Critical review of palliative surgical techniques for intractable epilepsy

Delving into the significance of the His289Tyr single-nucleotide polymorphism in the glutamate ionotropic receptor kainate-1 (Grik1) gene of a genetically audiogenic seizure model

Genetic abnormalities affecting glutamate receptors are central to excitatory overload-driven neuronal mechanisms that culminate in seizures, making them pivotal targets in epilepsy research. Increasingly used to advance this field, the genetically audiogenic seizure hamster from Salamanca (GASH/Sal) exhibits generalized seizures triggered by high-intensity acoustic stimulation and harbors significant genetic variants recently identified through whole-exome sequencing. Here, we addressed the influence of the missense single-nucleotide polymorphism (C9586732T, p.His289Tyr) in the glutamate receptor ionotropic kainate-1 (Grik1) gene and its implications for the GASH/Sal seizure susceptibility. Using a protein 3D structure prediction, we showed a potential effect of this sequence variation, located in the amino-terminal domain, on the stability and/or conformation of the kainate receptor subunit-1 protein (GluK1). We further employed a multi-technique approach, encompassing gene expression analysis (RT-qPCR), Western blotting, and immunohistochemistry in bright-field and confocal fluorescence microscopy, to investigate critical seizure-associated brain regions in GASH/Sal animals under seizure-free conditions compared to matched wild-type controls. We detected disruptions in the transcriptional profile of the Grik1 gene within the audiogenic seizure-associated neuronal network. Alterations in GluK1 protein levels were also observed in various brain structures, accompanied by an unexpected lower molecular weight band in the inferior and superior colliculi. This correlated with substantial disparities in GluK1-immunolabeling distribution across multiple brain regions, including the cerebellum, hippocampus, subdivisions of the inferior and superior colliculi, and the prefrontal cortex. Notably, the diffuse immunolabeling accumulated within perikarya, axonal fibers and terminals, exhibiting a prominent concentration in proximity to the cell nucleus. This suggests potential disturbances in the GluK1-trafficking mechanism, which could subsequently affect glutamate synaptic transmission. Overall, our study sheds light on the genetic underpinnings of seizures and underscores the importance of investigating the molecular mechanisms behind synaptic dysfunction in epileptic neural networks, laying a crucial foundation for future research and therapeutic strategies targeting GluK1-containing kainate receptors.

Palliative Surgery for Drug-Resistant Epilepsy in Adult Patients. A Systematic Review of the Literature and a Pooled Analysis of Outcomes

BACKGROUND

Several types of palliative surgery to treat drug-resistant epilepsy (DRE) have been reported, but the evidence that is available is insufficient to help physicians redirect patients with DRE to the most appropriate kind of surgery.

METHODS

A systematic search in the PubMed and Scopus databases was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines to compare different clinical features, outcomes, and complications of adult patients submitted to callosotomy, vagal nerve stimulation, multiple subpial transections, deep brain stimulation, or responsive neurostimulation.

RESULTS

After 3447 articles were screened, 36 studies were selected, including the data of 1628 patients: 76 were treated with callosotomy, 659 were treated with vagal nerve stimulation, 416 were treated with deep brain stimulation, and 477 were treated with responsive neurostimulation. No studies including patients treated with multiple subpial transections met the inclusion criteria. The global weighted average seizure frequency reduction was 50.23%, and the global responder rate was 52.12%. There were significant differences among the palliative surgical procedures in term of clinical features of patients and epilepsy, seizure frequency reduction, and percentage of responders. Complications were differently distributed as well.

CONCLUSIONS

Our analysis highlights the necessity of prospective studies, possibly randomized controlled trials, to compare different forms of palliative epilepsy surgery. Moreover, by identifying the outcome predictors associated with each technique, the best responder may be profiled for each procedure.

Neurological results of the modified treatment of epilepsy by stimulation of the vagus nerve

INTRODUCTION

The vagus nerve stimulation (VNS) is used for treatment of drug-resistant epilepsy but laryngeal side effects are common. We tried to improve VNS by modifying the implantation procedure. The aim was to reduce the rate of side effects that have prevented using VNS to its full capacity.

METHODS

We operated on 74 pediatric patients for VNS device implantation using a modified surgical protocol incorporating lower neck incision for electrode placement and 36 patients who were operated by standard technique were used for control group. We retrospectively analyzed reduction in frequency of seizures, reduction in severity of seizures (assessed by the shortened Ictal/post-ictal subscale of the Liverpool Seizure Severity Scale that included falling to the ground, postictal headache and sleepiness, incontinence, tongue biting, and injury during attack).

RESULTS

Using the new implantation technique, side effects related directly to VNS therapy occurred in six cases (8.1%) showing statistically sound improvement over the standard implantation technique (p ˂ 0.05). To achieve good results, the maximum stimulation (3.5 mA) was used in 24 patients (32.4%), with no laryngeal side effects detected. Twelve patients (16.2%) were seizure-free after the first year of VNS treatment. 74.3% of patients experienced a 50% reduction in seizure frequency and improved ictal or postictal activity.

CONCLUSION

To minimize laryngeal complications in implantation surgery for VNS devices, the surgical technique may be modified, and lower neck incision could be used. A low rate of laryngeal side effects allows using the VNS device to its full electrical capacity.

Failed epilepsy surgery: is this the end?

Resective epilepsy surgery can lead to sustained seizure control in 70-80% of patients evaluated for epilepsy surgery, indicating that up to 30% of patients still have recurrent seizures after surgery. Definitions of failed epilepsy surgery vary amongst studies. This review focuses on seizure outcome predictors after reoperation, possible mechanisms of failure and best management for this difficult patient population.

Knowledge and Attitudes About Epilepsy Surgery Among Family Doctors in Ontario

BACKGROUND

Approximately 30% of patients with epilepsy have medically intractable seizures, and a proportion of them are candidates for surgical treatment. The efficacy and safety of epilepsy surgery have been supported by a large number of studies, yet only a small minority of such patients in Ontario receive surgery.

METHODS

Family physicians in Ontario were surveyed regarding demographics, referral practices and general knowledge about epilepsy surgery. Four hundred surveys were mailed to randomly selected family physicians using contact information from the College of Physicians and Surgeons of Ontario website.

RESULTS

The response rate was 50%. The majority of family physicians (81%) always refer patients with epilepsy, most often to neurologists. General knowledge of epilepsy was mixed, with 53.7% feeling that surgery should be considered in selected cases for the treatment of epilepsy, though 53.2% did not know what type of epilepsy could be surgically treated.

CONCLUSIONS

The results suggest a relatively low level of knowledge among family physicians in terms of when surgery ought to be considered, the types of epilepsy that are amenable to surgical treatment and the risks and benefits of epilepsy surgery. A lack of knowledge in these areas may partly underlie the low referral rates of epilepsy patients, though the results show that the majority of family physicians refer their patients with epilepsy to neurologists. Other factors must be considered, such as access to neurologists, epileptologists and surgical resources. Education campaigns directed at family physicians may improve knowledge and change referral practices. Future studies need to examine these possibilities.

Reappraisal of corpus callosotomy

PURPOSE OF REVIEW

Corpus callosotomy is a palliative surgical treatment modality that has gone in and out of favor. The purpose of this review is to summarize the studies of callosotomy in the past years as a treatment for severe drug-resistant epilepsy with traumatizing drop attacks, mostly in children and also in some adults. The aim is also to discuss knowledge gaps and suggest how these could be addressed.

RECENT FINDINGS

Lately, a number of callosotomy series, mostly retrospective and single center, have included 289 operated patients. A few series have included nonoperated controls; one prospective long-term series is national and population based. Seizure outcome is shown to be comparable to that earlier reported, with best effect against drop attacks. There is no consensus on whether anterior or complete callosotomy is to be preferred. In a meta-analysis of callosotomy versus vagal nerve stimulation, callosotomy led to better seizure outcome. Diffusion tensor imaging may be a promising tool to analyze the completeness of the procedure.

SUMMARY

Callosotomy remains an effective palliative procedure. Many unresolved issues, such as prognostic indicators, nonseizure-related outcomes, whether to choose anterior or complete callosotomy, and outcomes and adverse effects in adults, need to be studied in prospective, preferably multicenter studies.

Treatment of epilepsy by stimulation of the vagus nerve from Head-and-Neck surgical point of view

OBJECTIVES/HYPOTHESIS

The current article is dedicated to the surgical aspect of the vagus nerve stimulation (VNS) and our efforts to improve the surgical technique. The aim was to reduce the side effect/surgical complication rate as well as the time needed for this surgery.

STUDY DESIGN

A case series.

METHODS

The surgical data of 72 consecutive patients (age 4-14) who were operated for VNS device implantation from 2007 to 2014 were collected and analyzed. We designed the new surgical protocol that was implemented in all 72 cases and analyzed postsurgical side effects/complication rates. This protocol suggests low neck incision, detecting the vagus between the heads of the sternocleidomastoid muscle, a submuscular pocket for the device, and a short tunnel between it and the vagus electrodes.

RESULTS

The implantation took about 40 minutes; 4.2% of the patients (n = 3) were afflicted by complications related to surgery; and one patient (1.4%) suffered from hardware malfunctions. Side effects related to VNS therapy itself occurred in seven cases (6.9%).

CONCLUSION

To minimize laryngeal complications in implantation surgery for VNS devices, the surgical technique should be significantly modified, and lower neck incision could be implemented together with a submuscular pocket for the battery.

LEVEL OF EVIDENCE

4.

Vagus nerve stimulator in patients with epilepsy: indications and recommendations for use

Epilepsy comprises a set of neurologic and systemic disorders characterized by recurrent spontaneous seizures, and is the most frequent chronic neurologic disorder. In patients with medically refractory epilepsy, therapeutic options are limited to ablative brain surgery, trials of experimental antiepileptic drugs, or palliative surgery. Vagal nerve stimulation is an available palliative procedure of which the mechanism of action is not understood, but with established efficacy for medically refractory epilepsy and low incidence of side-effects. In this paper we discuss the recommendations for VNS use as suggested by the Brazilian League of Epilepsy and the Scientific Department of Epilepsy of the Brazilian Academy of Neurology Committee of Neuromodulation.