Vagus nerve stimulation in drug-resistant epilepsy: the efficacy and adverse effects in a 5-year follow-up study in Iran

Applications of magnetic resonance-guided laser interstitial thermal therapy in disconnective epilepsy surgery

Minimally invasive surgical techniques, such as MR-guided laser interstitial thermal therapy (LITT), have emerged as promising alternatives to open disconnective surgeries in drug-resistant epilepsy (DRE). This review synthesizes current literature on the application of LITT for corpus callosal disconnection and functional hemispheric disconnection. Studies highlight LITT's effectiveness for achieving seizure control and functional outcomes, often with reduced complications compared to traditional open procedures. Challenges include technical limitations to achieving total disconnection and adequate assessment of disconnection postoperatively. The literature is largely composed of observational studies and there is a need for rigorous, multi-center trials to establish robust guidelines and improve generalizability in clinical practice. There is also a need for a more robust exploration of how patient-specific factors contribute to response or nonresponse to intervention.

Evaluating the Efficacy of Vagus Nerve Stimulation across 'Minor' and 'Major' Seizure Types: A Retrospective Analysis of Clinical Outcomes in Pharmacoresistant Epilepsy

Background: Evaluating the differential impact of vagus nerve stimulation (VNS) therapy across various seizure types, our study explores its efficacy specifically in patients with categorized minor and major seizures. Methods: We conducted a retrospective cohort study involving 76 patients with pharmacoresistant epilepsy treated at the University Emergency Hospital of Bucharest between 2021 and 2024. Seizures were classified as 'minor' (including focal-aware and non-motor/absence seizures) and 'major' (including focal to bilateral tonic-clonic and generalized motor seizures), based on modified International League Against Epilepsy (ILAE) criteria. This classification allowed us to assess the response to VNS therapy, defined by a 50% or greater reduction in seizure frequency at the 12-month follow-up. Results: Our findings reveal that major seizures respond more favorably to VNS therapy, significantly reducing both frequency and intensity. In contrast, minor seizures showed a less pronounced response in frequency reduction but noted improvements in neurocognitive functions, suggesting a nuanced benefit of VNS in these cases. Conclusion: The study underscores the importance of seizure type in determining the efficacy of VNS therapy, advocating for personalized treatment approaches based on seizure classification. This approach could potentially enhance clinical outcomes by tailoring VNS settings to specific seizure types, improving overall management strategies in pharmacoresistant epilepsy.

Vagus Nerve Stimulation for Drug Resistant Epilepsy: Clinical Outcome, Adverse Events, and Potential Prognostic Factors in a Single Center Experience

OBJECTIVE

Vagus nerve stimulation (VNS) has been used for adjunctive treatment in drug resistant epilepsy (DRE) for decades. Nevertheless, information is lacking on possible potential prognostic factors. Our study presents the efficacy and safety of VNS with a focus on prognostic factors in 45 patients with DRE.

METHODS

We retrospectively evaluated the clinical outcome of 45 consecutive patients with DRE undergoing VNS implantation in The First Affiliated Hospital of Anhui Medical University between November 2016 and August 2021. Medical records were aggregated across all patient visits. Cox proportional hazards regression was used to estimate the prognostic factors.

RESULTS

Significant decrease in seizure frequency was observed after intermittent stimulation of the vagus nerve. According to the modified McHugh classification, 11 patients (24.4%) were Class I, 11 patients (24.4%) were Class II, four patients (8.9%) were Class III, 10 patients (22.2%) were Class IV, and nine patients (20.0%) were Class V. Notably, 22 patients (48.9%) were responders and four patients (8.9%) were seizure-free at the final follow-up. No significant prognostic factors were found in this cohort. Furthermore, 37 patients reported improved quality of life. Of the patients, 22 (48.9%) experienced adverse events after surgery; hoarseness, discomfort at the surgical site, and coughing were the most common.

CONCLUSION

The results confirmed the efficacy and safety of VNS. No prognostic factors were identified.

Neurostimulation in People with Drug-Resistant Epilepsy: Systematic Review and Meta-Analysis from the ILAE Surgical Therapies Commission

OBJECTIVE

Summarize the current evidence on efficacy and tolerability of vagus nerve stimulation (VNS), responsive neurostimulation (RNS), and deep brain stimulation (DBS) through a systematic review and meta-analysis.

METHODS

We followed the PRISMA reporting standards and searched Ovid Medline, Ovid Embase, and the Cochrane Central Register of Controlled Trials. We included published randomized controlled trials (RCT) and their corresponding open-label extension studies, as well as prospective case series, with ≥ 20 participants (excluding studies limited to children). Our primary outcome was the mean (or median when unavailable) percentage decrease in frequency, as compared to baseline, of all epileptic seizures at last follow-up. Secondary outcomes included proportion of treatment responders and proportion with seizure freedom.

RESULTS

We identified 30 eligible studies, six of which were RCTs. At long-term follow-up (mean 1.3 years), five observational studies for VNS reported a pooled mean percentage decrease in seizure frequency of 34.7% (95% CI: -5.1, 74.5). In the open-label extension studies for RNS, the median seizure reduction was 53%, 66%, and 75% at two, five, and nine years of follow-up, respectively. For DBS, the median reduction was 56%, 65%, and 75% at two, five, and seven years, respectively. The proportion of individuals with seizure freedom at last follow-up increased significantly over time for DBS and RNS while a positive trend was observed for VNS. Quality of life was improved in all modalities. The most common complications included hoarseness, cough and throat pain for VNS and implant site pain, headache, and dysesthesia for DBS and RNS.

SIGNIFICANCE

Neurostimulation modalities are an effective treatment option for drug resistant epilepsy, with improving outcomes over time and few major complications. Seizure reduction rates among the three therapies were similar during the initial blinded phase. Recent long-term follow-up studies are encouraging for RNS and DBS but are lacking for VNS.

Short- and Long-Term Response of Vagus Nerve Stimulation Therapy in Drug-Resistant Epilepsy: A Systematic Review and Meta-Analysis

OBJECTIVES

To compare the short- and long-term efficacies as well as tolerability of vagus nerve stimulation (VNS) for the patients with drug-resistant epilepsy (DRE) in comparison with status at baseline.

MATERIALS AND METHODS

We conducted a specific and systematic search in online data bases for relevant literature published prior to December 2020. The literature retrieved, including randomized clinical trials (RCTs) and observational studies, were then reviewed, and analyzed. A fixed-effect model was used to evaluate the pooled odds ratio (OR) of responder rates and complications associated with RCTs. A random-effect model was used to generate overall responder rates and overall incidences of complication.

RESULTS

A total of 61 studies, featuring 5223 patients, were included in our study. The pooled ORs of responder rates, hoarseness/voice change, throat pain, coughing, dyspnea, paresthesia, muscle pain, and headache during the short-term phase were 2.195 (p = 0.001), 5.527 (p = 0.0001), 0.935 (p = 0.883), 1.119 (p = 0.655), 2.901 (p = 0.005), 1.775 (p = 0.061), 3.606 (p = 0.123), and 0.928 (p = 0.806), respectively. The overall responder rates in 3, 6, 12, 24, 36, 48, and 60 months postoperatively were 0.421, 0.455, 0.401, 0.451, 0.482, 0.502, and 0.508, respectively. The overall incidences of complication were 0.274 for hoarseness/voice change, 0.099 for throat pain, 0.133 for coughing, 0.099 for dyspnea, 0.102 for paresthesia, 0.062 for muscle pain, 0.101 for headache, 0.015 for dysphagia, 0.013 for neck pain, 0.040 for infection, 0.030 for lead fracture, 0.019 for vocal cord palsy, and 0.020 for device malfunction, respectively.

CONCLUSIONS

The estimating of efficacy and tolerability, using data from the existing literature, indicated VNS therapy is a safe and effective treatment option for patients with DRE.

The cerebellum and epilepsy

Epilepsy is the fourth most common neurological disorder, but current treatment options provide limited efficacy and carry the potential for problematic adverse effects. There is an immense need to develop new therapeutic interventions in epilepsy, and targeting areas outside the seizure focus for neuromodulation has shown therapeutic value. While not traditionally associated with epilepsy, anatomical, clinical, and electrophysiological studies suggest the cerebellum can play a role in seizure networks, and importantly, may be a potential therapeutic target for seizure control. However, previous interventions targeting the cerebellum in both preclinical and clinical studies have produced mixed effects on seizures. These inconsistent results may be due in part to the lack of specificity inherent with open-loop electrical stimulation interventions. More recent studies, using more targeted closed-loop optogenetic approaches, suggest the possibility of robust seizure inhibition via cerebellar modulation for a range of seizure types. Therefore, while the mechanisms of cerebellar inhibition of seizures have yet to be fully elucidated, the cerebellum should be thoroughly revisited as a potential target for therapeutic intervention in epilepsy. This article is part of the Special Issue "NEWroscience 2018.

Does One Week of Postoperative Antibiotic Prophylaxis Reduce the Rate of Infection After Vagus Nerve Stimulator Surgery?

OBJECTIVE

Vagus nerve stimulation (VNS) therapy is an increasingly popular treatment for medically intractable epilepsy. During a review of our cases, we noted that one of the senior authors give patients 1 week of antibiotic prophylaxis after VNS surgery while the other does not. We reviewed our experience with postoperative antibiotic prophylaxis after VNS surgery.

METHODS

We retrospectively reviewed the records of patients from January 2009 to September 2018 who had undergone surgery for VNS therapy, including generator replacement. The office and operative notes were reviewed to obtain the indications and operative details for VNS placement.

RESULTS

A total of 570 operations were reviewed, 232 of which were primary implantations and 338 were revisions. The indication was intractable epilepsy in all cases. A total of 5 infections occurred, 4 in the group with postoperative antibiotic prophylaxis and 1 in the group without. The difference was not statistically significant.

CONCLUSION

Just as with any hardware implantation, infection of the hardware can lead to significant morbidity. However, the use of postoperative oral antibiotic prophylaxis did not show benefit in reducing the infection rate.

Prevalence and Incidence of Drug-Resistant Temporal Lobe Epilepsy in Qatar

Background:

Information on the epidemiology of temporal lobe epilepsy associated with hippocampal sclerosis (TLE-HS) from Qatar and the developing countries is scarce. To acquire knowledge on the incidence and prevalence of drug-resistant TLE-HS in Qatar, we designed this analytical and extrapolative systematic review of the existing literature.

Material and methods:

We searched the electronic database PubMed from 1947 until April, 2018, using the following search terms in the title: “epilepsy” OR “temporal lobe” OR “hippocampal sclerosis” AND “epidemiology” OR “incidence” OR “prevalence.” Relevant original studies, reviews, and their references, were included. We extrapolated from the previous international literature to estimate the epidemiology of drug-resistant TLE-HS in Qatar.

Results:

The estimated Qatar incidence of epilepsy varies from 50 to 61 per 100 000 persons per year, and the estimated prevalence of epilepsy is 6.54 per 1000 population; the estimated incidence of TLE varies from 9.5 to 11.6 patients per 100 000 population per year and the estimated prevalence of TLE is 1.76 patients per 1000 people, with 4721 patients having TLE in Qatar. Finally, the reviewed studies also helped in making an estimate of the Qatar prevalence of drug-resistant TLE-HS to be between 0.3 and 0.6 cases per 1000 people (804-1609 current patients) and the Qatar incidence of drug-resistant TLE-HS (2.3-4.3 cases per 100 000 people, per year) with 62 to 116 new patients per year.

Conclusion:

Our study suggests that 804 to 1609 current patients (with 62-116 additional patients per year) in Qatar are suffering from drug-resistant TLE-HS; emphasis should be placed on the surgical aspect of the current Qatar Comprehensive Epilepsy Program.

Dexmedetomidine-Mediated Prevention of Renal Ischemia-Reperfusion Injury Depends in Part on Cholinergic Anti-Inflammatory Mechanisms

BACKGROUND

Organ ischemia-reperfusion injury often induces local and systemic inflammatory responses, which in turn worsen organ injury. These inflammatory responses can be regulated by the central nervous system, particularly by the vagal nerve and nicotinic acetylcholine receptors, which are the key components of cholinergic anti-inflammatory pathway. Activation of the cholinergic anti-inflammatory pathway can suppress excessive inflammatory responses and be a potential strategy for prevention of ischemia-reperfusion injury of organs including the kidney.

METHODS

Vagal nerve activity, plasma acetylcholine, catecholamine and inflammatory mediators, renal tissue injury, and cell death were measured in mice with bilateral renal ischemia/reperfusion with or without treatment with dexmedetomidine (Dex), an α2-adrenergic receptor agonist.

RESULTS

Dex significantly increased the discharge frequency of the cervical vagal nerve by up to 142 Hz (mean) (P < .001), and preserved kidney gross morphology and structure and attenuated cell apoptosis after ischemia-reperfusion. Furthermore, Dex also significantly increased acetylcholine release to 135.8 pmol/L (median) when compared to that (84.7 pmol/L) in the sham group (P < .001) and reduced the levels of several inflammatory mediators induced by renal ischemia/reperfusion. All the effects were abolished by vagotomy, splenectomy, or combinative administration of atipamezole, an α2-adrenergic receptor antagonist.

CONCLUSIONS

Our findings suggest that Dex provides renoprotection, at least in part, through anti-inflammatory effects of the parasympathetic nervous system activation in addition to its direct actions on α2-adrenergic receptors.

Excitation, but not inhibition, of the fastigial nucleus provides powerful control over temporal lobe seizures

KEY POINTS

On-demand optogenetic inhibition of glutamatergic neurons in the fastigial nucleus of the cerebellum does not alter hippocampal seizures in a mouse model of temporal lobe epilepsy. In contrast, on-demand optogenetic excitation of glutamatergic neurons in the fastigial nucleus successfully inhibits hippocampal seizures. With this approach, even a single 50 ms pulse of light is able to significantly inhibit seizures. On-demand optogenetic excitation of glutamatergic fastigial neurons either ipsilateral or contralateral to the seizure focus is able to inhibit seizures. Selective excitation of glutamatergic nuclear neurons provides greater seizure inhibition than broadly exciting nuclear neurons without cell-type specificity.

ABSTRACT

Temporal lobe epilepsy is the most common form of epilepsy in adults, but current treatment options provide limited efficacy, leaving as many as one-third of patients with uncontrolled seizures. Recently, attention has shifted towards more closed-loop therapies for seizure control, and on-demand optogenetic modulation of the cerebellar cortex was shown to be highly effective at attenuating hippocampal seizures. Intriguingly, both optogenetic excitation and inhibition of cerebellar cortical output neurons, Purkinje cells, attenuated seizures. The mechanisms by which the cerebellum impacts seizures, however, are unknown. In the present study, we targeted the immediate downstream projection of vermal Purkinje cells - the fastigial nucleus - in order to determine whether increases and/or decreases in fastigial output can underlie seizure cessation. Though Purkinje cell input to fastigial neurons is inhibitory, direct optogenetic inhibition of the fastigial nucleus had no effect on seizure duration. Conversely, however, fastigial excitation robustly attenuated hippocampal seizures. Seizure cessation was achieved at multiple stimulation frequencies, regardless of laterality relative to seizure focus, and even with single light pulses. Seizure inhibition was greater when selectively targeting glutamatergic fastigial neurons than when an approach that lacked cell-type specificity was used. Together, these results suggest that stimulating excitatory neurons in the fastigial nucleus may be a promising approach for therapeutic intervention in temporal lobe epilepsy.

Surgical outcomes for medically intractable epilepsy in low- and middle-income countries: a systematic review and meta-analysis

OBJECTIVE

The aim of this study was to describe the current state of epilepsy surgery and establish estimates of seizure outcomes following surgery for medically intractable epilepsy (MIE) in low- and middle-income countries (LMICs).

METHODS

The MEDLINE and Embase databases were searched without publication date restriction. This search was supplemented by a manual screen of key epilepsy and neurosurgical journals (January 2005 to December 2016). Studies that reported outcomes for at least 10 patients of any age undergoing surgery for MIE in LMICs over a defined follow-up period were included. A meta-analysis with a random-effects model was performed in accordance with the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement and MOOSE (Meta-analysis of Observational Studies in Epidemiology) guidelines. Pooled estimates of seizure freedom and favorable seizure outcomes following anterior temporal lobectomy with or without amygdalohippocampectomy (ATL ± AH) were reported.

RESULTS

Twenty studies were selected, of which 16 were from Asian centers. The average age at surgery in all studies was less than 30 years, and the average preoperative duration of epilepsy ranged from 3 to 16.1 years. Mesial temporal sclerosis accounted for 437 of 951 described pathologies, and 1294 of the 1773 procedures were ATL ± AH. Based on 7 studies (646 patients) the pooled seizure freedom estimate following ATL ± AH was 68% (95% CI 55%-82%). Based on 8 studies (1096 patients), the pooled estimate for favorable seizure outcomes was 79% (95% CI 74%-85%).

CONCLUSIONS

Surgery for MIE in LMICs shows a high percentage of seizure freedom and favorable outcomes. These findings call for a concerted global effort to improve timely access to surgery for MIE patients in these regions, including investments aimed at refining existing and establishing additional centers.

Effect of vagus nerve stimulation on blood glucose concentration in epilepsy patients - Importance of stimulation parameters

In previous animal experiments, we demonstrated that cervical vagus nerve stimulation (VNS) inhibits pancreatic insulin secretion, thereby raises blood glucose levels, and impairs glucose tolerance through afferent signaling. However, there are no reports suggesting that similar effects occur in patients treated with chronic cervical VNS for epilepsy. In contrast to clinical VNS used for epilepsy, where the stimulation is intermittent with cycles of on and off periods, stimulation was continuous in our previous animal experiments. Thus, we hypothesized that the timing of the stimulation on/off cycles is critical to prevent impaired glucose tolerance in epilepsy patients chronically treated with cervical VNS. We conducted a retrospective analysis of medical records from patients with epilepsy. Blood glucose levels did not differ between patients treated with pharmacotherapy only (98 ± 4 mg/dL, n = 16) and patients treated with VNS plus pharmacotherapy (99 ± 3 mg/dL, n = 24, duration of VNS 4.5 ± 0.5 years). However, a multiple linear correlation analysis of patients with VNS demonstrated that during the follow‐up period of 7.9 ± 0.7 years, blood glucose levels increased in patients with long on and short off periods, whereas blood glucose did not change or even decreased in patients that were stimulated with short on and long off periods. We conclude that chronic cervical VNS in patients with epilepsy is unlikely to induce glucose intolerance or hyperglycemia with commonly used stimulation parameters. However, stimulation on times of longer than 25 sec may bear a risk for hyperglycemia, especially if the stimulation off time is shorter than 200 sec.

Efficacy and tolerability of vagus nerve stimulation therapy (VNS) in Slovenian epilepsy patients: younger age and shorter duration of epilepsy might result in better outcome

To review the outcome of vagus nerve stimulation (VNS) therapy in all implanted Slovenian patients with drug-resistant epilepsy, data on 48 patients implanted between 2001 and 2015 were obtained retrospectively from medical records. The outcome was assessed in 2016. Out of 48 patients, 39 responded at follow up. The seizure frequency was reduced in 18 (46.2%) patients; 13 (33.3%) of them reported ≥50% reduction after 12 months of therapy. The responder rate was higher among patients implanted before the age of six years. Ictal severity decreased in 22 (56.4%), seizure duration in 19 (48.7%) and post-ictal recovery time in 22 (56.4%) patients. Favorable effects on the quality of life (QOL) were improved alertness in 33.3%, concentration in 41.0%, energy and mood in 38.5%, and memory in 17.9% of patients. Reduced seizure burden and improved QOL were more often observed in patients implanted at a younger age. Shorter duration of epilepsy was significantly associated with QOL improvement. Adverse effects were transient. Overall positive effects showed VNS to be a safe, well-tolerated and effective adjunctive treatment in most severe drug-resistant epilepsy patients. Implantation at a younger age and shorter duration of epilepsy before implantation could be important predictors of better outcome.

Epilepsy surgery in low- and middle-income countries: A scoping review

BACKGROUND

Epilepsy surgery is an important treatment option for people with drug-resistant epilepsy. Surgical procedures for epilepsy are underutilized worldwide, but it is far worse in low- and middle-income countries (LMIC), and it is less clear as to what extent people with drug-resistant epilepsy receive such treatment at all. Here, we review the existing evidence for the availability and outcome of epilepsy surgery in LMIC and discuss some challenges and priority.

METHODS

We used an accepted six-stage methodological framework for scoping reviews as a guide. We searched PubMed, Embase, Global Health Archives, Index Medicus for South East Asia Region (IMSEAR), Index Medicus for Eastern Mediterranean Region (IMEMR), Latin American & Caribbean Health Sciences Literature (LILACS), African Journal Online (AJOL), and African Index Medicus (AIM) to identify the relevant literature.

RESULTS

We retrieved 148 articles on epilepsy surgery from 31 countries representing 22% of the 143 LMIC. Epilepsy surgery appears established in some of these centers in Asia and Latin America while some are in their embryonic stage reporting procedures in a small cohort performed mostly by motivated neurosurgeons. The commonest surgical procedure reported was temporal lobectomies. The postoperative seizure-free rates and quality of life (QOL) are comparable with those in the high-income countries (HIC). Some models have shown that epilepsy surgery can be performed within a resource-limited setting through collaboration with international partners and through the use of information and communications technology (ICT). The cost of surgery is a fraction of what is available in HIC.

CONCLUSION

This review has demonstrated the availability of epilepsy surgery in a few LMIC. The information available is inadequate to make any reasonable conclusion of its existence as routine practice. Collaborations with international partners can provide an opportunity to bring high-quality academic training and technological transfer directly to surgeons working in these regions and should be encouraged.

Drug-Resistant Epilepsy and Surgery

BACKGROUND

Epilepsy is a chronic brain disease that is caused by various factors and characterized by recurrent, episodic and temporary central nervous system dysfunction which results due to excessive discharge of brain neurons. In the past decades, despite the continuous development of antiepileptic drugs, there are still many patients with epilepsy progressing to drugresistant epilepsy. Currently, surgical treatment is one of important way to cure drug-resistant epilepsy.

METHODS

Data were collected from Web of Science, Medline, Pubmed, through searching of these keywords: "surgery" and "drug-resistant epilepsy".

RESULTS

An increasing number of studies have shown that surgery plays an important role in the treatment of drug-resistant epilepsy. Moreover, the comprehensive treatment mainly based on surgery can achieve the remission and even cure of drug-resistant epilepsy.

CONCLUSION

In this review, we discuss the pathogenesis of drug-resistant epilepsy and the comprehensive treatment mainly based on surgery; this review may provide a reference for the clinical treatment of drug-resistant epilepsy.

The role of vagus nerve stimulation in refractory epilepsy

ABSTRACT Vagus nerve stimulation is an adjunctive therapy used to treat patients with refractory epilepsy who are not candidates for resective surgery or had poor results after surgical procedures. Its mechanism of action is not yet fully comprehended but it possibly involves modulation of the locus coeruleus, thalamus and limbic circuit through noradrenergic and serotonergic projections. There is sufficient evidence to support its use in patients with focal epilepsy and other seizure types. However, it should be recognized that improvement is not immediate and increases over time. The majority of adverse events is stimulation-related, temporary and decreases after adjustment of settings. Future perspectives to improve efficacy and reduce side effects, such as different approaches to increase battery life, transcutaneous stimulation and identification of prognostic factors, should be further investigated.