II a in 8 cases with a temporal localisation (100%). After a mean follow-up of 8.1 (4.5) years, 37 patients (76%) were seizure free, a subgroup of 23 patients (47%) had been completely seizure free since surgery (ILAE class 1a) and 4 patients (8%) had only auras (ILAE class 2). Over a 10 year follow-up, the proportion of satisfactory outcomes decreased, mainly within the first 3 years. During long term follow-up, 48% stopped antiepileptic drug treatment, 34% received a driver's license and 57% found a job or training.

CONCLUSION

Surgical treatment of epilepsy with FCD is not only successful in the short term but also has a satisfying long term outcome which remains constant after 3 years of follow-up but is not associated with better employment status or improvement in daily living.

Activation of mammalian target of rapamycin in cytomegalic neurons of human cortical dysplasia

OBJECTIVE

The cortex of patients with cortical dysplasia contains several abnormal cell types. Among the dysplastic cells, cytomegalic neurons are known to be electrically hyperactive and may contribute to epileptic activity. In this study, we sought to identify molecular markers of cytomegalic neurons in focal or hemispheric cortical dysplasia and to determine whether the activity of the mammalian target of rapamycin (mTOR) kinase is abnormally high in these cells.

METHODS

Microarray analysis of gene expression in large dysplastic cells microdissected from cortical dysplasia surgical specimens was used to identify markers of cytomegalic neurons. Immunohistochemistry and immunofluorescence analysis of cortical sections was used to validate the microarray results and to probe the activity of mTOR in cytomegalic neurons using phospho-specific antibodies directed against known mTOR targets.

RESULTS

We demonstrate that the neurofilament heavy chain is a reliable marker of cytomegalic neurons and that targets of the mTOR kinase, such as the ribosomal protein S6, eIF4G, and Akt, are hyperphosphorylated in these dysplastic neurons.

INTERPRETATION

We conclude that mTOR kinase hyperactivation is a molecular mechanism underlying the development of cytomegalic neurons. This finding may lead to the development of novel therapeutic approaches for childhood epilepsy associated with cortical dysplasia.

Seizure outcome after surgery for epilepsy due to focal cortical dysplastic lesions

Neocortical development is a highly complex process encompassing cellular proliferation, neuronal migration and cortical organization. At any time this process can be interrupted or modified by genetic or acquired factors causing malformations of cortical development (MCD). Epileptic seizures are the most common type of clinical manifestation, besides developmental delay and focal neurological deficits. Seizures due to MCD are frequently pharmacoresistant, especially those associated to focal cortical dysplasia (FCD). Surgical therapy results have been reported since 1971, however, currently available data from surgical series are still limited, mainly due to small number of patients, distinct selection of candidates and surgical strategies, variable pathological diagnosis and inadequate follow-up. This study addresses the possibilities of seizure relief following resection of focal cortical dysplasia, and the impact of presurgical evaluation, extent of resection and pathological findings on surgical outcome. We included 41 patients, 22 adults and 19 children and adolescents, with medically intractable seizures operated on from 1996 to 2002. All were submitted to standardized presurgical evaluation including high-resolution MRI, Video-EEG monitoring and ictal SPECT. Post-surgical seizure outcome was classified according to Engel's schema. Univariate and multivariate analysis were performed. Fifteen patients had temporal and 26 extratemporal epilepsies. Of the total 26 patients (63.4%) reached seizure-free status post-operatively. There was no correlation between outcome and age at surgery, duration of epilepsy, frequency of seizures, and pathological findings. There was, however, a clear correlation with topography of FCD (temporal versus extratemporal) and regional ictal EEG onset, on univariate as well as multivariate analysis.

Surgical outcome and predictive factors in adult patients with intractable epilepsy and focal cortical dysplasia

OBJECTIVES

To determine the surgical outcome and prognostic factors in adult patients with intractable epilepsy and focal cortical dysplasia (FCD).

MATERIALS AND METHODS

We retrospectively studied the operative outcome in 21 consecutive adult patients with FCD who underwent surgical treatment for intractable partial epilepsy.

RESULTS

The mean age at surgery was 32.7 years (range, 18-58 years). The median post-operative follow-up was 2.5 years. The FCD was extratemporal in 11 patients, involved the temporal lobe in 10 patients, and was multilobar in eight patients. Eleven patients (52%) were rendered seizure-free, four patients (19%) had >95% reduction in seizures, and two patients (10%) had an 80-94% reduction in seizures. A seizure-free outcome was associated with shorter duration of epilepsy (P = 0.02).

CONCLUSION

Adult patients with FCD may be candidates for surgical treatment of intractable partial epilepsy. Most individuals have neocortical, extrahippocampal seizures and approximately 50% of patients are rendered seizure-free.

Focal cortical dysplasia: a review of pathological features, genetics, and surgical outcome

Focal cortical dysplasia (FCD) is found in approximately one-half of patients with medically refractory epilepsy. These lesions may involve only mild disorganization of the cortex, but they may also contain abnormal neuronal elements such as balloon cells. Advances in neuroimaging have allowed better identification of these lesions, and thus more patients have become surgical candidates. Molecular biology techniques have been used to explore the genetics and pathophysiological characteristics of FCD. Data from surgical series have shown that surgery often results in significant reduction or cessation of seizures, especially if the entire lesion is resected.

Frequent association of cortical dysplasia in dysembryoplastic neuroepithelial tumor treated by epilepsy surgery

BACKGROUND

We report on our experience with epilepsy surgery in the treatment of localization-related epilepsy caused by dysembryoplastic neuroepithelial tumor (DNT) aimed at achieving the best seizure control.

METHODS

A retrospective analysis was performed on the pathological reports as well as on clinical data of 24 case patients with medically intractable epilepsy with DNT treated surgically between 1995 and 2000 at the Samsung Medical Center. Resective surgery was performed using subdural electrodes or intraoperative electrocorticography in all patients.

RESULTS

The mean follow-up period was 57.2 months. Two patients had rare seizures transiently after surgery but remained free from seizures after 6 months. Others remained completely free from seizures. There was a strong tendency of temporal lobe involvement (19 cases; 79.2%). Size of tumors located at medial temporal regions was significantly smaller than those at lateral temporal or frontal lobes (P < .05). A rather radical resection (tumor plus surrounding tissue showing active epileptogenicity) was performed in all but one case where only focal lesionectomy was done. In 20 of the 24 cases (83.3%), association of cortical dysplasia (CD) was found on pathological examination.

CONCLUSIONS

We conclude that DNT is frequently associated with CD, with a wide area of epileptogenic activity that might be related to the presence of CD around the DNT. Comprehensive preoperative investigations for accurate localization of epileptogenic activity, meticulous brain mapping, and a rather radical resection of pathological areas might be essential for the achievement of excellent seizure control in DNT-associated epilepsy.

Enhanced visualization of blurred gray-white matter junctions in focal cortical dysplasia by voxel-based 3D MRI analysis

PURPOSE

Focal cortical dysplasia (FCD), a frequent cause of partial epilepsy, is often associated with blurring of the gray-white matter junction in magnetic resonance images (MRI). To improve the recognition and delineation of FCD we developed a novel voxel-based image post-processing method for enhanced visualization of blurred gray-white matter junctions.

METHODS

Using standard algorithms of statistical parametric mapping software (SPM99) a T1-weighted MRI volume data set is normalized and segmented. The distribution of gray and white matter is analyzed on a voxelwise basis and compared with a normal database. Based on this analysis, a three-dimensional feature map is created which highlights brain areas with blurred gray-white matter transition. This method was applied to the MRI data of 25 epilepsy patients with histologically proven FCD.

RESULTS

In 18/25 patients the new feature maps clearly showed that the dysplastic lesions were accompanied by blurring of the gray-white matter junction. Combined with a formerly published method of voxel-based 3D MRI analysis, 21/25 FCD lesions were shown to be associated with either blurring or abnormal extension of gray matter beyond the normal cortical ribbon, including four cases with lesions not or incompletely recognized on conventional MRI.

CONCLUSIONS

The MRI post-processing presented here improves the visualization of FCD and may increase the diagnostic yield of MRI. Thereby, it provides a valuable additional diagnostic tool in the presurgical evaluation of epilepsy patients.

Surgical treatment of epilepsy in children caused by focal cortical dysplasia

Focal cortical dysplasia (FCD) is a congenital disorder of neuronal migration that is increasingly recognized as a common cause of seizures in children, occurring in 20-30% of all surgically treated cases of epilepsy in the pediatric population. Advances in neuroimaging have contributed to recognition of FCD. We report 15 children (9 female, 6 male) with FCD and surgically treated intractable epilepsy. In 9 cases, a surgical strategy of anatomic (frameless stereotactic) grid placement and physiologic (electrocorticography) resection was employed. Postoperative MRI scans were obtained, the pathologic specimen was graded according to the Brannstrom system, and seizure outcome was defined using the Engel classification. There were no deaths and no permanent morbidity. After, on average, 4 years since treatment, 10 children are seizure free, 2 are 2A, 2 are 2B and 1 is 3A. Predictors of good outcome are an MRI-defined lesion and increased cortical disorganization (higher Brannstrom grade). Subtotal resection did not preclude a seizure-free outcome.

Surgical Outcome of Epilepsy Caused by Cortical Dysplasia

PURPOSE

Cortical dysplasia (CD) is the second most common pathologic entity in surgically treated epilepsy. To delineate its surgical outcome and prognostic factors, we performed a retrospective analysis of patients operated on at a single institute.

METHODS

Between September 1994 and December 2000, 128 cases with CD were operated on at our institute. The male/female ratio was 85:43, and the mean age was 27 years (SD, 7.6 years). The mean postoperative follow-up period was 26.9 months (SD, 12.0 months). Seizure outcome and severity of CD were classified according to Engel's and Mischel's classifications, respectively. Severity of CD was mild in 69, moderate in 21, and severe in 38. Lobar distribution was temporal in 54, frontal in 48, and others in 26. Cortical resection, lobectomy, or hemispherectomy was done in all patients. Univariate analysis was done followed by multivariate analysis by using computerized statistical software.

RESULTS

Postoperative seizure outcome was Engel class I in 58 (45.3%), II in 17 (13.3%), III in 16 (12.5%), and IV in 37 (28.9%). Transient postoperative complications occurred in 14 (10.9%) patients without mortality or permanent neurologic impairment. Multivariate analysis revealed severity of CD and frontal lobe resection as independent prognostic factors for worse outcome (p = 0.001 and 0.003, respectively).

CONCLUSIONS

Epilepsy surgery for CD achieved 45.3% seizure-free rate with 10.9% transient postoperative complications in our institute. Worse postoperative seizure outcome was observed in cases with mild CD and frontal lobe resection.

Cortical laminar disorganization is correlated with severity of the cortical dysplasia and surgical outcome—experience with 150 cases

The aim of this study is to evaluate that the cortical laminar disorganization (CLD) and its correlation with the severity of the cortical dysplasia (CD) and surgical outcome. The cohort consists of 150 patients (101 males and 49 females) who underwent surgical resection of the epileptic area due to medically intractable epilepsy. Histologically, the CLD was divided into three grades according to the degree of disarrangement of the clear-cut six-layered cortex and the pathological features on MAP2 and NeuN immunostaining; normal to mild, moderate and severe CLD in 58 (38.7%), 47 (31.3%) and 45 (30.0%) cases, respectively. The histopathological grading of CLD had significant correlation with severity of CD (p<0.001), number of single heterotopic neurons in white matter (p=0.009), presence of neurons in molecular layer (p<0.001), persistent subpial granular cells (p=0.017), cytomegalic neurons (p<0.001) and balloon cells (p<0.001), and gray-white matter blurring (p<0.001), and had inverse correlation with surgical outcome (<0.001). Since statistically correlated with the known parameters of CD and surgical outcome, the grading of CLD could be used as another histological parameter for CD.

Long-term outcome after epilepsy surgery for focal cortical dysplasia

OBJECT

Reports of outcomes for surgical treatment of cortical dysplasia associated with epilepsy are conflicting due to the inclusion of patients with a wide range of malformations of cortical development. The authors report their experience and the long-term outcome for a subgroup of patients with the histopathological diagnosis of focal cortical dysplasia of Taylor.

METHODS

The records of 22 patients with focal cortical dysplasia of Taylor (15 with the balloon-cell type and seven with the nonballoon-cell type) were reviewed. There were 11 female and 11 male patients whose mean age was 26 +/- 17.6 years (mean +/- standard deviation [SD]) at surgery. The details of their epilepsy evaluation and resection were analyzed. Extent of resection was preoperatively planned using information obtained from long-term intracranial monitoring (15 patients) and/or more definitively determined by histopathologically proven clear margins during resection when feasible (12 patients). The mean duration of follow up was 6.3 +/- 5.1 years (mean +/- SD, range 0.5-15.6 years). Risk factors for epilepsy were trauma (seven patients) or meningoencephalitis (one patient); 14 patients (64%) had no obvious risk factors. The mean age at seizure onset was 9.2 years and the mean duration of their epilepsy was 16.1 +/- 9 years. In two patients there were no adverse findings on magnetic resonance (MR) imaging. In 15 patients (68%), the epileptogenic zone identified on long-term intracranial monitoring extended beyond the abnormality observed on MR images. Focal resection (lesion plus margins) was performed in 14 patients (64%), whereas eight (36%) underwent partial/tailored lobectomy. Two patients underwent multiple subpial transections in addition to partial lesionectomy because their lesions involved the sensorimotor cortex. In these two, functional MR imaging confirmed a normal functional anatomy despite the presence of the cortical dysplasia. Eleven (92%) of 12 patients who underwent resection guided by histopathologically proven clear margins and three (43%) of seven patients who underwent histopathologically proven subtotal resection have remained seizure free. Evidence of clear margins was significantly associated with an improved seizure outcome (p = 0.003). Postoperatively, expected deficits included nondisabling visual field defects, which occurred in three patients (14%), and transient sensorimotor deficits, which appeared in five (23%). Two patients had meningitis, which was successfully treated with antibiotics. Overall, 16 patients (73%) are either seizure free (13 patients), have rare nondisabling partial seizures (one patient), or had one seizure after their medication was changed (two patients). Thirteen patients (59%) have discontinued anticonvulsant medications or are being maintained on monotherapy. Of five patients (23%), two have had rare disabling seizures or significant reduction in their seizure frequency (three patients). One patient's seizures have remained the same.

CONCLUSIONS

Focal cortical dysplasias are a distinct subgroup of malformations of cortical development and have a favorable outcome after resection. The epileptogenic zone often extends beyond the abnormality found on neuroimaging. Resection of the epileptogenic zone guided by histopathologically proven clear margins is associated with an improved seizure outcome.

Surgery for drug resistant partial epilepsy in children with focal cortical dysplasia: anatomical-clinical correlations and neurophysiological data in 10 patients

OBJECTIVE

To analyse a population of children with focal cortical dysplasia operated on for drug resistant partial epilepsy, with emphasis on clinical features, seizure semiology, interictal and ictal EEG and stereo EEG findings, histological and topographical characteristics of the lesions, extension and localisation of cerebral excision, and its postoperative effect on seizure frequency.

METHODS

10 patients were studied, aged between 26 months and 11 years (median 6 years). Magnetic resonance imaging (MRI) abnormalities were unilobar (temporal 3, frontal 2), bilobar (2), or multilobar (1); the two patients with negative MRI suffered from frontal seizures. Presurgical diagnostic steps varied in complexity and invasiveness depending on the anatomical/electrical/clinical features of each patient. In four patients they included only scalp video EEG monitoring, and in six, also invasive recordings using stereotactically implanted intracerebral electrodes. Surgery consisted of corticectomy plus lesionectomy in all cases.

RESULTS

70% of the patients were seizure-free after a minimum postoperative follow up of 25 months. These included three patients with temporal lesions and four of seven patients with other lobar or multilobar extratemporal localisation. One patient had improvement in seizure control. Outcome was poor in multilobar patients, but a class Ia outcome was obtained in one case after partial lesionectomy associated with bilobar corticectomy. All patients showed developmental improvement.

CONCLUSIONS

Analysis of the data in these patients allowed the production of an "anatomical-clinical concordance" list, which appeared to be correlated with the diagnostic steps performed. Carrying out a stereo EEG exploration in the most complex cases proved useful in defining the epileptogenic zone in extratemporal and multilobar epilepsies. Stereo EEG recordings facilitated a tailored resection of extralesional cortex.

Automated detection of gray matter malformations using optimized voxel-based morphometry: a systematic approach

Malformations of cortical development (MCD) are a recognized cause of epilepsy. Their special significance lies in the fact that, once detected and delineated, they are amenable to surgical removal. However, diagnosis from high-resolution MRI is still difficult, time-consuming, and highly dependent on individual expertise. We have recently proposed a simple procedure to detect cortical dysplasias, using automated procedures available within SPM99 (Wellcome Department, University College London, UK). Here, we aimed to systematically determine the best combination of processing parameters, using an optimized voxel-based morphometry approach. We included 20 patients with a known MCD and compared them to a normal database of 53 healthy, age- and gender-matched controls. The approaches taken during spatial normalization and a number of other parameters were systematically altered in order to find the best combination of parameters. Overall, 99 different approaches were evaluated in different ways. As far as possible, automatic processing and evaluation steps were used. With the number of candidate regions for MCD limited to five per patient, the best approaches resulted in the correct identification of up to 16 of 20 malformations. However, a number of approaches failed to perform well. The reasons for these failures and the implications this has for other studies are discussed. We conclude that voxel-based morphometry is able to detect cortical malformations with a high degree of accuracy. However, specific problems seem to arise when using an optimized protocol for voxel-based morphometry, indicating that this protocol may not be optimal for all voxel-based studies on brain morphology. Our approach, involving systematic alterations of parameters and evaluation, may be useful for other studies.

Focal cortical dysplasia and intractable epilepsy in adults: clinical, EEG, imaging, and surgical features

PURPOSE

The clinical features of focal cortical dysplasia (FCD) in adults are poorly understood. The purpose of this report is to describe the clinical, electrographic, and neuroimaging characteristics of adults with FCD undergoing surgical resection for intractable epilepsy.

METHODS

Case series of 55 patients, aged 17-57 years, with a histopathological diagnosis of FCD. Medical history, neurological examination, non-invasive video-EEG, neuroimaging, and surgical outcome data were analyzed retrospectively.

RESULTS

There were 36 patients with temporal, 19 with extra-temporal lobe resections. Mean age at surgery was 29 years. Mean age at epilepsy onset was 10 years. Dual pathology was seen in 56% of patients, with 68% of these having hippocampal sclerosis (HS). Epilepsy risk factors included febrile seizures (16%), head trauma (16%), CNS infections (11%), and perinatal stroke (4%). Interictal EEG showed regional epileptiform activity in 89% of patients. Only 24% were diagnosed with FCD pre-operatively. Of those with dual pathology, only 6% were suspected of having FCD pre-operatively. Of those patients with >12 months follow-up, surgical outcomes were as follows: 65% seizure-free, 19% significant improvement, 16% without significant improvement.

CONCLUSIONS

In this series of adult patients with intractable epilepsy and FCD, a significant number have other seizure risk factors, normal neurological examinations and neuroimaging, and regional EEG findings. Dual pathology was common in patients with FCD. FCD should be considered as an etiology of epilepsy even in patients whose evaluation suggests other mechanisms.

Cortical dysplasia and epilepsy: functional imaging using single photon emission computed tomography and positron emission tomography

Functional imaging using single photon emission CT and positron emission tomography have made important contributions to the evaluation of patients with medically intractable epilepsy and cortical dysplasia by identifying patients who previously were not considered surgical candidates. This article reviews the role of functional imaging in the presurgical evaluation of this patient population.

Surgery for focal cortical dysplasia

Interest in surgery for focal cortical dysplasia has grown with the enhanced ability to detect these lesions preoperatively with modern imaging techniques. This article focuses on the surgical management of epilepsy associated with focal cortical dysplasia. The authors highlight the approaches practiced at Yale University, review their recent series of operative cases, and discuss a representative case example to illustrate important aspects of surgical strategy.

Epileptogenesis in the Dysplastic Brain: A Revival of Familiar Themes

Brain malformations are now widely recognized in many forms of epilepsy. To investigate how malformed brain regions participate in the generation of seizure activity researchers have focused on animal models. Here we describe recent advances in this field.