Vagus Nerve Stimulator Placement Research Articles

924 Corpus Callosotomy for Intractable Epilepsy: A Contemporary Series of Operative Factors and Overall Complication Rate

INTRODUCTION: Corpus callosotomy is an effective treatment for atonic seizures in medically refractory epilepsy. Recently, laser interstitial thermal therapy has been adapted as a less invasive method to achieve similar results, yet technical challenges associated with this nascent approach persist. A modern series of corpus callosotomies performed by open craniotomy is lacking in the literature, a fact which highlights the importance of establishing contemporary complication rates for this operation to compare with newer methodologies. METHODS: We retrospectively reviewed institutional data for patients who underwent first time open callosotomy from 2005 to 2022. Demographic and clinical variables were collected and analyzed with a focus on operative factors and complication rates. RESULTS: 105 patients were included in the study with a mean age of 9.39 years (0.67-24.17 years). 58.1% of patients were male (61), and one surgeon performed a majority (76.20%, 80) of the operations with two other surgeons performing the remainder (21.9% and 1.90%, respectively). In total, 63 complete, 31 subtotal (anterior 70-99%), and 1 posterior (40%) callosotomies were performed. Blood loss was available for 102/105 patients with a mean of 96.67 mL (10-500 mL), and mean operative time was calculated as 226.76 minutes (45-504 minutes) from 76/105 patients by excluding those patients who underwent concurrent vagal nerve stimulator placement or revision. Operative complication rate was determined to be 6.67% and was comprised of 3 pseudomeningoceles, 3 superficial wound infections, and 1 delayed intraparenchymal hemorrhage. No venous infarcts were observed on postoperative MRI. CONCLUSIONS: This the largest single center series of open callosotomy patients describes important updated metrics to help evaluate new techniques being developed for the surgical treatment of atonic seizures in medically intractable epilepsy.

Twists in genetic mitochondria: Unraveling a case of mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes overlapping with myoclonic epilepsy with ragged red fibers

This case report presents a 23-year-old female with a complex medical history, initially diagnosed with juvenile myoclonic epilepsy, later discovered to have the m.3243A>G variant associated with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS). Despite a typical myoclonic epilepsy with ragged red fibers (MERRF) phenotype, genetic testing confirmed a singular MELAS mutation. The patient exhibited diverse symptoms, including seizures, chronic migraines, myoclonus, and visual disturbances. Diagnostic studies revealed basal ganglia calcifications and progressive brain MRI abnormalities consistent with mitochondrial dysfunction. Additionally, ophthalmologic exams identified features indicative of MELAS pigmentary retinopathy. The discussion highlights the clinical and genetic diversity of mitochondrial disorders, emphasizing the challenges in distinguishing overlapping phenotypes. The patient’s mitochondrial DNA heteroplasmy influenced the variable onset and severity of symptoms. The case underscores the importance of comprehensive genetic investigations, as the m.3243A>G variant is associated with both MELAS and MERRF, leading to diagnostic complexities. Management strategies, primarily symptom-focused due to the lack of a standardized treatment approach, include prophylactic arginine, taurine, and coenzyme Q10 supplementation. The patient’s response to various medications, including vagal nerve stimulator placement, Botox injections, and novel treatments like ASP0367, demonstrates the ongoing efforts to address symptoms and improve quality of life. This report contributes to the understanding of mitochondrial overlap syndromes, offering insights into the diagnostic challenges and management complexities associated with MELAS and MERRF. The case underscores the need for a multidisciplinary approach, combining clinical, genetic, and therapeutic considerations, to optimize care for individuals with mitochondrial encephalopathies.

Intraoperative nerve stimulation during vagal nerve stimulator placement.

Vagal nerve stimulation (VNS) is a palliative treatment for refractory epilepsy and intraoperative nerve stimulation is applied to the vagal and other nerves to prevent electrode misplacement. We evaluated these thresholds to establish intraoperative monitoring procedures for VNS surgery. Forty-six patients who underwent intraoperative nerve stimulation during VNS placement were enrolled. The vagal nerve and other exposed nerves were electrically stimulated during surgery, and muscle contraction was confirmed by electromyography of the vocal cords and visual recognition of cervical muscle contraction. The nerve thresholds and the most sensitive parts of the vagal nerve were analyzed retrospectively. The stimulation of vagal nerves induced vocal cord responses in all 46 patients; the median thresholds of the most sensitive parts and all parts were 0.2 mA (range: 0.05-0.75 mA) and 0.25 mA (range: 0.15-1.5 mA), respectively. The medial middle region was identified as the most sensitive part of the vagal nerve in the majority of participants (82.5%). In 11 patients, other cervical nerves were stimulated and sternohyoid muscle contraction was induced with a median threshold of 0.35 mA (range: 0.1-0.7 mA) in eight patients, while sternocleidomastoid muscle contraction was induced with a median threshold of 0.2 mA (range: 0.1-0.2 mA) in three. Intraoperative stimulation of vagal nerves induces vocal cord responses with locational variations, and the middle part stimulation could minimize the stimulus intensities. The nerves innervating the sternohyoid and sternocleidomastoid muscles may be exposed during the procedure. Knowledge of these characteristics will enhance the effectiveness of this technique in future applications.

Intractable hiccups after VNS implantation: a case report

BackgroundHiccups (medically termed, “singultus”), when intractable, can cause significant medical consequences such as aspiration, malnutrition, and depression, leading to poor quality of life. Several case reports have shown that vagus nerve stimulator (VNS) implantation can help treat central idiopathic intractable hiccups. However, we present a contrary case of a patient who developed intractable singultus following VNS placement for medically refractory epilepsy.Case presentationWe report a 71-year-old male patient with drug-resistant epilepsy who underwent VNS implantation and developed intractable hiccups shortly thereafter. The hiccups were severe and persistent, such that the patient developed a Mallory-Weiss tear, which required intensive care, invasive intubation and mechanical ventilation, and a prolonged rehabilitation course. Despite multiple therapies including phrenic nerve block and Nissen fundoplication, the patient’s hiccups persisted and only stopped once the VNS was permanently deactivated.ConclusionsLittle is known about the incidence of hiccups after VNS implantation. We present one case of hiccups as a direct consequence of VNS implantation. The clinical impact of this report is significant given the relative unfamiliarity of hiccups as an adverse effect of VNS implantation. Neurologists and epileptologists, who present VNS implantation as a surgical option for seizure control to their patients, should be aware of the possibility of singultus development and its significant physical and emotional ramifications.

1004 A novel use of adaptive servo ventilation for VNS-induced central sleep apnea in an adolescent with refractory epilepsy

Abstract Introduction Epilepsy is frequently encountered in the pediatric population and some patients are treated by stimulation of the vagus nerve to reduce their seizure frequency. Vagus nerve stimulation (VNS) may induce central sleep apnea. Adaptive servo ventilation is a known treatment option for central sleep apnea in certain adult patients with heart failure and Cheyne-Stokes respiration but is infrequently utilized in the pediatric population. Report of case(s) A 17-year-old male with a history of intractable generalized epilepsy, VNS placement, obstructive sleep apnea (OSA) and central sleep apnea (CSA) presented to our tertiary care center for management of his sleep disordered breathing. Initial management of sleep disordered breathing included CPAP for OSA. After VNS placement, the patient began to have a high residual apnea-hypopnea index on data card download of his CPAP. Polysomnography (PSG) was performed on CPAP and CSA events were noted that correlated with VNS firing. BiPAP was titrated and was unsuccessful in treating the CSA. VNS adjustment did not impact the sleep disordered breathing. Repeat titration with adaptive servo ventilation successfully treated the OSA and CSA. In follow up, the patient is tolerating ASV with improvement in his nocturnal sleep disordered breathing events and his daytime functioning. Conclusion Central sleep apnea can be induced by vagus nerve stimulation. This unique case documents successful treatment of vagus nerve stimulation induced central sleep apnea by adaptive servo ventilation in an adolescent patient. Support (if any)

0988 Vagal Nerve Stimulation and OSA

Abstract Introduction We present a case of obstructive sleep apnea (OSA) worsened by implantation of a vagal nerve stimulator (VNS). A 22-year-old M with PMH of autism and refractory epilepsy s/p VNS implantation was diagnosed with moderate OSA. His parents noted that his sleep-disordered breathing worsened after VNS implantation. He was started on APAP 4-12 cm H2O. Review of adherence data revealed an elevated residual apnea-hypopnea index (AHI) despite nightly usage. PAP titration study was obtained with improvement of AHI on 16 cm H2O. Despite consequent use of determined pressure settings, residual AHI remained elevated. In consultation with the patient’s neurologist, VNS settings were gradually down titrated. Residual AHI improved and remained low as CPAP settings were subsequently weaned. Report of case(s) The vagus nerve is part of the parasympathetic nervous system. Afferent fibers project to cortical regions involved in seizure activity. Vagal nerve activation leads to desynchrony, thereby decreasing seizure activity.3 VNS, an adjunctive non-pharmacologic treatment of refractory epilepsy, consists of a generator with multiple adjustable settings and a lead connected to the left vagus nerve.1 VNS activation, in conjuction with medical therapy, can lead to decreased seizures. However, VNS may cause complications such as vocal cord dysfunction, laryngeal spasm, and dyspnea.2 In this case, VNS was noted to cause OSA due to increased airway obstruction, though the pathophysiological mechanism behind this has not been clearly delineated. 3 Conclusion Based on current evidence of precipitation or worsening OSA with VNS activation, screening and diagnostic testing for OSA in patients under evaluation for VNS placement should be considered. A multidisciplinary approach between Sleep Medicine and Neurology in conjunction with patient goals can lead to a balanced optimization of both epilepsy and OSA management via adjustments of VNS settings, anti-epileptics, and CPAP. Support (if any) 1. VNS therapy epilepsy. Epilepsy Foundation. https://www.epilepsy.com/sites/default/files/atoms/files/516VNS_VNS_FINAL.pdf. December 20, 2022. 2. Ebben MR, Sethi NK, Conte M, Pollak CP, Labar D. Vagus nerve stimulation, sleep apnea, and CPAP titration. J ClinSleepMed. 2008 Oct 15;4(5):471-3. PMID: 18853706. 3. Parhizgar F, Nugent K, Raj R. Obstructive sleep apnea and respiratory complications associated with vagus nerve stimulators. J ClinSleepMed. 2011 Aug 15;7(4):401-7. doi: 10.5664/JCSM.1204. PMID: 21897779.

Postoperative seizure freedom after vagus nerve stimulator placement in children 6 years of age and younger.

Food and Drug Administration (FDA) approval for vagus nerve stimulator (VNS) implantation is limited to patients older than 4 years of age with medically refractory partial-onset seizures. In younger children with severe generalized epilepsy, however, VNS implantation remains off-label. In this study, the authors followed up on their previously reported cohort to review the longer-term safety and efficacy of VNS placement in children younger than 6 years with generalized medically refractory epilepsy (MRE), providing the largest cohort with > 2 years of follow-up to date in this age group. This was a retrospective observational cohort study of patients younger than 6 years of age with generalized MRE who underwent VNS implantation at a single institution between 2010 and 2020. Inclusion criteria encompassed failure of more than two antiepileptic drugs alone or in combination, neurologist referral for vagus nerve stimulation, informed consent with knowledge of the off-label status in young children, and > 1 year of follow-up. Outcome measures included seizure reduction rate ≥ 50% and postoperative morbidity defined nominally. Statistical analysis was conducted with Stata/SE. Forty-five patients were included: 11 patients younger than 4 years of age and 34 between 4 and 6 years of age. There were no intraoperative complications. Perioperative complications within 1 year occurred in 11% (n = 5) of the patients and included two wound infections, a mild cough, hyperactivity, hoarseness, and 1 patient with persistent surgical site pain. A seizure reduction ≥ 50% was observed in 36.4% (n = 4) of the patients younger than 4 years of age at the 6-month and 1-, 2-, and 5-year follow-ups. In the 4- to 6-year-old cohort, this was observed in 32.4% (n = 11) of the patients at 6 months, 41.2% (n = 14) at 1 year, 38.2% (n = 13) at 2 years, and 41.2% (n = 14) at 5 years. VNS implantation for patients younger than 4 years of age with generalized onset MRE has not been approved by the FDA. This retrospective study establishes feasibility, illustrates an acceptable safety profile in children younger than 6 years, and demonstrates efficacy comparable to that reported in older patients.

An economic evaluation of vagus nerve stimulation as an adjunctive treatment to anti-seizure medications for the treatment of drug resistant epilepsy in the United States

IntroductionPeople with recurrent epileptic seizures are typically treated with anti-seizure medications (ASMs). Around a third of epilepsy patients fail to achieve an adequate response to ASMs and may be eligible to receive vagus nerve stimulation (VNS) therapy for their drug-resistant epilepsy (DRE) if they are unsuited to surgery. VNS received approval from the United States (US) Food and Drug Administration agency. However, there has to date been no comprehensive cost effectiveness evaluation of VNS within the US setting. This study was designed, using a US Medicare perspective, to estimate costs and quality-adjusted life years (QALYs) associated with VNS as an adjunct to ongoing ASM therapy, compared to ASMs alone.MethodsWe developed a cohort state transition model in Microsoft Excel, with four health states defined by different percentage reductions in seizure frequency, with a 3-month cycle and transition probabilities derived from published clinical trials and registry data. Sensitivity analyses were conducted to understand the impact of parameter uncertainty. Costs included the VNS device, placement, programming, battery changes, and removal; ASM therapy; adverse events associated with VNS (dyspnea, hoarseness, and cough); and costs associated with seizure burden (i.e. hospitalizations, emergency department visits, neurologist visits).ResultsUnder base case assumptions, treatment with VNS was associated with a 0.385 QALY gain and a $109,678 saving per patient, when compared with ASM therapy alone. The incremental net monetary benefit (iNMB) was $128,903 at a threshold of $50,000 per QALY, with the positive iNMB indicating that VNS is a highly cost effective treatment. This result is explained by the modeled reduction in relative seizure frequency and associated reduction in healthcare resource use that the VNS group experienced. Sensitivity analyses supported this conclusion.ConclusionsVNS was evaluated as a cost effective addition to the current standard of care in the treatment of DRE in the US Medicare context.

Vagus nerve stimulator revision in pediatric epilepsy patients: a technical note and case series.

Vagus nerve stimulation (VNS) is an adjunctive treatment in children with intractable epilepsy. When lead replacement becomes necessary, the old leads are often truncated and retained and new leads are implanted at a newly exposed segment of the nerve. Direct lead removal and replacement are infrequently described, with outcomes poorly characterized. We aimed to describe our experience with feasibility of VNS lead removal and replacement in pediatric patients. Retrospective review examined 14 patients, at a single, tertiary-care, children's hospital, who underwent surgery to replace VNS leads, with complete removal of the existing lead from the vagus nerve and placement of a new lead on the same segment of the vagus nerve, via blunt and sharp dissection without use of electrocautery. Preoperative characteristics, stimulation parameters, and outcomes were collected. Mean age at initial VNS placement was 7.6years (SD 3.5, range 4.5-13.4). Most common etiologies of epilepsy were genetic (5, 36%) and cryptogenic (4, 29%). Lead replacement was performed at a mean of 6.0years (SD 3.8, range 2.1-11.7) following initial VNS placement. Reasons for revision included VNS lead breakage or malfunction. There were no perioperative complications, including surgical site infection, voice changes, dysphagia, or new deficits postoperatively. Stimulation parameters after replacement surgery at last follow-up were similar compared to preoperatively, with final stimulation parameters ranging from 0.25mA higher to 1.5mA lower to maintain baseline seizure control. The mean length of follow-up was 7.9years (SD 3.5, range 3.1-13.7). Removal and replacement of VNS leads are feasible and can be safely performed in children. Further characterization of surgical technique, associated risk, impact on stimulation parameters, and long-term outcomes are needed to inform best practices in VNS revision.

Endotracheal Tube Electrode Neuromonitoring for Placement of Vagal Nerve Stimulation for Epilepsy: Intraoperative Stimulation Thresholds

ABSTRACT Vagal nerve stimulators (VNS) are indicated as a palliative treatment for medically refractory epilepsy. The vagus nerve may have a variable position within the carotid sheath and may be confused with a prominent ansa cervicalis. The objective of this study was to describe an intraoperative neuromonitoring technique for VNS placement and provide stimulation thresholds that may aid in the creation of stimulation protocols. A retrospective study was performed assessing 40 patients undergoing intraoperative vocal cord monitoring during vagal nerve stimulator placement surgery. Endotracheal electrodes were utilized to record vocal cord activity at various surgical time points. The stimulation thresholds were tested at the time of opening of the carotid sheath (mean 0.35 mA [range 0.08–1.00]), after full and circumferential dissection of the vagus nerve (0.34 mA [0.10–0.90]), after tenting of the vagus nerve in preparation for placement of the electrode (0.22 mA [0.06–1.20]), and after electrode placement (0.26 mA [0.05–1.20]). The vagus nerve was identified in all patients; it was located behind the common carotid artery (CCA) in two patients, on top of the internal jugular vein (IJV) in one patient, and in the typical location between the CCA and IJV in the remainder of patients. The average size of the vagus nerve was 2.9 mm [1.5–5.0]. Intraoperative vagus nerve stimulation represents a safe adjunctive tool that can help localize the nerve, particularly in the setting of varying anatomy or hazardous dissections. It may help reduce the potential for vagal trunk damage or electrode misplacement and potentially improve clinical outcomes.

Outcomes following surgical management of vagus nerve stimulator-related infection: a retrospective multi-institutional study.

Surgical site infection (SSI) is a rare but significant complication after vagus nerve stimulator (VNS) placement. Treatment options range from antibiotic therapy alone to hardware removal. The optimal therapeutic strategy remains open to debate. Therefore, the authors conducted this retrospective multicenter analysis to provide insight into the optimal management of VNS-related SSI (VNS-SSI). Under institutional review board approval and utilizing an institutional database with 641 patients who had undergone 808 VNS-related placement surgeries and 31 patients who had undergone VNS-related hardware removal surgeries, the authors retrospectively analyzed VNS-SSI. Sixteen cases of VNS-SSI were identified; 12 of them had undergone the original VNS placement procedure at the authors' institutions. Thus, the incidence of VNS-SSI was calculated as 1.5%. The mean (± standard deviation) time from the most recent VNS-related surgeries to infection was 42 (± 27) days. Methicillin-sensitive staphylococcus was the usual causative bacteria (58%). Initial treatments included antibiotics with or without nonsurgical procedures (n = 6), nonremoval open surgeries for irrigation (n = 3), generator removal (n = 3), and total or near-total removal of hardware (n = 4). Although 2 patients were successfully treated with antibiotics alone or combined with generator removal, removal of both the generator and leads was eventually required in 14 patients. Mild swallowing difficulties and hoarseness occurred in 2 patients with eventual resolution. Removal of the VNS including electrode leads combined with antibiotic administration is the definitive treatment but has a risk of causing dysphagia. If the surgeon finds dense scarring around the vagus nerve, the prudent approach is to snip the electrode close to the nerve as opposed to attempting to unwind the lead completely.

Hyperglycemia With Use of Vagal Nerve Stimulator

Abstract Introduction: In patient with diabetes and refractory epilepsy requiring vagal nerve stimulator (VNS), glycemic management can be challenging. Clinical experience is limited in this scenario. Case Report: A 67-year-old male, BMI 30 kg/m2, with history of type 2 diabetes and hemispheric hemangioma complicated by seizure disorder is referred to our diabetes clinic for evaluation of persistent hyperglycemia. The patient reports 25-year history of seizures that have been difficult to control with antiepileptic drugs alone and eventually requiring VNS placement. Patient has normal kidney (eGFR > 60mL/min) and liver function. His antiepileptic drug regimen consisted of gabapentin and as needed lorazepam. He was never on glucocorticoids. Glycated hemoglobin (HgA1c) at our initial evaluation was 10.1%. His anti-glycemic regimen consisted of glipizide monotherapy. Fasting and pre-prandial blood glucose were in the 200-400mg/dL range with occasional values higher than 500mg/dL. This was confirmed with 14-day continuous glucose monitoring that showed average blood glucose of 287mg/dL with 100 percent above target (higher than 180 mg/dL). We optimized therapy by adding once daily glargine, pioglitazone and continued glipizide. At follow up visit, HgA1c still remained high at 10.5%, despite medication adherence. Patient emphasized that hyperglycemia was related to VNS use and given documented hyperglycemia with blood glucose range 500–600 mg/dL when on higher output current of 2 milliamps, his neurologist approved a trial off VNS for 4 weeks. His glucose improved to average less than 200 mg/dL and HgA1c decreased to 9.1% on the same anti-glycemic regimen. Device was re-started due to recurrence of seizures, however the output current and “on time” were reduced to minimal effective range for optimizing seizure therapy while avoiding hyperglycemia. Subsequent HgA1C improved to 8.7%. Discussion: VNS is a FDA approved device for epilepsy and depression. It works by intermittent stimulation or “on/off” periods. In animal studies, elevation of blood glucose was noted with afferent stimulation. Conversely, efferent activation lowers blood glucose. There are limited human studies on the effects of vagal nerve stimulation on glycemic control. The few available, showed variation in blood glucose based on output current and length of on/off period. This should be factored in during glycemic evaluation and management and close collaboration with neurology is essential. Reference: (1) Strauss H, et al. Cervical Vagal Nerve Stimulation Impairs Glucose Tolerance and Suppresses Insulin Release in Conscious Rats. Physiological Reports 2018; 6(24): 1–9 (2) Strauss H, et al. Effect of Vagus Nerve Stimulation on Blood Glucose Concentration in Epilepsy Patients - Importance of Stimulation Parameters. Physiological Reports 2019; 7(14): 1–10

Epilepsy surgery in stroke-related epilepsy

PurposeTo provide a descriptive analysis on the presurgical evaluation and surgical management of a cohort of patients with stroke related epilepsy (SRE). MethodsWe retrospectively examined the clinical characteristics, results of non-invasive and invasive presurgical evaluation, surgical management and outcome of consecutive patients with drug-resistant SRE in our institution from January 1, 2013 to January 1, 2020. ResultsTwenty-one of 420 patients (5%) who underwent intracranial EEG (iEEG), resective epilepsy surgery and/or vagus nerve stimulation (VNS) placement, had SRE. Of 13 patients who had iEEG, the ictal onset (IO) was exclusively within the stroke lesion in only one patient. In five patients the IO was extra-lesional and in the remaining seven patients it included the stroke lesion as well as extra-lesional structures. The IO included the mesial temporal region in 11 of the 13 patients (85%). The posterior margin of the stroke lesion was always involved. Five patients underwent surgery without iEEG. In total, 10 patients underwent resective surgery, four VNS placement and two had both corpus callosotomy and VNS placement. Of the patients who had resective surgery, nine were Engel I or II at last follow up. ConclusionWe found that seizures in patients with drug resistant SRE were more frequently originated in the mesial temporal region than in the stroke lesion itself. Despite the complex epileptic network underlying drug-resistant SRE, a thorough presurgical assessment and adequate use of surgical options can lead to excellent surgical outcomes.

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

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. 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. 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. 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.

Stimulation of the Anterior Nucleus of the Thalamus for Epilepsy: A Canadian Experience.

To describe the experience with Anterior Nucleus of the Thalamus-Deep Brain Stimulation (ANT-DBS) for the treatment of epilepsy at a Canadian Center. All patients who underwent ANT-DBS implantation between 2013 (first patient implanted at our center) and 2020 were included. These patients had therapy-resistant epilepsy (TRE), were not candidates for resective surgery, and failed vagus nerve stimulation (VNS) treatment. Baseline of monthly seizure frequency was calculated within 3 months prior to VNS placement. Monthly seizure frequency was assessed at different points along the timeline: 3 months before ANT-DBS implantation as well as 3, 6, 12, 24, 36, 48, 60, and 72 months after ANT-DBS device placement. At each time point, seizure frequency was compared to baseline. Six patients were implanted with ANT-DBS. Three (50%) patients had multifocal epilepsy, one (16.6%) had focal epilepsy, and two (33.4%) had combined generalized and focal epilepsy. Two patients with multifocal epilepsy experienced a seizure reduction >50% in the long-term follow-up. Three (50%) patients did not showed improvement: two with combined generalized and focal epilepsy and one with focal epilepsy. There were not surgical or device-related side effects. Two (33.3%) patients presented mild and transient headaches as a stimulation-related side effect. ANT-DBS is an effective and safe treatment for focal TRE. Our experience suggests that patients with multifocal epilepsy due to regional lesion may benefit from ANT-DBS the most. Further investigations are required to determine optimal parameters of stimulation.

Vagal Nerve Stimulator Placement by a Vascular Surgeon.

Refractory seizure activity represents a difficult problem for both patients and practitioners. Implantation of the vagal nerve stimulator has been posited as an effective treatment for refractory seizure activity. These devices are inserted by placing leads into the carotid sheath along the vagus nerve. We evaluated a vascular surgeon's experience placing vagal nerve stimulators. We examined all patients treated with placement of vagal nerve stimulator by a single surgeon from October 2016 to October 2018. Data collected included demographics, medical and surgical history, intraoperative variables, and complications. Thirty-four patients underwent placement of a vagal nerve stimulator. About 29.4% had a previous vagal nerve stimulator placed on the ipsilateral side. Intraoperative bradycardia was seen in 1 patient. Postoperative complications were identified in 5 patients, all of which were transient dysphagia or changes in voice quality which did not require intervention. There was no significant difference between patients with the previous operation and those without for developing postoperative complications (P = .138). Average blood loss was higher in patients who had undergone previous stimulator placement than those who had not (P = .0223), and the operative time was longer (P ≤ .0001). Given the anatomical location of placement, vascular surgeons may be called upon to place these devices. In our single surgeon series, we found that the placement was safe, with minimal complications. Intraoperatively, this case appears to be more difficult (with higher blood loss and longer operative time) in patients who have had previous device placement, but this does not appear to lead to increased complications.

High lead impedances requiring revision during vagal nerve stimulator generator replacement.

Vagal nerve stimulation (VNS) therapy is among the growing options in the treatment of intractable epilepsy. The phenomenon of surprise lead impedance issues found at the time of surgery resulting in unplanned lead revision is a challenge with this type of device. We reviewed our experience with VNS revisions. We retrospectively reviewed the records of all adult and pediatric patients between January 2009 and September 2018 who underwent surgery for VNS therapy, including revision surgery. Office and operative notes were reviewed to obtain the indications and operative details for VNS placement. A total of 570 operations were reviewed. The indication was intractable epilepsy in all cases. Primary implantation was performed in 232 patients, while the remaining 338 cases were revision cases of various natures. Surprise high lead impedance was found in 10 (3%) of these cases, resulting in a significantly increased complexity of surgery in those instances. Lead impedance issues can be caused by disconnection, electrode fracture, hardware failure, or tissue scarring but ultimately require a more extended surgery than may be initially planned. Anticipating the potential for a more extensive operation than a simple generator replacement may prevent perioperative frustrations on both sides.

Vagus Nerve Stimulation versus Responsive Neurostimulator System in Patients with Temporal Lobe Epilepsy

Introduction: Patients with medically refractory temporal lobe epilepsy (TLE) are candidates for neuromodulation procedures. While vagus nerve stimulation (VNS) was historically the procedure of choice for this condition, the responsive neurostimulation system (RNS) has come into favor for its more targeted approach. While both VNS and RNS have been reported as efficacious treatments for TLE, the outcomes of these 2 procedures have not been directly compared. This study aims to compare outcomes following VNS versus RNS for TLE. Methods: We retrospectively reviewed the records of all patients with TLE who underwent VNS or RNS placement at our institution from 2003 to 2018. The primary outcome was change in seizure frequency. Other outcomes included Engel score, change in anti-epileptic medications, and complications. Results: Twenty-three patients met inclusion criteria; 11 underwent VNS and 12 underwent RNS. At baseline, the 2 groups were statistically similar regarding age at surgery, epilepsy duration, and preoperative seizure frequency. At last follow-up, both groups displayed reduced seizure frequency (mean reduction of 46.3% for the VNS group and 58.1% for the RNS group, p = 0.49). Responder rate, Engel score, and change in medications were statistically similar between groups. Compared to 0.0% of the VNS group, 13.3% of the RNS group experienced infection requiring re-operation. Conclusion: Despite their different mechanisms, VNS and RNS resulted in similar response rates for patients with TLE. We suggest that VNS should not be excluded as a treatment for patients with medically refractory TLE who are not candidates for resective or ablative procedures.

A Comparison of Vagal Nerve Stimulation and Responsive Neurostimulation for the Treatment of Medically Refractory Complex Partial Epilepsy

Background: Neuromodulatory applications such as vagus nerve stimulation (VNS) and responsive neurostimulation (RNS) are safe and effective strategies for medically intractable epilepsy secondary to complex partial seizures, but researchers have yet to compare their efficacies. Objective: The goal of this study is to compare VNS and RNS efficacy at reducing seizure frequency and complication rates in subjects with medically intractable epilepsy secondary to complex partial seizures. Methods: This is a retrospective chart review of 30 patients with medically intractable complex partial epilepsy, who underwent either VNS or RNS placement at a single institution between June 2012 and January 2016. There was a mean follow-up of 19 months. Seizure frequency reduction and complications were identified. Results: The median seizure frequency reduction was similar for VNS (66%) and RNS (58%). There was no major morbidity or mortality, and the frequency of minor complications was similar between VNS (15%) and RNS (18%). Conclusion: We found that VNS and RNS reduced the median seizure frequency similarly with no difference in morbidity or mortality. Further prospective studies are warranted as VNS and RNS therapy improves over time.

BS17. The “Uncommonly Common” horner syndrome following a VNS insertion

The Vagus nerve stimulation (VNS) therapy is approved in the USA as an adjunctive treatment in reducing the frequency of seizures in patients aged 4 years and older with partial-onset seizures refractory to antiepileptic drugs (AEDs). Globally, it has been implanted in more than 100,000 patients. Some of the commonly reported surgical complications of the device include infection, postoperative hoarseness, and pain. Here, we report a case of Horner syndrome subsequent to a VNS placement. Case report and literature review. A 61 year-old woman with drug-resistant focal epilepsy who previously underwent a selective left amygdalohippocampectomy at an outside hospital and achieved class 4 ILAE Epilepsy surgery outcome scale, underwent a VNS placement. There were no reported intraoperative complications. When seen in a follow-up 2 weeks post-operatively, the patient reported new onset excessive lacrimation and blurry vision in the left eye. A detailed examination revealed a left miotic pupil and partial left ptosis. She denied hemifacial anhidrosis and no changes in skin temperature or appearance were detected on the exam. Based on the above findings a diagnosis of left Horner syndrome was established. These signs and symptoms remained without improvement upon a subsequent follow-up, about 4 weeks post-operatively. When her findings first became apparent to the treating neurologist, the surgeon who placed the device was immediately contacted. The surgeon, however, did not find the discovery alarming, stating that Horner syndrome is “commonly observed” post-VNS implantation. An extensive literature search of VNS-related Horner syndrome returned maximum 7 references (both human and animal data) on PubMed and several book references on the Google search engine. Additionally, a limited poll of the epileptology colleagues and LivaNova representatives yielded zero personal reports of the phenomenon. Only two human studies with sizable patient samples that referenced the syndrome were identified. The first study retrospectively reviewed the charts of all adult epilepsy patients treated by VNS with ⩾1 year follow-up. Out of 34 patients (14 males; mean age = 29.9 years) who received a VNS, 1 patient developed Horner syndrome (2.9% of the patient group). The second study analyzed 251 procedures that were performed on 143 patients (81 males, 98 adults (mean age 35.8 years) and 45 children (mean age 10.1 years)). They found 1 case (0.7% of the group) of the syndrome. Based on the reviewed studies, Horner syndrome complicating a VNS implant was seen in 0.7–2.9% procedures. The pathophysiology of Horner syndrome following VNS placement has been postulated to reflect traction on the sympathetic fibers along the internal carotid artery or injury to or manipulation of the sympathetic plexus immediately beneath the carotid sheath. Horner syndrome is a potentially avoidable neurological complication following VNS placement, and while rare, is in fact an “uncommon” complication.