Impact of Cardiac-Based Vagus Nerve Stimulation Closed-Loop Stimulation on the Seizure Outcome of Patients With Generalized Epilepsy: A Prospective,Individual-Control Study

ObjectivesWe designed a prospective, individual-controlled study to evaluate the effect of cardiac-based VNS (cbVNS) in a cohort of patients with generalized epilepsy (GE).Materials and MethodsTwenty patients were included. They were followed up for six months under regular VNS (rVNS) and subsequently for six months during cbVNS. Stimulation parameters were 500 μsec, 30 Hz, and up to 2.5 mA. Seizure frequency was documented after two, four, and six months during the rVNS and cbVNS phases. Patients with at least 50% seizure frequency reduction were considered responders. The total and relative amount of stimulation cycles generated by both rVNS and cbVNS activation were documented. Findings during rVNS were compared to baseline and cbVNS data were compared to those during rVNS.ResultsThere was a significant decrease in mean seizure frequency (61% [95% CI, 48-74]; p < 0.001) during the rVNS phase compared to baseline. There was no additional significant (16% [95% CI, 4-35]; p = 0.097) mean seizure frequency reduction during cbVNS compared to the rVNS phase. Fifteen patients (75%) were considered responders after rVNS. Four patients (20%) were considered responders after six months of cbVNS. During the cbVNS phase, the mean total number of cycles/day was 346, 354, and 333 for months two, four, and six, respectively; the cycles generated by rVNS were 142, 138, and 146 for months two, four, and six, respectively; and cycles generated by cbVNS were 204, 215, and 186 for months two, four, and six, respectively. There was no relationship between the mean total number of cycles (−6[95% CI, −85 to 72]; p = 0.431), the mean number of auto-stimulation cycles (27[95% CI,−112 to 166]; p = 0.139), the mean number of regular cycles (−33[95% CI,−123 to 57]; p = 0.122), or the mean percentage of auto-stimulation cycles (13[95% CI,19- 45]; p = 0.109) and outcome during the cbVNS phase. Eight patients showed some decrease in seizure frequency during cbVNS.ConclusionsrVNS was effective in reducing seizure frequency in patients with generalized epilepsy, but activation of the cbVNS feature did not add significantly to rVNS efficacy. On the other hand, although not statistically significant, 40% of the patients showed some reduction in seizure frequency, which might prove useful at an individual level.     

Update zur Vagusnervstimulation

Despite the use of a large variety of modern anticonvulsants in the management of epileptic seizures, there is a special patient population without measureable profit. This group of patients is amenable to new therapeutic approaches, such as vagus nerve stimulation (VNS) as a non-pharmacological treatment. This article elucidates the importance of VNS in the treatment of epilepsies, illustrates the procedure after implantation (e.g. ramp up and managing different duty cycles), summarizes the results of long-term VNS in different study groups and gives an insight into a new therapy vision. Over the years VNS has become established as an adjunct therapy for treatment of pharmacoresistant epilepsy and offers an innovative approach by a newly developed on demand autostimulation for the treatment of seizures.     

VNS parameters for clinical response in Epilepsy

BackgroundWhile vagus nerve stimulation (VNS) has been in use for over two decades, little professional guidance exists to describe dosing and titration of therapy which is the consequence of a limited amount of evidence developed during the pre-market phase of therapy development. Post-market surveillance of dosing practice has revealed significant deviations from dosing and titration guidance offered by professional societies as well as the manufacturer.ObjectiveThis analysis aims to identify a target dose for VNS Therapy in Epilepsy.MethodsHerein, VNS clinical outcomes are linked to the patient-specific dosing parameters for each study visit (n = 1178 patients). A generalized linear mixed model was built to ascertain the relationship between key stimulation parameters (i.e., Output Current, Pulse Width, Signal Frequency, and Duty Cycle) and clinical response, defined as a 50% or greater reduction in seizure frequency from baseline. Other demographic parameters of interest, such as duration of epilepsy and age at implant, were also explored.ResultsA population level target output current and duty cycle for VNS therapy for epilepsy was identified as 1.61 mA and 17.1% duty cycle. Patients with shorter duration of epilepsy were identified to have a higher likelihood to respond to VNS therapy (p < 0.001). While patients who were on the therapy longer were more likely to respond to the therapy, the effect did not interact with the dosing settings - suggesting that patients who have been chronically underdosed may still benefit from achieving the target dose.ConclusionAn opportunity exists to improve upon VNS outcomes by aligning clinical practice around this evidence-based target dose.     

Long-term results of vagal nerve stimulation for adults with medication-resistant epilepsy who have been on unchanged antiepileptic medication

PurposeSeveral studies suggest that vagal nerve stimulation (VNS) is an effective treatment for medication-resistant epileptic patients, although patients’ medication was usually modified during the assessment period. The purpose of this prospective study was to evaluate the long-term effects of VNS, at 18 months of follow-up, on epileptic patients who have been on unchanged antiepileptic medication.MethodsForty-three patients underwent a complete epilepsy preoperative evaluation protocol, and were selected for VNS implantation. After surgery, patients were evaluated on a monthly basis, increasing stimulation 0.25 mA at each visit, up to 2.5 mA. Medication was unchanged for at least 18 months since the stimulation was started. The outcome was analysed in relation to patients’ clinical features, stimulation parameters, epilepsy type, magnetic resonance imaging (MRI) results, and history of prior brain surgery.ResultsOf the 43 operated patients, 63% had a similar or greater than 50% reduction in their seizure frequency. Differences in the responder rate according to stimulation intensity, age at onset of epilepsy, duration of epilepsy before surgery, previous epilepsy surgery and seizure type, did not reach statistical significance. Most side effects were well tolerated.Conclusions62.8% of our series of 43 medication-resistant epileptic patients experienced a significant long-term seizure reduction after VNS, even in a situation of on unchanged medical therapy. Patient characteristics predictive of VNS responsiveness remain subject to investigation. Controlled studies with larger sample sizes, on VNS for patients with medication-resistant epilepsy on unchanged medication, are necessary to confirm VNS efficacy for drug-resistant epilepsy, and to identify predictive factors.     

Laryngeal Muscle-Evoked Potential Recording as an Indicator of Vagal Nerve Fiber Activation

BackgroundVagus nerve stimulation (VNS) is an adjunctive therapy for drug-resistant epilepsy. Noninvasive evoked potential recordings in laryngeal muscles (LMEPs) innervated by vagal branches may provide a marker to assess effective vagal nerve fiber activation. We investigated VNS-induced LMEPs in patients with epilepsy in acute and chronic settings.Materials and MethodsA total of 17 of 25 patients underwent LMEP recordings at initiation of therapy (acute group); 15 of 25 patients after one year of VNS (chronic group); and 7 of 25 patients were tested at both time points (acute + chronic group). VNS-induced LMEPs were recorded following different pulse widths and output currents using six surface laryngeal EMG electrodes to calculate input/output curves and estimate LMEP latency, threshold current for minimal (I_threshold), half-maximal (I₅₀), and 95% of maximal (I₉₅) response induction and amplitude of maximal response (V_max). These were compared with the acute + chronic group and between responders and nonresponders in the acute and chronic group.ResultsVNS-induced LMEPs were present in all patients. I_threshold and I₉₅ values ranged from 0.25 to 1.00 mA and from 0.42 to 1.77 mA, respectively. Estimated mean LMEP latencies were 10 ± 0.1 milliseconds. No significant differences between responders and nonresponders were observed. In the acute + chronic group, I_threshold values remained stable over time. However, at the individual level in this group, V_max was lower in all patients after one year compared with baseline.ConclusionsNoninvasive VNS-induced LMEP recording is feasible both at initiation of VNS therapy and after one year. Low output currents (0.25–1.00 mA) may be sufficient to activate vagal Aα-motor fibers. Maximal LMEP amplitudes seemed to decrease after chronic VNS therapy in patients.     

Vagus Nerve Stimulation and Atrial Fibrillation: Revealing the Paradox

Background and ObjectiveThe cardiac autonomic nervous system (CANS) plays an important role in the pathophysiology of atrial fibrillation (AF). Cardiovascular disease can cause an imbalance within the CANS, which may contribute to the initiation and maintenance of AF. Increased understanding of neuromodulation of the CANS has resulted in novel emerging therapies to treat cardiac arrhythmias by targeting different circuits of the CANS. Regarding AF, neuromodulation therapies targeting the vagus nerve have yielded promising outcomes. However, targeting the vagus nerve can be both pro-arrhythmogenic and anti-arrhythmogenic. Currently, these opposing effects of vagus nerve stimulation (VNS) have not been clearly described. The aim of this review is therefore to discuss both pro-arrhythmogenic and anti-arrhythmogenic effects of VNS and recent advances in clinical practice and to provide future perspectives for VNS to treat AF.Materials and MethodsA comprehensive review of current literature on VNS and its pro-arrhythmogenic and anti-arrhythmogenic effects on atrial tissue was performed. Both experimental and clinical studies are reviewed and discussed separately.ResultsVNS exhibits both pro-arrhythmogenic and anti-arrhythmogenic effects. The anatomical site and stimulation settings during VNS play a crucial role in determining its effect on cardiac electrophysiology. Since the last decade, there is accumulating evidence from experimental studies and randomized clinical studies that low-level VNS (LLVNS), below the bradycardia threshold, is an effective treatment for AF.ConclusionLLVNS is a promising novel therapeutic modality to treat AF and further research will further elucidate the underlying anti-arrhythmogenic mechanisms, optimal stimulation settings, and site to apply LLVNS.     

Regional brain perfusion changes during standard and microburst vagus nerve stimulation in dogs

PurposeVagus nerve stimulation (VNS) is an effective adjunctive treatment for refractory epilepsy in humans, but its mechanism of action (MOA) and optimal stimulation parameters are still unknown. Functional neuroimaging studies could provide better insight into the brain structures involved in the activity of VNS, but have not yet been described in dogs. The aim of this study was to investigate the effect of acute VNS on the regional cerebral blood flow (rCBF) in dogs using micro-SPECT (μ-SPECT). Additionally, a novel stimulation paradigm (microburst VNS) was used and compared with standard VNS.MethodsA VNS Therapy^® System was implanted in ten Beagle dogs. μ-SPECT was performed after sham, standard and microburst VNS in a randomized, cross-over study. Nineteen volumes of interest (VOIs) were semi-quantitatively analysed and perfusion indices (PIs) were calculated. Furthermore, a rostro-caudal gradient (R-C), an asymmetry index (AI) and a cortical-subcortical index (Co-SCo) were determined. The SPECT results after standard and microburst VNS were compared pairwise with sham stimulation.ResultsAcute standard VNS did not cause significant rCBF alterations. Acute microburst VNS caused a significant hypoperfusion in the left frontal lobe (P = 0.023) and in the right parietal lobe (P = 0.035). Both stimulation paradigms did not cause changes in R-C, AI nor Co-SCo.ConclusionsMicroburst VNS is more potent than standard VNS to modulate the rCBF in the dog. Our results promote further research towards the antiepileptic effect of microburst VNS in dogs and humans.     

Vagus nerve stimulation in children with drug‐resistant epilepsy: age at implantation and shorter duration of epilepsy as predictors of better efficacy?

Aim. To study the efficacy of vagus nerve stimulation (VNS) therapy in a highly drug‐resistant childhood epilepsy patient group and to investigate the effect of age at implantation on efficacy. Methods. The efficacy of VNS treatment was analysed in a cohort of 70 patients with drug‐resistant epilepsy. Both children with focal (n=16) and generalized epilepsies (n=54) were included. Age at implantation varied between 19 months and 25 years. Results. Overall, responder rate was 54% with 5.7% children becoming seizure‐free. The only factor in our analysis that could predict good outcome was age at implantation. In the youngest group (<5 years), the responder rate was 77% and this group also included three of the four seizure‐free children. These three seizure‐free children were known to have tuberous sclerosis. There were no outcome differences between generalized and focal epilepsies. Conclusions. Our single centre study confirms previous studies on the efficacy of VNS in children. A larger study using multivariate analysis to disentangle the contribution of different factors (such as age at implantation, aetiology, and epilepsy duration) is necessary to confirm our preliminary finding that younger age at VNS implantation might result in a better outcome.     

Efficacy of vagus nerve stimulation as a treatment for medically intractable epilepsy in brain tumor patients. A case-controlled study using the VNS therapy Patient Outcome Registry

PurposeVagus nerve stimulation (VNS) therapy is a procedure to control seizure frequency in patients with medically intractable epilepsy. However, there is no data on efficacy in the subset of these patients with brain tumors. The purpose of this study is to evaluate the efficacy of VNS therapy in patients with brain tumor-associated medically intractable epilepsy.MethodsData from the VNS therapy Patient Outcome Registry, maintained by the manufacturer of the device, Cyberonics Inc. (Houston, TX, USA), was queried to characterize the response of patients in whom a brain tumor was listed as the etiology of epilepsy. A case–control analysis was implemented and patient outcome was measured by Engel classification, median seizure response and responder rate (≥50% seizure reduction) using t-tests and chi-squared tests.ResultsIn 107 patients with an epilepsy etiology related to a brain tumor, seizure reduction was 45% at 3 months and 79% at 24 months with a responder rate of 48% at 3 months and 79% at 24 months. There was no statistical difference in seizure reduction compared with 326 case–control patients from the registry without brain tumors. There was no significant difference in anti-epileptic drug (AED) usage from baseline to 24 months post implant in either group.ConclusionsVNS therapy is equally effective in patients who suffer seizures secondary to brain tumors as in patients without history of a brain tumor. VNS therapy is a viable treatment option for patients with brain tumor associated medically intractable epilepsy, assuming cytoreductive and other adjuvant therapies have been fully explored.     

Vagusnervstimulation bei epileptischen Enzephalopathien

Epileptic encephalopathies encompass a heterogeneous group of childhood epilepsies with poor prognosis, and treatment is a special challenge considering the possible impairments in neurocognitive development. Early diagnosis and successful treatment are, therefore, crucial for this patient group. Four patients with progressive epilepsies, who responded outstandingly well to vagus nerve stimulation (VNS), are presented. The epilepsies of all patients were drug-resistant and surgical treatment was not an option. VNS, not as a first-line therapy but considered early after delineation of a progressive epilepsy course, represents an important therapeutic option in patients with epileptic encephalopathies.     

Mode of vagus nerve stimulation differentially affects sleep related breathing in patients with epilepsy

PurposeWe describe the influence of vagus nerve stimulation (VNS) with standard mode and rapid cycling mode on sleep related breathing in two patients with epilepsy.MethodsTwo VNS treated patients underwent digital video-polysomnography for three nights (night 1: rapid cycling mode; night 2: standard mode; night 3: off mode).ResultsIn patient 1, on off mode, apnea-hypopnea index (AHI) was 11.1/h, respiratory effort-related arousal index (RERAI) 0.9/h, flow limitation index (FLI) 0.9/h and oxygen desaturation index (ODI) 10.2/h. On standard mode, AHI was 5.5/h, RERAI 1.7/h, FLI 4.1/h and ODI 5.5/h. On rapid cycling mode, AHI was 10.4/h, RERAI 7.9/h, FLI 17.3/h and ODI 10.3/h. In patient 2, on off mode, AHI was 1.6/h, RERAI 0.8/h, FLI 2.2/h and ODI 0/h. On standard mode, AHI was 2.9/h, RERAI 2.4/h, FLI 2.6/h and ODI 2.9/h. On rapid cycling mode, AHI was 0.7/h, RERAI increased to 15.4/h, FLI to 52.0/h and ODI was 0.7/h.ConclusionsThe number of RERAs as well as the number of flow limitations were higher with the rapid cycling mode compared to standard mode and stimulation off and might be related to the higher impulse frequency.     

A Comprehensive Review of Vagus Nerve Stimulation for Depression

ObjectivesVagus nerve stimulation (VNS) is reemerging as an exciting form of brain stimulation, due in part to the development of its noninvasive counterpart transcutaneous auricular VNS. As the field grows, it is important to understand where VNS emerged from, including its history and the studies that were conducted over the past four decades. Here, we offer a comprehensive review of the history of VNS in the treatment of major depression.Materials and MethodsUsing PubMed, we reviewed the history of VNS and aggregated the literature into a narrative review of four key VNS epochs: 1) early invention and development of VNS, 2) path to Food and Drug Administration (FDA) approval for depression, 3) refinement of VNS treatment parameters, and 4) neuroimaging of VNS.ResultsVNS was described in the literature in the early 1900s; however, gained traction in the 1980s as Zabara and colleagues developed an implantable neurocybernetic prosthesis to treat epilepsy. As epilepsy trials proceed in the 1990s, promising mood effects emerged and were studied, ultimately leading to the approval of VNS for depression in 2005. Since then, there have been advances in understanding the mechanism of action. Imaging techniques like functional magnetic resonance imaging and positron emission tomography further aid in understanding direct brain effects of VNS.ConclusionsThe mood effects of VNS were discovered from clinical trials investigating the use of VNS for reducing seizures in epileptic patients. Since then, VNS has gone on to be FDA approved for depression. The field of VNS is growing, and as noninvasive VNS quickly advances, it is important to consider a historical perspective to develop future brain stimulation therapies.     

Invasive Hirnstimulationsverfahren in der Epilepsietherapie

For patients with epilepsy not responding or not being eligible for pharmacological treatment or epilepsy surgery, therapeutic options are limited. Alternative therapeutic options include methods of brain stimulation like vagus nerve stimulation (VNS) or deep brain stimulation (DBS). In recent years, these methods have been subject of considerable research efforts given the unfavorable prognosis of refractory or catastrophic epilepsies. The following review provides a basic introduction into clinical praxis, current knowledge and prospects of invasive stimulation techniques.     

Effect of chronic vagal nerve stimulation on interictal epileptiform discharges

We evaluated the effect of vagus nerve stimulation (VNS) on interictal epileptiform discharges (IEDs) in 32 epileptic patients (18 females; 14 males) with an average age of 42.2 ± 11.4 years, all of whom had been suffering from epilepsy for an average of 29.2 ± 14.5 years. All of the patients had received VNS for 5 years. The first EEG was performed prior to the initiation of stimulation; the second EEG was performed at the 5-year follow-up visit. The duration of each EEG was 30 min. We compared these two EEGs in terms of the number of IEDs present in each patient and correlated them to other variables.The average total number of IEDs during EEG and the total number of seconds in which IEDs were present decreased significantly after 5 years of stimulation from 97.3 ± 106.9 resp. 80.6 ± 86.1 to 49.4 ± 94.0 resp. 37.8 ± 65.0. Although there was no positive correlation between the reduction of IEDs and the percent of seizure reduction, we found a greater decrease of IEDs in patients who responded to VNS in comparison to those who did not. The decrease of IEDs was more pronounced in patients suffering from temporal lobe epilepsy than in patients suffering from extratemporal epilepsy. No other significant correlations were found.VNS reduced IEDs in patients chronically simulated for epilepsy. The reduction of IEDs was greater in patients who responded to VNS and in patients suffering from temporal lobe epilepsy.     

Vagal Nerve Stimulation: A Bibliometric Analysis of Current Research Trends

BackgroundVagal nerve stimulation (VNS) has become established as an effective tool for the management of various neurologic disorders. Consequently, a growing number of VNS studies have been published over the past four decades. This study presents a bibliometric analysis investigating the current trends in VNS literature.Materials and MethodsUsing the Web of Science collection data base, a search was performed to identify literature that discussed applications of VNS from 2000 to 2021. Analysis and visualization of the included literature were completed with VOSviewer.ResultsA total of 2895 publications were identified. The number of articles published in this area has increased over the past two decades, with the most citations (7098) occurring in 2021 and the most publications (270) in 2020. The h-index, i-10, and i-100 were 97, 994, and 91, respectively, with 17.0 citations per publication on average. The highest-producing country and institution of VNS literature were the United States and the University of Texas, respectively. The most productive journal was Epilepsia. Epilepsy was the predominant focus of VNS research, with the keyword “epilepsy” having the greatest total link strength (749) in the keyword analysis. The keyword analysis also revealed two major avenues of VNS research: 1) the mechanisms by which VNS modulates neural circuitry, and 2) therapeutic applications of VNS in a variety of diseases beyond neurology. It also showed a significant prevalence of noninvasive VNS research. Although epilepsy research appears more linked to implanted VNS, headache and depression specialists were more closely associated with noninvasive VNS.ConclusionVNS may serve as a promising intervention for rehabilitation beyond neurologic applications, with an expanding base of literature over the past two decades. Although epilepsy researchers have produced most current literature, other fields have begun to explore VNS as a potential treatment, likely owing to the rise of noninvasive forms of VNS.     

Sleep disordered breathing in children receiving vagus nerve stimulation therapy

ObjectiveThe effects of vagus nerve stimulation (VNS) on sleep disordered breathing (SDB) have been reported in limited case series. Detailed studies, particularly in the pediatric population, have not been performed. The primary purpose of this study is to describe clinical characteristics, polysomnographic findings, and management of children treated with VNS.MethodsA retrospective review of medical records and polysomnography data was performed in patients ages 0–20 years old receiving VNS therapy for refractory epilepsy at Cincinnati Children's Hospital Medical Center.Results22 subjects met the inclusion criteria. 50% were male. The mean age at the time of VNS insertion was 8.4 ± 4.0 years. The mean age at the first PSG was 10.6 ± 4.3 years. Common presentations to sleep clinics included snoring (77.3%), frequent nighttime awakening (68.1%), and parasomnias (63.6%). The median apnea-hypopnea index (AHI) was 4.5/hr (IQR 3.0–13.1) and the median obstructive index (OI) was 4.1/hr (1.5–12.8). Obstructive sleep apnea (OSA) was diagnosed after VNS insertion in 19 patients (86.4%), 8 of which (36.3%) had severe OSA. Six patients (27.3%) had significant hypoventilation. For management, 6 patients (27.2%) were treated with bilevel PAP, 3 patients (13.6%) with CPAP, 2 patients (9.1%) with ventilator, 4 patients (18.2%) with upper airway surgeries, and 9 patients (40.9%) received medications only.ConclusionsSDB is common in pediatric patients with medically refractory epilepsy managed with VNS who were referred to sleep medicine clinics. Both OSA and nocturnal alveolar hypoventilation are relatively common in this population. Management of SDB often involves the use of positive airway pressure therapy or upper airway surgeries. Further studies are needed to assess the prevalence, risk factors, and the effect of treatments on epilepsy control. This study highlights the need for screening of SDB prior to and following VNS implantation.     

Effect of Vagus Nerve Stimulation on Attention and Working Memory in Neuropsychiatric Disorders: A Systematic Review

BackgroundIt has been suggested that vagus nerve stimulation (VNS) may enhance attention and working memory. The neuromodulator effects of VNS are thought to activate the release of neurotransmitters involving cognition and to promote neuronal plasticity. Therefore, VNS has been studied for its effects on attention and working memory impairment in neuropsychiatric disorders.ObjectivesThis study aimed to assess the effects of VNS on attention and working memory among patients with neuropsychiatric disorders, examine stimulation parameters, provide mechanistic hypotheses, and propose future studies using VNS.Materials and MethodsWe conducted a systematic review using electronic databases MEDLINE (Ovid), Embase (Ovid), Cochrane library, and PsycINFO (Ovid). Narrative analysis was used to describe the therapeutic effects of VNS on attention and working memory, describe stimulation parameters, and propose explanatory mechanisms.ResultsWe identified 20 studies reporting VNS effects on attention and working memory in patients with epilepsy or mood disorders. For epilepsy, there was one randomized controlled trial from all 18 studies. It demonstrated no statistically significant differences in the cognitive tasks between active and control VNS. From a within-subject experimental design, significant improvement of working memory after VNS was demonstrated. One of three nonrandomized controlled trials found significantly improved attentional performance after VNS. The cohort studies compared VNS and surgery and found attentional improvement in both groups. Nine of 12 pretest-posttest studies showed improvement of attention or working memory after VNS. For mood disorders, although one study showed significant improvement of attention following VNS, the other did not.ConclusionsThis review suggests that, although we identified some positive results from eligible studies, there is insufficient good-quality evidence to establish VNS as an effective intervention to enhance attention and working memory in persons with neuropsychiatric disorders. Further studies assessing the efficacy of such intervention are needed.     

Papel de la estimulación del nervio vago en el tratamiento de la epilepsia refractaria. Resultados clínicos e impacto en la calidad de vida

BackgroundVagus nerve stimulation (VNS) is used as a complementary therapy to pharmacological treatment in patients with refractory epilepsy. This study aims to evaluate the efficacy of VNS in reducing seizure frequency, severity, and duration; reducing the number of antiepileptic drugs administered; and improving patients’ quality of life.Material and methodsWe analysed the clinical progression of 70 patients with refractory epilepsy treated with VNS at Hospital Universitario de Alicante and Hospital Clínico de Valencia. Data were collected before and after the procedure. The difference in seizure frequency pre- and post-VNS was classified using the McHugh scale. Data were also collected on seizure duration and severity, the number of drugs administered, and quality of life.ResultsAccording to the McHugh classification, 12.86% of the patients were Class I, 44.29% were Class II, 40% were Class III, and the remaining 2.86% of patients were Class IV-V. A ≥ 50% reduction in seizure frequency was observed in 57.15% of patients. Improvements were observed in seizure duration in 88% of patients and in seizure severity in 68%; the number of drugs administered was reduced in 66% of patients, and 93% reported better quality of life.ConclusionsVNS is effective for reducing seizure frequency, duration, and severity and the number of antiepileptic drugs administered. It also enables an improvement in patients’ quality of life.     

Vagus nerve stimulation for medically refractory absence epilepsy

PurposeA proportion of patients with childhood and juvenile absence epilepsies (CAE, JAE) are likely to be classified as medically refractory. In view of evidence gap for the treatment of such patients, this series is reported to generate estimate for efficacy of vagus nerve stimulation (VNS) in this patient population.MethodsPatients were identified by a chart review of all VNS recipients between January 1, 2006 and December 31, 2011. The diagnosis of CAE and JAE was based on conventional criteria. Details of demography, epilepsy phenomenology, management and outcomes were extracted. The outcome measures included reduction in daily seizure frequency measured as a percentage of pre-VNS seizure frequency and classified on International League Against Epilepsy (ILAE) outcome scale.ResultsNine patients (7 CAE, 2 JAE) with a mean age of seizure onset of 5.4 years (±3.9) were identified. Mean duration of epilepsy prior to VNS implant was found to be 3.9 years (±1.4). These patients had failed a median of 5 anti-epileptic drugs before being referred for consideration of surgical treatment. After a mean follow-up of 33.9 months (±25.5, minimum 4 months), 1 patient attained complete seizure freedom (ILAE class 1), 6 had ILAE class 4 and 2 had ILAE class 5 outcomes, respectively. Mean reduction in daily seizure frequency was found to be 53.5 ± 60.3% (1-sided p-value for paired t-test = 0.04), with a 50% responder rate of 55.6%.ConclusionVNS may be considered as a therapeutic option in patients with medically refractory absence epilepsy.     

Effect of Long-Term Treatment with Vagus Nerve Stimulation on Mood and Quality of Life in Korean Patients with Drug-Resistant Epilepsy

Background and PurposeThis study aimed to determine the long-term effects of vagus nerve stimulation (VNS) treatment on suicidality, mood-related symptoms, and quality of life (QOL) in patients with drug-resistant epilepsy (DRE). We also investigated the relationships among these main effects, clinical characteristics, and VNS parameters.MethodsAmong 35 epilepsy patients who underwent VNS implantation consecutively in our epilepsy center, 25 patients were recruited to this study for assessing the effects of VNS on suicidality, mood-related symptoms, and QOL. The differences in these variables between before and after VNS treatment were analyzed statistically using paired t-tests. Multiple linear regression analyses were also performed to determine how the patients'' demographic and clinical characteristics influenced the variables that showed statistically significant changes after long-term VNS treatment.ResultsAfter VNS, our patients showed significant improvements not only in the mean seizure frequency but also in suicidality, depression, and QOL. The reduction in depression was associated with the improvement in QOL and more-severe depression at baseline. The reduction in suicidality was associated with higher suicidality at baseline, smaller changes in depression, and less-severe depression at baseline. Improved QOL was associated with lower suicidality at baseline.ConclusionsThis study found that VNS decreased the mean seizure frequency in patients with DRE, and also improved their depression, suicidality, and QOL. These results provide further evidence for therapeutic effect of VNS on psychological comorbidities of patients with DRE.