Vagus nerve stimulation for drug resistant epilepsy case series

SElner et al. from the Department of Neurosurgery, University of Illinois at Chicago, published the thirty-day outcomes of adults undergoing VNS from 2005-2016 collected from the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database. Readmission rates, reoperation rates, hospital length of stay, operative time, and complications were assessed. A comprehensive literature search was then performed to identify historically reported complication rates.

Seventy-seven patients met inclusion and exclusion criteria. A 30-day risk profile revealed low readmission (6.2%), reoperation (1.3%), and postoperative infection (1.3%) rates. Mean operative time was 81.7 minutes, and average length of stay was 0.27 days. Most (87.0%) patients were discharged on the day of operation.

This study provides a current “snapshot” of risks and outcomes in VNS, revealing a safe 30-day risk profile. Greater utilization may be of benefit in this fragile population 1).

Data from 130 consecutive patients implanted with a VNS device between the years 2000 and 2013 was analyzed. Seizure frequency and pharmacological antiepileptic drug (AED) treatments were recorded prior to as well as at one, two, and five years after VNS implantation.

Median age at epilepsy onset was five years and mean years from diagnosis to VNS implantation was 16.5 years. There was a significant seizure reduction overall (all p < 0.001). The responder (≥50% seizure frequency reduction) rate increased from 22.1 to 43.8% between the first and fifth year for the cohort as a whole, with the largest increase between the first and second year (22.1-38.1%) and regardless of AED changes. VNS effectiveness did not differ between patients who altered or remained on the same AEDs. Patients were treated with a median of three AEDs throughout the study and the number of AEDs significantly increased after two (p = 0.007) and five (p = 0.001) years.

VNS is a well-tolerated palliative neuromodulatory treatment for drug resistant epilepsy with a 43.8% seizure reduction after five years. This data supports the idea that VNS effectiveness increases with time. Therefore we suggest that VNS should be evaluated for at least two years after implantation. AED changes should try to be kept to a minimum during evaluation in order to determine the effectiveness of VNS 2).

74 adults from the Department of Neurosurgery, St. Anne's University Hospital, Masaryk University, Brno, Czech Republic. Electronic address: with VNS for 10 to 17 years were evaluated yearly as: non-responder - NR (seizure frequency reduction <50%), responder - R (reduction ≥ 50% and <90%), and 90% responder - 90R (reduction ≥ 90%). Delayed R or 90R (≥ 4 years after surgery), patients with antiepileptic medication changes and battery or complete system replacement were identified. Statistical analysis of potential outcome predictors (age, seizure duration, MRI, seizure type) was performed.

The rates of R and 90R related to the patients with outcome data available for the study years 1, 2, 10, and 17 were for R 38.4%, 51.4%, 63.6%, and 77.8%, and for 90R 1.4%, 5.6%, 15.1%, and 11.1%. The absolute numbers of R and 90R increased until years 2 and 6. Antiepileptic therapy was changed in 62 patients (87.9%). There were 11 delayed R and four delayed 90R, with medication changes in the majority. At least one battery replacement was performed in 51 patients (68.9%), 49 of whom R or 90R. VNS system was completely replaced in 7 patients (9.5%) and explanted in 7 NR (9.5%). No significant predictor of VNS outcome was found.

After an initial increase, the rate of R and 90R remains stable in long-term follow-up. The changes of antiepileptic treatment in most patients potentially influence the outcome. Battery replacements or malfunctioning system exchange reflect the patient's satisfaction and correlate with good outcomes 3).

A retrospective review was conducted in children with a history of at least two SE, who had VNS implantation and had at least one year follow up after the procedure.

Sixteen patients met inclusion/exclusion criteria. The median age of seizure onset and surgery was 1.3 years and 9.0 years, respectively. Prior to VNS implantation, 81% (13/16) of patients had ≥one seizure per month when all seizure types were combined. 75% (12/16) of patients experienced  ≥one generalized convulsive seizure per month. The median number of SE prior to VNS was three (2-9), and 63% (10/16) had at least one SE during a year prior to implantation. The proportion of patients who did not have any SE one year after VNS implantation increased compared to the year prior (75% vs. 37%, p = 0.07). The seizure frequency decreased in a minority of patients when all seizure types were combined (20% at one year, p = 1.00, 44% at the last follow up, p = 0.55), but generalized convulsive seizure decreased in 69% of patients at one year (p = 0.01) and 75% of patients at last follow up (p = 0.01).

VNS appears to have favorable impact on SE and generalized convulsive seizures in children with medically intractable epilepsy 4).

Arcand et al., retrospectively assessed the efficacy of VNS in 30 adult patients with epilepsy treated with >6 months of follow-up. The criteria for implantation were the following: (1) not a candidate for resective epilepsy surgery, (2) drug-resistant epilepsy, (3) impairment of quality of life, (4) no other option of treatment, and (5) patients with idiopathic generalized epilepsy who fail to be controlled with appropriate AEDs. Theu assessed sociodemographics, seizure etiology, seizure classification, and AEDs used during treatment with VNS. They assessed adverse effects and efficacy. Responder rate was defined as >50% seizure improvement from baseline.

Thirty patients (females, 18; males, 12; age, 35.1±13.3 years) were included. After 6, 12, 24, and 36 months of follow-up, the response rates were: 13/30 (43%), 13/27 (48%), 9/22 (41%), and 8/16 (50%), respectively; none was seizure free. Fifty-seven percent, 33%, 59%, and 81% of patients had changes of medication type or dose at 6, 12, 24, and 36 months respectively. In the majority of patients, the change of medication consisted of an increase in the dose of AEDs.

The study shows that VNS is an effective therapy, although significant changes in medications were done along with the therapy; therefore, the real effect of VNS could be controversial 5).

Between 2006 and 2013, 32 consecutive epileptic patients (14 male and 18 female) were enrolled at our Institute for VNS implantation. In all cases resective surgery had previously been excluded by the use of a noninvasive presurgical study protocol. Mean age was 32 years (range 18-50), and mean epilepsy duration 23 years (range 11-39). All subjects were followed-up for at least 2 years (mean 6 years, range 2-9) after VNS implantation. Patients were considered responders when a reduction of seizures of more than 50 % was reported.

All patients had complex partial seizures, in 81 % of the patients with secondary generalization and in 56 % with drop attacks. Neurological examination revealed focal deficits in 19 % of the patients. Brain magnetic resonance imaging (MRI) was positive in 47 % of the patients. No surgical complications were observed in this series. Three patients were lost to follow-up. Twelve patients were classified as responders. Among the others, 1 patient experienced side effects (snoring and groaning during sleep) and the device was removed.

The data confirm that VNS is a safe procedure and a valid palliative treatment option for drug-resistant epileptic patients not suitable for resective surgery 6).

A retrospective analysis of 158 pediatric patients with epilepsy resistant to pharmacological and non pharmacological treatment including surgery that were treated with vagus nerve stimulation between 2001-2015. Patients with progressive encephalopathies, and congenital heart disease were excluded.

158 patients (80 male) were included, with a mean age at implantation of 11.4 years and a mean age at evolution of epilepsy of 9.5 years. Time of follow-up: 1-15 years (median: 6.9 years). Patient's age at this time: 2-31 years (median: 14.1 years). Effectiveness: 66.5% of patients showed more or equal at 50% of seizure control at 24 months of implant. Just three patients showed severe side effects (1.8%). Minor side effects were seen in 26 patients (16.4%). Without side effects: 129 (81.8%).

Vagus nerve stimulation is an effective, tolerable and safe therapy in our pediatric series with refractory epilepsy 7).

Pakdaman et al., selected 48 patients with partial-onset drug-resistant epilepsy. Implantations were performed in the neurosurgery department of Loghman Hospital, Tehran, Iran. Follow-up visits were done on monthly bases for 5 years. Forty-four patients completed the study. Mean age of patients was 24.4 years. Mean years of epilepsy history was 14 years. The mean number of anti-epileptic drugs did not significantly change over five years (p = 0.15). There was no exacerbation of epilepsy; however, one patient discontinued his therapy due to unsatisfactory results. Five patient had more than 50 %, and 26 patients (59 %) had 25-49 % reduction in the frequency of monthly seizures persistently. Overall mean frequency of monthly seizures decreased by 57.8, 59.6, 65, 65.9, and 67 %, in 1st, 2nd, 3rd, 4th, and 5th years of follow-up, respectively. Most common side effects were as follows: hoarseness (25 %) and throat discomfort (10 %). We found VNS as a safe and effective therapy for drug-resistant epilepsy, with an approximate long-term decrease in mean seizure frequency of 57.8-67 %. Thus, VNS is recommended for suitable patients in developing countries 8).

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.

Overall, responder rate was 54% with 5.7% children becoming seizure-free. The only factor in the 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.

This 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 9).

Meng et al., retrospectively assessed the clinical outcome of 94 patients with PRE, who were treated with VNS at Beijing Fengtai Hospital and Beijing Tiantan Hospital between November 2008 and April 2014 from our database of 106 consecutive patients. The clinical data analysis was retrospectively examined.

Seizure frequency significantly decreased with VNS therapy after intermittent stimulation of the vagus nerve. At last follow-up, we found McHugh classifications of Class I in 33 patients (35.1%), Class II in 27 patients (28.7%), Class III in 20 patients (21.3%), Class IV in 3 patients (3.2%), and Class V in 11 patients (11.7%). Notably, 8 (8.5%) patients were seizure-free while ≥50% seizure frequency reduction occurred in as many as 60 patients (63.8%). Furthermore, with regard to the modified Engel classification, 12 patients (12.8%) were classified as Class I, 11 patients (11.7%) were classified as Class II, 37 patients (39.4%) were classified as Class III, 34 patients (36.2%) were classified as Class IV. We also found that the factors of gender or age are not associated with clinical outcome.

This comparative study confirmed that VNS is a safe, well-tolerated, and effective treatment for Chinese PRE patients. VNS reduced the seizure frequency regardless of age or gender of studied patients 10).

347 children (aged 6 months to 17.9 years at the time of implant). At 6, 12, and 24 months after implantation, 32.5%, 37.6%, and 43.8%, respectively, of patients had ≥ 50% reduction in baseline seizure frequency of the predominant seizure type. The responder rate was higher in a subgroup of patients who had no change in antiepileptic drugs (AEDs) during the study. Favorable results were also evident for all secondary outcome measures including changes in seizure duration, ictal severity, postictal severity, quality of life, clinical global impression of improvement, and safety. Post hoc analyses demonstrated a statistically significant correlation between VNS total charge delivered per day and an increase in response rate. VNS Therapy is indicated as adjunctive therapy in children with focal, structural epilepsies, who for any reason are not good candidates for surgical treatment following the trial of two or more AEDs. Children with predominantly generalized seizures from genetic, structural epilepsies, like Dravet syndrome or Lennox-Gastaut syndrome, could also benefit from VNS Therapy.

The results demonstrate that adjunctive VNS Therapy in children with drug-resistant epilepsy reduces seizure frequency and is well tolerated over a 2-year follow-up period. No new safety issues were identified. A post hoc analysis revealed a dose-response correlation for VNS in patients with epilepsy 11).

Elliot et al., retrospectively reviewed 141 consecutive cases involving children (75 girls and 66 boys) with treatment-resistant epilepsy in whom primary VNS implantation was performed by the senior author between November 1997 and April 2008 and who had at least 1 year of follow-up since implantation. The patients' mean age at vagus nerve stimulator insertion was 11.1 years (range 1-18 years). Eighty-six children (61.0%) were younger than 12 years at time of VNS insertion (which constitutes off-label usage of this device).

Follow-up was complete for 91.8% of patients and the mean duration of VNS therapy in these patients was 5.2 years (range 25 days-11.4 years). Seizure frequency significantly improved with VNS therapy (mean reduction 58.9%, p < 0.0001) without a significant reduction in antiepileptic medication burden (median number of antiepileptic drugs taken 3, unchanged). Reduction in seizure frequency of at least 50% occurred in 64.8% of patients and 41.4% of patients experienced at least a 75% reduction. Major (3) and minor (6) complications occurred in 9 patients (6.4%) and included 1 deep infection requiring device removal, 1 pneumothorax, 2 superficial infections treated with antibiotics, 1 seroma/hematoma treated with aspiration, persistent cough in 1 patient, severe but transient neck pain in 1 patient, and hoarseness in 2 patients. There was no difference in efficacy or complications between children 12 years of age and older (FDA-approved indication) and those younger than 12 years of age (off-label usage). Linear regression analyses did not identify any demographic and clinical variables that predicted response to VNS.

Vagus nerve stimulation is a safe and effective treatment for treatment-resistant epilepsy in young adults and children. Over 50% of patients experienced at least 50% reduction in seizure burden. Children younger than 12 years had a response similar to that of older children with no increase in complications. Given the efficacy of this device and the devastating effects of persistent epilepsy during critical developmental epochs, randomized trials are needed to potentially expand the indications for VNS to include younger children 12).

100 consecutive patients were identified by means of operating room records. Data collected described the patient's epilepsy, previous and subsequent therapies, adverse events, nonepileptic changes, and outcomes.

Average age was 10.4 years; years of epilepsy, 8.5; total number of antiepileptic therapies, 8.4; and median monthly seizure frequency, 120. Data on seizure frequency at follow-up were available for 96 of the 100 patients. Forty-five percent of patients achieved greater than 50% reduction; and 18% had had no seizures for the last 6 months. Response was similar in patients with more than 7 years of refractory epilepsy as compared with patients with a shorter history. Magnet-generated, on-demand current reduced seizure intensity in almost half of the patients with available data. Generator infections occurred in 3 patients. Twenty-four patients had their generators removed. Subsequently, 2 of these patients died.

Seizure reduction was the same in patients younger than 12 years and 12 years or older and in patients with shorter and longer histories of refractory epilepsy. Adverse effects were few in this population, particularly in those younger than 12 years. Vagal nerve stimulation appears to be a relatively safe and potentially effective treatment for children with severely intractable epilepsy 13).

Sixteen patients, ten of whom participated in a larger multicenter double-blind trial on the efficacy of VNS in epilepsy, and six who participated in pilot studies, consented to participate in the present study. Ten patients received HIGH stimulation and six patients LOW stimulation for the 3-month trial. Cerebrospinal fluid (CSF) samples (16 ml) were collected both before and after 3 months of VNS. Amino acid and neurotransmitter metabolites were analyzed. Four patients responded to VS with more than a 25% seizure reduction after 3 months. Mean and median concentrations of phosphoethanolamine (PEA) increased in responders and decreased in nonresponders. Free GABA increased in both groups but more so in the nonresponders. After 9 months of VS (6-9 months on HIGH stimulation) 4 of 15 patients had more than 40% seizure reduction. There were significant correlations between seizure reduction and increases in asparagine, phenylalanine, PEA, alanine and tryptophan concentrations. Comparison between patients with HIGH or LOW stimulation showed a significant increase in ethanolamine (EA) in the HIGH group and a decrease in glutamine in the LOW group. All patients regardless of response or stimulation intensity showed significantly increased total and free GABA levels. A decrease in CSF aspartate was marginally significant. Other trends were decreases in glutamate and increases in 5-hydroxyindoleacetic acid. Chronic VNS appears to have an effect on various amino acids pools in the brain 14).

Penry et al., demonstrated that vagus nerve stimulation in four patients resulted in complete seizure control in two, a 40% reduction of seizure frequency in one, and no change in seizure frequency in the other. Side effects (hoarseness, stimulation sensation in the neck, and hiccups) were transient and occurred concomitantly with stimulation. All patients tolerated increasing stimulation parameters well. The results, however, were inconclusive because of the brief duration (6-12 months) of follow-up 15).

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