Neurostimulation Therapies for Epilepsy: From Vagus Nerve Stimulation to Responsive Neurostimulation

Shenglin Jiang^*
*Correspondence: Shenglin Jiang, Department of Neurology, University of Arkansas for Medical Sciences, Little Rock, AR, USA, Email:

Introduction

Epilepsy is a neurological disorder characterized by recurrent seizures, affecting millions of people worldwide. Despite the availability of antiepileptic drugs, a significant number of patients do not achieve complete seizure control. For these individuals, neurostimulation therapies offer an alternative approach to managing epilepsy. Among these therapies, Vagus Nerve Stimulation (VNS) and Responsive Neurostimulation (RNS) have emerged as promising options. Vagus Nerve Stimulation (VNS) is a neurostimulation therapy designed to help manage epilepsy, particularly in patients who have not achieved sufficient seizure control with Antiepileptic Drugs (AEDs). Approved by the U.S. Food and Drug Administration (FDA) for epilepsy treatment, VNS involves the implantation of a device that sends electrical impulses to the vagus nerve, which runs from the brainstem to the abdomen.

Vagus Nerve Stimulation is one of the earliest and most established neurostimulation therapies for epilepsy. It involves implanting a small device, similar to a pacemaker that stimulates the vagus nerve, which runs from the brainstem to the abdomen. The VNS device is implanted under the skin in the chest area, with a lead attached to the left vagus nerve in the neck. The device delivers regular, mild electrical pulses to the vagus nerve. These pulses are thought to influence brain activity, potentially reducing the frequency and severity of seizures. VNS therapy begins with a surgical procedure to implant a small pulse generator under the skin in the chest area and attach a lead to the left vagus nerve in the neck. The procedure is typically performed under general anesthesia [1,2]. The pulse generator is a battery-powered device that generates electrical impulses. The lead is wrapped around the vagus nerve to deliver these impulses.

Description

The device is programmed to deliver regular, mild electrical pulses to the vagus nerve. The frequency and duration of these pulses can be adjusted based on the patient's needs. Some VNS systems allow patients to activate stimulation manually using an external magnet when they sense a seizure is about to occur, although this feature's efficacy can vary. The exact mechanism by which VNS affects seizure activity is not fully understood, but it is believed to modulate neural circuits in the brain involved in seizure generation. The stimulation may enhance neurotransmitter release, alter neuronal excitability and improve overall brain function. Clinical studies have shown that VNS can reduce the frequency of seizures by about 40-50% in many patients. Some individuals may experience more significant reductions and a small percentage achieves complete seizure freedom. Beyond reducing seizures, VNS may improve overall quality of life.

Patients often report better mood, cognitive function and reduced frequency of seizure-related emergencies. VNS is generally well-tolerated. Common side effects include mild hoarseness, throat irritation, cough and a tingling sensation in the neck. These side effects often diminish over time. Long-term studies indicate that VNS is safe for prolonged use, with few severe complications. VNS is typically considered for patients who have drug-resistant epilepsy and are not candidates for surgical resection or other interventions. The suitability of VNS is evaluated based on the patient’s seizure type, frequency and overall health condition [3,4]. Vagus Nerve Stimulation (VNS) offers a valuable alternative for managing epilepsy, particularly in cases where traditional medications are insufficient. With its ability to reduce seizure frequency and improve quality of life, VNS represents a significant advancement in the treatment of epilepsy. As technology and research continue to evolve, VNS therapy is likely to become even more effective and tailored to individual patient needs, providing hope and improved outcomes for many living with epilepsy.

VNS is typically considered for patients who have not responded well to AEDs and are not candidates for surgical resection. The device requires a surgical procedure for implantation and regular maintenance, including battery replacement. Responsive Neurostimulation (RNS) is a newer and more advanced neurostimulation therapy. It involves implanting a device that not only stimulates the brain but also detects and responds to abnormal electrical activity in real-time. The RNS device is implanted in the skull, with electrodes placed on or within the brain’s seizure focus. It continuously monitors brain activity. When the device detects patterns indicative of an impending seizure, it delivers electrical stimulation to the targeted brain areas to prevent the seizure from fully developing. Targeted Intervention: RNS offers a tailored approach by stimulating only when necessary, potentially reducing seizures more effectively. The device provides continuous monitoring and adjustment, allowing for a more responsive and dynamic treatment approach.

Clinical trials have shown that RNS can significantly reduce seizure frequency in about 40-60% of patients, with some achieving complete seizure freedom. RNS is typically used for patients with focal epilepsy who have not achieved adequate control with AEDs and are not candidates for resection. The implantation procedure is more complex than VNS, involving precise placement of electrodes. Long-term device management and followup are required to adjust stimulation parameters and monitor efficacy. Both VNS and RNS represent significant advancements in the management of epilepsy, but ongoing research continues to explore their potential and refine their applications [5]. Emerging studies focus on optimizing stimulation parameters, understanding patient selection criteria and integrating these therapies with other treatment modalities. Research is exploring closed-loop systems that use advanced algorithms to predict and respond to seizures with greater precision.

Conclusion

Neurostimulation therapies, including Vagus Nerve Stimulation (VNS) and Responsive Neurostimulation (RNS), offer valuable options for individuals with epilepsy who do not achieve adequate seizure control with medications alone. VNS provides a proven and well-established approach, while RNS offers a more sophisticated, responsive mechanism for managing seizures. As research continues to advance, these therapies are likely to become even more effective and tailored to individual patient needs, offering hope and improved quality of life for those affected by epilepsy. Combining neurostimulation with other treatments, such as AEDs or cognitive behavioral therapy, may offer enhanced benefits. Advances in neuroimaging and genetic research may lead to more personalized and effective neurostimulation strategies.

Acknowledgement

None.

Conflict of Interest

None.

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