Uncovered primary seizure foci in Lennox-Gastaut syndrome after corpus callosotomy

Epilepsy surgery in developmental and epileptic encephalopathies

Developmental and epileptic encephalopathies (DEEs) present significant treatment challenges due to frequent, drug-resistant seizures and comorbidities that impact quality of life. DEEs include both developmental encephalopathy from underlying pathology and epileptic encephalopathy where seizures exacerbate cognitive and behavioral impairments. Classification by syndrome and etiology is essential for therapy and prognosis, with common syndromes like infantile epileptic spasms syndrome and Dravet syndrome having specific first-line treatments. Etiologies are predominantly genetic, structural, or combined, with targeted therapies increasingly available. Surgery aims to improve seizure control but also may improve development, if the epileptic encephalopathy can be ameliorated. Timely intervention can reduce seizures and epileptiform discharges, maximizing developmental potential and allowing reduction in antiseizure medication. In cases requiring extensive resections, new deficits may be offset by developmental gains. Studies indicate that parents are generally willing to accept some deficits for significant seizure reduction.

Development of localized interictal epileptiform discharges following vagus nerve stimulation for lennox-gastaut syndrome: a case report

Background

Lennox-gastaut syndrome (LGS) is an epileptic encephalopathy often associated with behavioral and psychiatric disorders. Vagus nerve stimulation (VNS) has been approved effective for LGS treatment. Surgical resection is also an option for LGS patients with focal pathology, offering a high probability of seizure control. However, it is challenging to accurately localize the seizure focus.

Case presentation

The case presented here is a 19-year-old male with a 16-year history of epilepsy with comorbid severe cognitive and psychiatric disorders. He was diagnosed with LGS due to generalized slow spike-wave discharges and multiple seizure types. He was treated with VNS in 2017 at the age of 15. After that, the frequency of the short tonic seizures decreased from 4–5 times per day to 2–5 times per year, and the generalized tonic–clonic seizure pattern did not recur, which had a frequency of 2–4 times per month before the surgery. In 2019, the generalized abnormal interictal epileptiform discharges changed to be localized in the right frontal–temporal lobe at the age of 17 years (2019).

Conclusions

This case report suggested that the generalized epileptiform discharges evolve into localized discharges after VNS treatment, which may help reveal the primary seizure focus for resection surgery in patients with LGS.

Corpus Callosotomy in the Modern Era: Origins, Efficacy, Technical Variations, Complications, and Indications

Corpus callosotomy is among the oldest surgeries performed for drug-resistant epilepsy (DRE). First performed in 1940, various studies have since assessed its outcomes in various patient populations in addition to describing different extents of sectioning and emerging technologies (i.e. endoscopic, laser interstitial thermal therapy, and radiosurgery). In order to capture the current state and offer a reappraisal, we comprehensively review corpus callosotomy's origins, efficacy for various seizure types, technical variations, complications, and indications and compare the procedure to vagus nerve stimulation therapy which has similar indications. We consider corpus callosotomy to be a safe and efficacious procedure that should be considered by clinicians when appropriate. Furthermore, it can also play an important role in treating patients with DRE in low-to-middle-income countries where resources are limited.

Corpus Callosotomy for Controlling Epileptic Spasms: A Proposal for Surgical Selection

In 1940, van Wagenen and Herren first proposed the corpus callosotomy (CC) as a surgical procedure for epilepsy. CC has been mainly used to treat drop attacks, which are classified as generalized tonic or atonic seizures. Epileptic spasms (ESs) are a type of epileptic seizure characterized as brief muscle contractions with ictal polyphasic slow waves on an electroencephalogram and a main feature of West syndrome. Resection surgeries, including frontal/posterior disconnections and hemispherotomy, have been established for the treatment of medically intractable ES in patients with unilaterally localized epileptogenic regions. However, CC has also been adopted for ES treatment, with studies involving CC to treat ES having increased since 2010. In those studies, patients without lesions observed on magnetic resonance imaging or equally bilateral lesions predominated, in contrast to studies on resection surgeries. Here, we present a review of relevant literature concerning CC and relevant adaptations. We discuss history and adaptations of CC, and patient selection for epilepsy surgeries due to medically intractable ES, and compared resection surgeries with CC. We propose a surgical selection flow involving resection surgery or CC as first-line treatment for patients with ES who have been assessed as suitable candidates for surgery.

Intracranial EEG Biomarkers for Seizure Lateralization in Rapidly-Bisynchronous Epilepsy After Laser Corpus Callosotomy

Objective: It has been asserted that high-frequency analysis of intracranial EEG (iEEG) data may yield information useful in localizing epileptogenic foci. Methods: We tested whether proposed biomarkers could predict lateralization based on iEEG data collected prior to corpus callosotomy (CC) in three patients with bisynchronous epilepsy, whose seizures lateralized definitively post-CC. Lateralization data derived from algorithmically-computed ictal phase-locked high gamma (PLHG), high gamma amplitude (HGA), and low-frequency (filtered) line length (LFLL), as well as interictal high-frequency oscillation (HFO) and interictal epileptiform discharge (IED) rate metrics were compared against ground-truth lateralization from post-CC ictal iEEG. Results: Pre-CC unilateral IEDs were more frequent on the more-pathologic side in all subjects. HFO rate predicted lateralization in one subject, but was sensitive to detection threshold. On pre-CC data, no ictal metric showed better predictive power than any other. All post-corpus callosotomy seizures lateralized to the pathological hemisphere using PLHG, HGA, and LFLL metrics. Conclusions: While quantitative metrics of IED rate and ictal HGA, PHLG, and LFLL all accurately lateralize based on post-CC iEEG, only IED rate consistently did so based on pre-CC data. Significance: Quantitative analysis of IEDs may be useful in lateralizing seizure pathology. More work is needed to develop reliable techniques for high-frequency iEEG analysis.

Epilepsy Surgery is a Viable Treatment for Lennox Gastaut Syndrome

Lennox Gastaut Syndrome (LGS) is a severe developmental epileptic encephalopathy with onset in childhood characterized by multiple seizure types and characteristic electroencephalogram findings. The majority of patients develop drug resistant epilepsy, defined as failure of 2 appropriate anti-seizure medications used at adequate doses. Epilepsy surgery can reduce seizure burden, in some cases leading to seizure freedom, and improve neuro-developmental outcomes and quality of life. Epilepsy surgery should be considered for all patients with drug resistant LGS. Herein, we review current surgical treatment options for patients with LGS, both definitive and palliative, including: focal cortical resection, vagus nerve stimulation and corpus callosotomy. Newer neuromodulation techniques will be explored, as well as the concept of LGS as a secondary network disorder.

Recent Aspects of Pediatric Epilepsy Surgery

Surgery has been and is now a well-established treatment indicated for adults and children with drug-resistant epilepsy (DRE). The surgical landscape for children with DRE appears to be expanding, and surgical cases of pediatric epilepsy have increased significantly in the past decade, contrary to adult epilepsy. Several fundamental changes have led to the widespread surgical treatment for DRE in children, based on a risk-benefit analysis of pediatric epilepsy surgery, and a change in our overall approach to evaluation. There are unique and age-related differences associated with pediatric epilepsy surgery, characterized by different types of etiologies, concerns for developmental progress, and safety issues. Indications for “pediatric epilepsy surgery” have been broadened to include a wide spectrum of etiologies without excluding children with “generalized” seizures, “generalized or multifocal eletroencephlography”, or patients with contra-lateral epileptiform activity or magnetic resonance imaging abnormalities. Furthermore, epilepsy surgery is increasingly considered in infancy and early childhood, which has similar surgical outcomes as the case of late childhood, in an effort to improve the eventual development outcome. Seizure freedom, or at least seizure reduction, is an excellent result with resolution of the associated epileptic encephalopathy, normalization of the EEG, and decrease in the total epileptic burden in the pediatric field.

Epilepsy Surgery in Children versus Adults

Epilepsy is one of the most common chronic neurological disorder affecting 6–7 per 1000 worldwide. Nearly one-third of patients with newly diagnosed epilepsy continue to have recurrent seizures despite adequate trial of more than two anti-seizure drugs : drug-resistant epilepsy (DRE). Children with DRE often experience cognitive and psychosocial co-morbidities requiring more urgent and aggressive treatment than adults. Epilepsy surgery can result in seizure-freedom in approximately two-third of children with improvement in cognitive development and quality of life. Understanding fundamental differences in etiology, co-morbidity, and neural plasticity between children and adults is critical for appropriate selection of surgical candidates, appropriate presurgical evaluation and surgical approach, and improved overall outcome.

Treatment-resistant Lennox-Gastaut syndrome: therapeutic trends, challenges and future directions

Lennox-Gastaut syndrome is a severe, childhood-onset electroclinical syndrome comprised of multiple seizure types, intellectual and behavioral disturbances and characteristic findings on electroencephalogram of slow spike and wave complexes and paroxysmal fast frequency activity. Profound morbidity often accompanies a common and severe seizure type, the drop attack. Seizures often remain refractory, or initial treatment efficacy fades. Few individuals are seizure free despite the development of multiple generations of antiseizure medications over decades and high-level evidence on several choices. Approved medications such as lamotrigine, topiramate, rufinamide, felbamate and clobazam have demonstrated efficacy in reducing seizure burden. Cannabidiol has emerged as a promising investigational therapy with vast social interest yet lacks a standard, approved formulation. Palliative surgical procedures, such as vagal nerve stimulation and corpus callosotomy may provide reduction in total seizures and drop attacks. Emerging evidence suggests that complete callosotomy provides greater improvement in seizures without additional side effects. Etiologies such as dysplasia or hypothalamic hamartoma may be amenable for focal resection and thus offer potential to reverse this devastating epileptic encephalopathy.

Resective surgery combined with corpus callosotomy for children with non-focal lesional Lennox-Gastaut syndrome

BACKGROUND

The first prospective trial for resective surgery combined with corpus callosotomy (CCT) was performed to investigate the outcomes of the combined surgery in children with Lennox-Gastaut syndrome (LGS) without focal lesion on brain MRI.

METHODS

This study enrolled 68 children with LGS and without focal lesion on brain MRI, of which 25 received medicine (medicine group) and 43 underwent surgery (surgery group), including 20 with exclusively resective surgery (exclusively resection subgroup) and 23 with resective surgery combined with CCT (combined CCT subgroup). All patients were followed for 3-5 years.

RESULTS

Significant differences in seizure control were observed between the medicine group and the exclusively resection subgroup and combined CCT subgroup at the 1-year, 3-year, and 5-year follow-ups. There was a trend that the children with resection combined with CCT had better seizure control than those with exclusively resection at the three follow-ups, but this could not be verified by the statistical method used. Furthermore, significant differences were not observed in seizure control between children with different MRI findings, age at surgery, or pathology in the surgery group. The percentage of long-term seizure-free did not remain as high as the percentage of early stage seizure-free at 1-year follow-up. However, the children with combined CCT surgery demonstrated more postoperative improvement than the children with resective surgery alone based on the mean QOL score (10.78 vs. 5.75, p = 0.0152) and full-scale IQ (7.91 vs. 4.55, p = 0.0446).

CONCLUSIONS

Resective surgery combined with CCT can provide favorable seizure control and obvious improvements in QOL and IQ in children with LGS. This combined approach can be performed in carefully selected LGS children without focal lesions and can localize the epileptogenic zone following a comprehensive preoperative evaluation.

Combined surgical intervention with vagus nerve stimulation following corpus callosotomy in patients with Lennox-Gastaut syndrome

BACKGROUND

Lennox-Gastaut syndrome (LGS) is a drug-resistant pediatric epilepsy characterized by multiple seizure types, including drop attacks (DAs). Palliative procedures such as corpus callosotomy (CC) and vagus nerve stimulation (VNS) may be effective for adequate seizure control in LGS patients who are not candidates for resective surgery. We evaluated the efficacy of the combination of these two procedures for LGS-related seizures.

METHOD

Ten patients with LGS (age 3-30 years at VNS implantation) underwent CC and subsequent VNS. We evaluated surgical outcomes, particularly with respect to the efficacy of VNS on seizure reduction rates for different residual seizure types after CC. We compared clinical parameters, including sex, age, seizure duration, history, MRI findings, extent of CC, number of antiepileptic drugs, and neuropsychological states, between VNS responders and non-responders to predict satisfactory seizure outcomes with respect to residual seizures after CC.

FINDINGS

VNS was effective for residual seizures regardless of seizure type (except for DAs) after CC in patients with LGS. Six of ten (60%) patients had a satisfactory seizure outcome (≥50% seizure reduction) for all residual seizure types after VNS. Two of ten (20%) patients were seizure-free at 12 months post-VNS. Even those patients that were non-responders, with respect to all seizures including DAs, after prior CC showed favorable responses to subsequent VNS. Compared to VNS, excellent seizure outcomes for DAs were achieved after CC in seven of nine (77.8%) patients with DAs. Among the clinical parameters, only conversation ability before VNS was significantly different between responders and non-responders (p = 0.033).

CONCLUSION

Combined VNS and prior CC produced satisfactory seizure outcomes in LGS patients with different seizure types, including DAs. Even non-responders to prior CC responded to subsequent VNS for residual seizures, except for DAs. There is a greater likelihood that these procedures may be more feasible in patients who possess conversation ability prior to VNS.

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.

Conceptualizing lennox-gastaut syndrome as a secondary network epilepsy

Lennox–Gastaut Syndrome (LGS) is a category of severe, disabling epilepsy, characterized by frequent, treatment-resistant seizures, and cognitive impairment. Electroencephalography (EEG) shows characteristic generalized epileptic activity that is similar in those with lesional, genetic, or unknown causes, suggesting a common underlying mechanism. The condition typically begins in young children, leaving many severely disabled with recurring seizures throughout their adult life. Scalp EEG of the tonic seizures of LGS is characterized by a diffuse high-voltage slow transient evolving into generalized low-voltage fast activity, likely reflecting sustained fast neuronal firing over a wide cortical area. The typical interictal discharges (runs of slow spike-and-wave and bursts of generalized paroxysmal fast activity) also have a “generalized” electrical field, suggesting widespread cortical involvement. Recent brain mapping studies have begun to reveal which cortical and subcortical regions are active during these “generalized” discharges. In this critical review, we examine findings from neuroimaging studies of LGS and place these in the context of the electrical and clinical features of the syndrome. We suggest that LGS can be conceptualized as “secondary network epilepsy,” where the epileptic activity is expressed through large-scale brain networks, particularly the attention and default-mode networks. Cortical lesions, when present, appear to chronically interact with these networks to produce network instability rather than triggering each individual epileptic discharge. LGS can be considered as “secondary” network epilepsy because the epileptic manifestations of the disorder reflect the networks being driven, rather than the specific initiating process. In this review, we begin with a summation of the clinical manifestations of LGS and what this has revealed about the underlying etiology of the condition. We then undertake a systematic review of the functional neuroimaging literature in LGS, which leads us to conclude that LGS can best be conceptualized as “secondary network epilepsy.”

[Resection of frontal lobe epileptogenic foci identified after corpus callosotomy: long term results]

OBJECTIVES

To analyse the results of resective surgery in patients in whom it was possible to identify a frontal epileptogenic focus through corpus callosotomy.

MATERIAL AND METHODS

Data from patients suffering drug-resistant epilepsy showing persistence of disabling seizures after undergoing corpus callosotomy and subsequent treatment with frontal lobe resective surgery were prospectively reviewed. Classifications according to Engel's scale before and after each intervention were evaluated, as were the percentages of seizure reduction. Additionally, the satisfaction of family members with surgical outcomes was also assessed.

RESULTS

Eleven patients were identified. After a median follow-up period of 7 years (IQR: 3-8 years), 63.6% of patients showed improvement of seizures according to Engel's scale, 27.2% remained unchanged and one worsened. One patient was categorised as class i, 8 as class ii, one as class iii and one as class iv. The percentage reduction in the number of seizures was over 90% in 54.5% of patients, between 50% and 90% in 36.4% and less than 50% in 9.1%. Family satisfaction was reported as good or excellent in 90.9% of cases.

CONCLUSIONS

In addition to providing better seizure control, corpus callosotomy also appears to be a diagnostic tool allowing the identification of potential targets for resective surgery. Therefore, it should be considered upon suspicion of a frontal epileptogenic focus which could be surgically treated.

Update on the management of Lennox-Gastaut syndrome

Lennox-Gastaut syndrome is a severe childhood epilepsy disorder characterized by encephalopathy and multiple, often intractable, seizure types. The drop attack is the most frequently recognizable seizure type in this patient population, and is also the most dangerous physically, thus severely limiting quality of life. The diagnosis is confirmed by electroencephalography, for which the classic pattern is a slow 2.5 Hz generalized spike-and-wave. Newer pharmacologic treatments include rufinimide and clobazam. However, antiepileptic drugs are often exhausted in pursuit of seizure control requiring nonpharmacologic interventions. These include dietary therapies, vagus nerve stimulation, and epilepsy surgery, including corpus callosotomy and focal curative resection. Although large lobar resections are often required, very localized, discrete resections may be possible, as in symptomatic Lennox-Gastaut syndrome (specifically, hypothalamic hamartoma). We review the history of the disease and current management options.