Right-sided Vagus Nerve Stimulation as a Treatment for Refractory Epilepsy in Humans

Vagus nerve stimulation for epilepsy and depression

Many patients with epilepsy suffer from persistent seizures despite maximal antiepileptic drug (AED) therapy. Chronic, intermittent vagus nerve stimulation (VNS) has proven to be a safe, effective option for patients suffering from refractory seizures who are not candidates for surgical resection. Although only a small minority of patients will be entirely seizure-free, VNS as an adjunct to medical therapy does appear to provide a significant amount of improvement in quality of life. Reports of antidepressant effects independent of seizure control, along with the use of multiple AEDs in the treatment of depression, has led to the investigation of VNS as a potential adjunctive treatment for major depressive disorder. Both the number of severely depressed patients refractory to available pharmacologic options and the need for repeated treatments and significant side effects associated with electroconvulsive therapy have heightened the interest in VNS for this patient population. Pilot studies of VNS for depression have shown impressive response rates; however, the effect appears to be gradual in onset, as demonstrated by the lack of a favorable response in a short-term, randomized controlled study. Investigation is thus needed to establish the potential role of VNS as an adjunctive treatment for severe depression.

Vagus nerve stimulation in children with refractory epilepsy: unusual complications and relationship to sleep-disordered breathing

BACKGROUND

Vagus nerve stimulation (VNS) is approved for use in patients with refractory epilepsy over the age of 12 years. While this procedure is widely used, there is little data on adverse events in young children.

MATERIALS AND METHODS

A retrospective chart review was conducted on 26 children who had VNS implantation for refractory epilepsy from 1998 to 2004.

RESULTS

Ages ranged from 3 to 17 years (16 boys and 10 girls). Seventy-seven percent had moderate to severe mental retardation. Sixty-five percent had more than 30 seizures per month. Symptomatic-generalized epilepsy was the predominant epilepsy syndrome seen in 77% of children. The duration of VNS treatment ranged from 1 month to 8 years (mean = 3.5 years). Twenty of 26 patients (77%) were on rapid-cycling mode. More than 50% reduction in seizure frequency was noted in 54% with two patients achieving seizure freedom. Twenty-three percent had less than 50% seizure reduction. Four patients were able to terminate seizures with use of the magnet. VNS was removed from one patient because of intractable cough persisting in spite of stimulation being turned off for 1 month. Another patient had it removed twice for infection. Obstructive sleep apnea (OSA) was observed in four patients (15%) after placement of VNS.

CONCLUSION

VNS appears to be an effective treatment for children with refractory epilepsy. Development of intractable cough in one patient in spite of device being turned off and recurrent infection-related removal in another are unusual complications. Polysomnography before implantation of VNS should be considered to identify patients with pre-existing OSA.

Finding the missing link between ictal bradyarrhythmia, ictal asystole, and sudden unexpected death in epilepsy

Basic science studies of the human brain have supported the cortical representation of cardiovascular responses, including heart rate variability. Clinical observations of ictal bradyarrhythmia may be mechanistically explained by the influence of the central autonomic network, although the localization and lateralization issues need to be considered in the light of patterns of seizure spread, hand dominance, and presence of lesions. Ictal bradyarrhythmia also offers a mechanistic explanation of sudden unexpected death in epilepsy (SUDEP), though it may explain only some but not all cases of SUDEP. The missing links are (1) clinical evidence of common factors shared by patients with ictal bradyarrhythmia and patients who die from SUDEP, (2) evidence of arrhythmia as a risk factor for SUDEP from epidemiological studies, and, (3) determination of the importance of ictal bradyarrhythmia in SUDEP with respect to other proposed mechanisms including apnea and intrinsic cardiac abnormalities. There remains a need to review the seizure mechanisms in cases of SUDEP and to step up the amount of concurrent ECG/intracranial EEG analysis in both ictal bradyarrhythmia and SUDEP cases.

Vagal nerve stimulation for refractory epilepsy in children: indications and experience at The Hospital for Sick Children

OBJECTIVES

The management of intractable epilepsy in children is a challenging problem. For those patients who do not respond to antiepileptic drugs and are not candidates for epilepsy surgery, vagal nerve stimulation (VNS), can be a viable alternative for reducing seizure frequency. We have reviewed the historical and clinical background of VNS treatment. We also include our experience at The Hospital for Sick Children in children who underwent VNS implantation.

METHODS

Forty-one children underwent VNS implantation for epilepsy over 6 years. After a mean follow-up of 31 months, 15 (38%) patients had a seizure frequency reduction of more than 90%. Fifteen (38%) children failed to respond to the VNS treatment. The device was removed in five children: in one, due to late infection; the other four could not tolerate the side effects of chronic VNS therapy. Two patients required reimplantation due to electrode failure. The most common side effects in our series were cough and vocal disturbances.

CONCLUSIONS

Our results show that VNS implantation can be a safe and effective alternative therapy for children with drug-resistant epilepsy who are not candidates for epilepsy surgery.

The use of a sump antibiotic irrigation system to save infected hardware in a patient with a vagal nerve stimulator

The authors describe the use of a sump irrigation system that was used to successfully treat the battery implantation site of a vagal nerve stimulator (VNS). Irrigation was composed of a dilution of vancomycin in lactated Ringer's solution. At long-term follow up, the patient has not returned with signs or symptoms of wound infection. She continues to effectively combat her epilepsy with VNS. The authors believe this to be the first description of this technique for salvaging an implanted VNS.