Vagus nerve stimulation induces changes in respiratory sinus arrhythmia of epileptic children during sleep

Vagus nerve stimulation and heart rate variability: A scoping review of a somatic oscillatory signal

The goal of this review is to synthesize the literature on vagus nerve stimulator (VNS)-related changes in heart rate variability (HRV) in patients with drug-resistant epilepsy (DRE) and assess the role of these changes in seizure relief. A scoping literature review was performed with the following inclusion criteria: primary articles written in English, involved implantable VNS in humans, and had HRV as a primary outcome. Twenty-nine studies were retrieved, however with considerable heterogeneity in study methods. The overall depression in HRV seen in DRE patients compared to healthy controls persisted even after VNS implant, indicating that achieving "healthy" HRV is not necessary for VNS therapeutic success. Within DRE patients, changes in frequency domain parameters six months after VNS implant returned to baseline after a year. The mechanism of how VNS reduces seizure burden does not appear to be significantly related to alterations in baseline HRV. However, the subtlety of sympathetic/parasympathetic signaling likely requires a more structured approach to experimental and analytic techniques than currently found in the literature.

Respiratory-cardiovascular interactions

Much of biology is rhythmical and comprises oscillators that can couple. These have optimized energy efficiency and have been preserved during evolution. The respiratory and cardiovascular systems contain numerous oscillators, and importantly, they couple. This coupling is dynamic but essential for an efficient transmission of neural information critical for the precise linking of breathing and oxygen delivery while permitting adaptive responses to changes in state. The respiratory pattern generator and the neural network responsible for sympathetic and cardiovagal (parasympathetic) tone generation interact at many levels ensuring that cardiac output and regional blood flow match oxygen delivery to the lungs and tissues efficiently. The most classic manifestations of these interactions are respiratory sinus arrhythmia and the respiratory modulation of sympathetic nerve activity. These interactions derive from shared somatic and cardiopulmonary afferent inputs, reciprocal interactions between brainstem networks and inputs from supra-pontine regions. Disrupted respiratory-cardiovascular coupling can result in disease, where it may further the pathophysiological sequelae and be a harbinger of poor outcomes. This has been well documented by diminished respiratory sinus arrhythmia and altered respiratory sympathetic coupling in animal models and/or patients with myocardial infarction, heart failure, diabetes mellitus, and neurological disorders as stroke, brain trauma, Parkinson disease, or epilepsy. Future research needs to assess the therapeutic potential for ameliorating respiratory-cardiovascular coupling in disease.

Sleep disordered breathing in children receiving vagus nerve stimulation therapy

OBJECTIVE

The 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.

METHODS

A 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.

RESULTS

22 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.

CONCLUSIONS

SDB 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.

Vagus nerve stimulation for pediatric patients with intractable epilepsy between 3 and 6 years of age: study protocol for a double-blind, randomized control trial

BACKGROUND

Recent clinical observations have reported the potential benefit of vagus nerve stimulation (VNS) as an adjunctive therapy for pediatric epilepsy. Preliminary evidence suggests that VNS treatment is effective for seizure reduction and mental development in young participants between 3 and 6 years of age who suffer from intractable epilepsy. However, robust clinical evidence for quantifying the difference of the efficacy and safety of VNS treatment in this specific patient population has yet to be reported.

METHODS/DESIGN

A two-armed, multicenter, randomized, double-blind, prospective trial will be carried out to evaluate whether VNS is beneficial and safe for pediatric epilepsy. Pediatric participants aged between 3 to 6 years old with intractable epilepsy will be recruited and randomly assigned to experimental and control groups with a 1:1 allocation using a computer-generating randomization schedule. Before enrollment, informed consent will be signed by the parents of the participants and the study researchers. Participants in the experimental group will receive electrical stimulation over 24 weeks under standard stimulation parameters. Participants in the control group will not receive any stimulation during the 12 weeks of the double-blind period. The guardians of the participants are required to keep a detailed diary to record seizure activity. Outcome assessments including seizure frequency, Gesell Mental Developmental Scale scores, use of antiepileptic drugs and dosages, and adverse events will be collected at baseline, 6, 12, 18 and/or 24 weeks after electrical stimulation is initiated. The effects of treatment will be analyzed with time and treatment group comparisons.

DISCUSSION

This trial will evaluate quantitative differences in efficacy and safety with/without VNS treatment for pediatric participants aged between 3 to 6 years with intractable epilepsy and will explore whether the current age range of VNS therapy can be expanded.

TRIAL REGISTRATION

ClinicalTrials.gov, ID: NCT03062514 , Registered on 23 February 2017.

Effects of vagus nerve stimulation on heart rate variability in children with epilepsy

PURPOSE

The aim of this study was to evaluate the effects of vagus nerve stimulation (VNS) on heart rate variability (HRV) in children with epilepsy.

METHODS

The subgroups of HRV, namely time domain (Standard deviation of NN interval (SDNN), SDNN index, Standard deviation of the averages of NN intervals (SDANN), Root mean square of successive differences (RMMSD), Adjacent NN intervals differing by more than 50 ms in the entire recording divided by the total number of all NN intervals (PNN50), triangular index) and frequency domain (Low-frequency (LF), High-frequency (HF), LF/HF), were investigated in 20 pediatric patients before and after 6 and 12months of VNS treatment during day and night by comparing their data with those of 20 control subjects. In addition, subgroups of age, epilepsy duration and localization, and antiepileptic drugs (AEDs) were also evaluated if they had further effects on basal HRV levels.

RESULTS

Increased heart rates (HRs); decreased SDNN, SDANN, RMMSD, and PNN50; and increased LF/HF ratios were identified before VNS therapy (p<0.05). Even though remarkable improvement was seen after 6months of VNS treatment (p<0.05), no further changes were observed in 12-month compared with 6-month levels (p>0.05) in all parameters, still even significantly lower than those of controls (p<0.05). Longer duration of epilepsy and localization of epileptic focus, such as in the temporal lobe, were also found to further contribute to diminished basal HRV levels (p<0.05).

CONCLUSION

The cardiovascular system is under deep sympathetic influence in children with epilepsy. Although VNS seems to provide a substantial improvement by achieving increased parasympathetic effects in short-term therapy, the levels were still lower than those of healthy children after either short- or long-term therapy. Therefore, impaired cardiovascular autonomic regulation may be associated with the epileptic process itself as well as with the contribution of some additional factors. Overall, different aspects such as age, epilepsy duration, epileptic focus, seizure frequency, and AEDs should also be considered for their further possible effects on HRV during VNS therapy.

Changes in sleep patterns after vagus nerve stimulation, deep brain stimulation or epilepsy surgery: Systematic review of the literature

PURPOSE

Perform a systematic review of the literature on the effects of vagus nerve stimulation (VNS), deep brain stimulation (DBS) and epilepsy surgery in subjective and objective sleep parameters.

METHODS

We performed a literature search in the main medical databases: Medline, Embase, Cochrane, DARE and LILACS, looking for studies that evaluated the effects of VNS, DBS or epilepsy surgery on sleep parameters. In all, 36 studies, coming from 11 countries, including reviews, cohort studies, case series and case reports were included.

RESULTS

VNS induces sleep apnoea dependent of the stimulation variables. This condition can be reverted modifying these settings. Surgical procedures for epilepsy cause an improvement in objective and subjective sleep parameters that depend on the success of the procedure evaluated through ictal frequency control. There is evidence that non-pharmacologic treatment of epilepsy has different effects on sleep patterns.

CONCLUSION

It is advisable to include objective and subjective sleep parameters in the initial evaluation and follow-up of patients considered for invasive procedures for epilepsy control, especially with VNS due to the risk of sleep apnoea. More high quality studies are needed.

The Mutual Interaction Between Sleep and Epilepsy on the Neurobiological Basis and Therapy

BACKGROUND

Sleep and epilepsy are mutually related in a complex, bidirectional manner. However, our understanding of this relationship remains unclear.

RESULTS

The literatures of the neurobiological basis of the interactions between sleep and epilepsy indicate that non rapid eye movement sleep and idiopathic generalized epilepsy share the same thalamocortical networks. Most of neurotransmitters and neuromodulators such as adenosine, melatonin, prostaglandin D2, serotonin, and histamine are found to regulate the sleep-wake behavior and also considered to have antiepilepsy effects; antiepileptic drugs, in turn, also have effects on sleep. Furthermore, many drugs that regulate the sleep-wake cycle can also serve as potential antiseizure agents. The nonpharmacological management of epilepsy including ketogenic diet, epilepsy surgery, neurostimulation can also influence sleep.

CONCLUSION

In this paper, we address the issues involved in these phenomena and also discuss the various therapies used to modify them.

A Potential Novel Mechanism for Vagus Nerve Stimulator-Related Central Sleep Apnea

The treatment of epilepsy with vagus nerve stimulation can inadvertently cause obstructive and central sleep apnea (CSA). The mechanism for CSA seen in patients with a vagus nerve stimulator (VNS) is not fully known. We describe the case of a 13-year-old girl in whom VNS activation induced tachypnea and post-hyperventilation central apnea. Following adjustment of VNS settings, the post-hyperventilation CSA resolved. Polysomnography may assist with management when patients with epilepsy develop sleep disruption after VNS placement.

The heart side of brain neuromodulation

Neuromodulation refers to invasive, minimally invasive or non-invasive techniques to stimulate discrete cortical or subcortical brain regions with therapeutic purposes in otherwise intractable patients: for example, thousands of advanced Parkinsonian patients, as well as patients with tremor or dystonia, benefited by deep brain stimulation (DBS) procedures (neural targets: basal ganglia nuclei). A new era for DBS is currently opening for patients with drug-resistant depression, obsessive-compulsive disorders, severe epilepsy, migraine and chronic pain (neural targets: basal ganglia and other subcortical nuclei or associative fibres). Vagal nerve stimulation (VNS) has shown clinical benefits in patients with pharmacoresistant epilepsy and depression. Non-invasive brain stimulation neuromodulatory techniques such as repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) are also being increasingly investigated for their therapeutic potential in several neurological and psychiatric disorders. In this review, we first address the most common neural targets of each of the mentioned brain stimulation techniques, and the known mechanisms of their neuromodulatory action on stimulated brain networks. Then, we discuss how DBS, VNS, rTMS and tDCS could impact on the function of brainstem centres controlling vital functions, critically reviewing their acute and long-term effects on brain sympathetic outflow controlling heart function and blood pressure. Finally, as there is clear experimental evidence in animals that brain stimulation can affect autonomic and heart functions, we will try to give a critical perspective on how it may enhance our understanding of the cortical/subcortical mechanisms of autonomic cardiovascular regulation, and also if it might find a place among therapeutic opportunities in patients with otherwise intractable autonomic dysfunctions.

The therapeutic dilemma of vagus nerve stimulator-induced sleep disordered breathing

Intermittent vagus nerve stimulation (VNS) can reduce the frequency of seizures in patients with refractory epilepsy, but can affect respiration in sleep. Untreated obstructive sleep apnea (OSA) can worsen seizure frequency. Unfortunately, OSA and VNS-induced sleep disordered breathing (SDB) may occur in the same patient, leading to a therapeutic dilemma. We report a pediatric patient in whom OSA improved after tonsillectomy, but coexistent VNS-induced SDB persisted. With decrease in VNS output current, patient's SDB improved, but seizure activity exacerbated, which required a return to the original settings. Continuous positive airway pressure titration was attempted, which showed only a partial improvement in apnea–hypopnea index. This case illustrates the need for clinicians to balance seizure control and SDB in patients with VNS.

Primary sleep disorders in people with epilepsy: clinical questions and answers

The questions facing clinicians with patients with sleep disorder and epilepsy are addressed in this article. Both adult and child epilepsy are discussed in the context of the most typical questions a clinician would have, such as "Are parasomnias more common in people with epilepsy?", "Is sleep architecture abnormal in children with epilepsy", along with outcomes of numerous questionnaire-based, case-based, and double-blind placebo studies on such aspects as sleep duration, daytime sleepiness, anxiety and fears, limb movement, nocturnal seizures, agitation, behavioral disorders, and learning disorders.

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

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

Non-respiratory indications for polysomnography and related procedures in children: an evidence-based review

OBJECTIVE

This evidence-based review provides a systematic and comprehensive review of the literature regarding the utility of polysomnography for the evaluation of non-respiratory sleep disorders in children including hypersomnias, parasomnias, sleep-related movement disorders, and sleep in other special populations.

METHODS

A task force of pediatric sleep medicine experts performed a systematic review of the literature regarding the use of polysomnography for non-respiratory sleep disorders in children. They identified and graded 76 papers as evidence.

RESULTS

The main results include (1) polysomnography combined with the multiple sleep latency test is useful for evaluating disorders of excessive somnolence to objectively quantify sleepiness. The results have to be interpreted with consideration of the pubertal stage and regularity of the sleep patterns of the child; (2) polysomnography is indicated in children with parasomnias or sleep related movement disorders who have a high likelihood of having obstructive sleep apnea (OSA); (3) polysomnography is not routinely indicated in children with enuresis unless there is a high likelihood of OSA; (4) polysomnography can be helpful in evaluating children with restless legs syndrome (RLS) and when periodic limb movement disorder (PLMD) is suspected.

CONCLUSIONS

These findings suggest that, in children with non-respiratory sleep disorders, polysomnography should be a part of a comprehensive sleep evaluation in selected circumstances to determine the nature of the events in more detail or when the suspicion of OSA is relatively high.

Obstructive sleep apnea and respiratory complications associated with vagus nerve stimulators

Intermittent vagus nerve stimulation can reduce the frequency of seizures in patients with refractory epilepsy. Stimulation of vagus nerve afferent fibers can also cause vocal cord dysfunction, laryngeal spasm, cough, dyspnea, nausea, and vomiting. Vagus nerve stimulation causes an increase in respiratory rate, decrease in respiratory amplitude, decrease in tidal volume, and decrease in oxygen saturation during periods of device activation. It usually does not cause an arousal, or a change in heart rate or blood pressure. Most patients have an increase in their apnea-hypopnea index (AHI). Patients with VNS can have central apneas, obstructive hypopneas, and obstructive apneas. These respiratory events can be reduced with changes in the vagus nerve stimulator operational parameters or with the use of CPAP. In summary, there are complex relationships between epilepsy and obstructive sleep apneas. In particular, patients with refractory epilepsy need assessment for undiagnosed and untreated obstructive sleep apnea before implantation of vagus nerve stimulator devices. Patients with vagus nerve stimulators often have an increase in apneic events after implantation, and these patients need screening for sleep apnea both before and after implantation.